Appendix:Dictionary of Mining, Mineral, and Related Terms/C/6

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Said of igneous rocks that have a common set of chemical and mineralogic features, and thus are regarded as having been derived from a common parent magma. See also: consanguinity. Syn: consanguineous.

comagmatic region

An area in which the igneous rocks are of the same general geologic age, have certain distinguishing characteristics in common, and are regarded as comagmatic. Syn: petrographic province.


In a fissure that has been filled by successive deposits of minerals on the walls, the place where two sets of layers thus deposited approach most nearly or meet, closing the fissure and exhibiting either a drusy central cavity or an interlocking of crystals. See also: comb texture.

comb dung

See: comedown.

combed structure

In its simplest form this structure consists of a fissure lined with crystals on each side, having their bases on the walls and their apexes directed toward the center. In some cases the fissure is thus altogether filled up with two sets of crystals meeting in the center.


A trigonal mineral, Na (sub 2) Ca (sub 2) Si (sub 3) O (sub 9) ; in nephelinite at Kivu, Republic of the Congo.

combination drill

A drill equipped for cable-tool and/or diamond-drilling operations, or for a cable-tool and/or rotary drilling operations. Syn: combination rig.

combination electric locomotive

A mine locomotive that can operate as a trolley locomotive or as a battery locomotive. While operating on a battery, it can be used, under certain conditions, at the coal face. Also it may be used on the main haulage trolley system where, due to higher voltage, higher speeds are possible.

combination longwall

See: longwall.

combination process

Method for extracting alumina from high-silica bauxites, in which the bauxite is first subjected to a Bayer process caustic leach. The resulting red mud, containing sodium aluminum silicate, is sintered with limestone plus soda ash and then leached with water to recover alumina and soda.

combination rig

a. A rig comprising a complete cable-tool outfit and a complete rotary outfit.

b. See: combination drill.

combination sampler

A universal-type soil-sampling device in which some of the constructional features of two or more special-use samplers are combined.

combination stoping

See: combined overhand and underhand stoping.

combined carbon

The part of the total carbon in steel or cast iron that is present as other than free carbon.

combined moisture

Moisture in coal that cannot be removed by ordinary drying. CF: free moisture.

combined overhand and underhand stoping

This term signifies the workings of a block simultaneously from the bottom to its top and from the top to the bottom. The modifications are distinguished by the support used, as open stopes, stull-supported stopes, or pillar-supported stopes. Also known as combined stopes; combination stoping; overhand stoping and milling system. Syn: back and underhand stoping milling system; combination stoping.

combined shrinkage stoping and caving

In this method, the orebody is worked from the top down in successive layers of much greater thickness than in top slicing. The mass of ore is weakened by a series of shrinkage stopes, which are extended up between the ribs, pillars, or blocks, which are subsequently caved. The intervening blocks are under cut and caved as in block caving. The caver follows the caved ore. Also called overhand stoping with shrinkage and simultaneous caving.

combined side and longwall stoping

See: overhand stoping.

combined stresses

Any state of stress that cannot be represented by a single component of stress; i.e., one that is more complicated than simple tension, compression, or shear.

combined top slicing and shrinkage stoping

In this method, the orebody is worked from the top down in successive slices. In the working of each slice, the unit is worked as a shrinkage stope. The broken ore serves to give lateral support to the sides of the unit and also serves as a working platform from which the back is reached. After working a unit, the cover is caved. No timber mat is used. Also known as the Kimberley method.

combined twinning

A rare type of twinning in quartz in which there appears to be a 180 degrees rotation around c with reflection over (1120) or over (0001). The crystal axes are parallel, but the polarity of the a axis is not reversed in the twinned parts.

comb texture

A texture in which individual crystals have their long axis perpendicular to the walls of a vein. See also: comb.

combustible gases cap

A small cap that forms over the flame of a safety lamp when sufficient combustible gases (methane) are present.

combustible gases drainage

The collection of combustible gases from coal measures strata, generally into pipes, with or without the use of suction. See also: methane drainage.

combustible gases fringe

The zone of contact between the goaf gases and the ventilation air current at the face.

combustible gases layer

A sheetlike accumulation of combustible gases under the roof of a mine roadway where the ventilation is too sluggish to dilute and remove the gas. Although the term is new, the hazard existed since the earliest days of coal mining. A combustible gases layer may be specified as one in which the gas is 5% or over and of a length greater than the width of the road in which it occurs. See: pocket of gas. See also: stratification of methane.

combustible shale

See: tasmanite.

combustion arch

A flat or curved refractory roof over a furnace to promote combustion by reflection of heat.

combustion engineer

An engineer with practical training and knowledge of all kinds of fuels and their combustion characteristics. In general, the engineer lacks the technical qualifications of the fuel technologist.

combustion method

A method for the quantitative determination of certain elements (such as carbon, hydrogen, and nitrogen) in organic compounds by combustion.


Softish stone occurring in the roof of a coal seam; it easily falls when coal is removed. Syn: comb dung.


A sodic rhyolite containing alkalic amphibole and/or pyroxene.

come out

To withdraw or hoist the drill string or tools from a borehole.

come water

The constant or regular flow of water in a mine proceeding from old workings or from water-bearing rocks.

comfort air conditioning

Air conditioning that controls the atmosphere that human beings breathe.

coming up to grass

Eng. Common terms used by miners for the word basset, or outcrop. Also coming up today.


Lower Cambrian.

commercial deposit

A deposit of oil, gas, or other minerals in sufficient quantity for production in paying quantities.

commercial explosives

Explosives designed, produced, and used for commercial or industrial applications rather than for military purposes.

commercial granite

A general term for a decorative building stone that is hard and crystalline. It may be a granite, gneiss, syenite, monzonite, granodiorite, anorthosite, or larvikite. See also: black granite.

commercially disposable coal

A statistical term referring to saleable coal, less colliery consumption and coal supplied to employees.

commercial marble

A crystalline rock composed predominantly of one or more of the following minerals: calcite, dolomite, or serpentine, and capable of being polished.

commercial mine

A mine operated to supply purchasers in general as contrasted with a captive mine.

commercial ore

Can. Mineralized material currently profitable at prevailing prices.

commercial quantity

A quantity of oil, gas, or other minerals sufficient for production in paying quantities.

commercial quarry

a. Term that includes quarries for aggregate and quarries for the production of limestone for industrial and agricultural purposes.

b. Not owned or controlled by consumer. Contrasted with a captive quarry.

commercial sampling of coal

Procedures intended to produce an accuracy such that if a large number of samples are taken from a single lot of coal, 95 out of 100 test results will be within + or - 10% of the average of these samples.


a. The gradual diminution of a substance to a fine powder or dust by crushing, grinding, or rubbing; specif., the reduction of a rock to progressively smaller particles by weathering, erosion, or tectonic movements.

b. The breaking, crushing, or grinding by mechanical means of stone, coal, or ore, for direct use or further processing. Syn: pulverization; trituration.

common banded coal

See: banded coal.

common feldspar

See: orthoclase.

common ion effect

Change in concentration of an ion in a saturated solution through addition of another electrolyte that yields an ion in common with the solid substance present in excess. The ion product remains constant, but with the increase of concentration of one ion that of the other diminishes correspondingly. Since the solution is already saturated, precipitation occurs, the effect being a reversal of the process of ionization.

common lead

Lead (Pb) having four isotopes (mass numbers 204, 206, 207, and 208) in the proportions generally obtained by analyzing lead from rocks and lead minerals that are associated with little or no radioactive material; commonly considered to be the lead present at the time of the Earth's formation, as distinguished from lead produced later by radioactive decay.

common mica

See: muscovite.

common opal

Opal without play of color. Most varieties are of no gemological interest or importance; others because of their color or markings are set in jewelry. CF: precious opal.

common pyrite

See: pyrite.

commutated current

Electric current of constant strength of which the direction of flow is reversed at constant intervals of time.

compacted yards

Measurement of soil or rock after it has been placed and compacted in a fill.

compaction curve

The curve showing the relationship between the density (dry unit weight) and the water content of a soil for a given compactive effort. Syn: moisture-density curve.

compaction equipment

Machines, such as rollers, to expel air from a soil mass and so achieve a high density. Smooth-wheel rollers are best for gravels, sands, and gravels-and-clay soils with reasonably high moisture contents. Pneumatic-tired rollers are best for clays with reasonably high moisture content, and sheepsfoot rollers are the best for clays with low moisture content. See also: superficial compaction.

compaction test

A laboratory compacting procedure to determine the optimum water content at which a soil can be compacted so as to yield the maximum density (dry unit weight). The method involves placing (in a specified manner) a soil sample at a known water content in a mold of given dimensions, subjecting it to a compactive effort of controlled magnitude, and determining the resulting unit weight (ASCE, 1958, term 74). The procedure is repeated for various water contents sufficient to establish a relation between water content and unit weight. The maximum dry density for a given compactive effort will usually produce a sample whose saturated strength is near maximum. Syn: moisture-density test.

compact rock

A rock so closely grained that no component particles or crystals can be recognized by the eye.

company account

Drilling done by a company on its property using its own equipment operated by personnel working for the company.


a. In photographic mapping, a device for measuring accurately the two rectangular coordinates of the image of a point on a photograph.

b. An apparatus facilitating comparison of test material with known standard, or with other substances. A comparator miscroscope has a duplicate optical system, so that the observer sees two fields simultaneously (one with each eye). The Lovibond comparator has colored disks that can be matched against colored liquids to give approximate pH value, etc., using the same principle as with a set of pH color tubes in a more permanent and compact style.

comparator tintometer

Instrument in which color of test solution is compared with that of reference cell or tinted glass slide. Also called colorimeter.

comparison prism

A small, right-angled prism placed in a front of a portion of the slit of a spectroscope or a spectrograph for the purpose of reflecting light from a second source of light into the collimator, so that two spectra may be viewed simultaneously.

compass direction

Direction as indicated by a compass without any allowances for compass error. The direction indicated by a magnetic compass may differ by a considerable amount from the true direction referred to a meridian of the Earth.

compensating error

Random error equally likely to be plus or minus, and if of small dimensions, reasonably likely to be compensated by further errors. In contrast, systematic or biased errors all fall on the same side of correct measurement and may therefore accumulate and produce serious discrepancies.

compensating rope

Balance weight ropes having direct connection with hoisting ropes.

compensation method

A procedure for determining the voltage difference between two points in the ground by balancing against a voltage that is adjusted in phase and amplitude to effect the compensation. See also: compensator.


An instrument to determine the voltage difference between two points in the ground by the compensation method. Syn: accessory plate.


The ability of a current of water or wind to transport detritus, in terms of particle size rather than amount, measured as the diameter of the largest particle transported. It depends on velocity: a small, but swift stream, e.g., may have greater competence than a larger but slower-moving stream. Adj: competent.


a. Strata or rock structure combining sufficient firmness and flexibility to transmit pressure and, by flexure under thrust, to lift a superincumbent load.

b. Streams able to transport debris of a given size. c. Rock formations in which no artificial support is needed to maintain a cave-free borehole. d. Rock capable of withstanding an applied load under given conditions without falling or collapsing. See also: incompetent.

competent bed

a. A rock formation that, because of massiveness or inherent strength, is able to lift not only its own weight but also that of the overlying rock.

b. A bed that has a physical characteristic such that it responds to tectonic forces by folding and faulting, rather than by crushing and flowing. A competent bed is relatively strong, an incompetent bed, relatively weak. See also: incompetent bed.

competent rock

a. Rock that, because of its physical and geological characteristics, is capable of sustaining openings without structural support, except pillars and walls left during mining.

b. Rock formations in which no artificial support is needed to maintain a cave-free borehole. c. Rock capable of withstanding an applied load under given conditions without falling or collapsing.


See: rock fracture.

complementary dikes

Associated dikes (or other minor intrusions) composed of different, but related rocks, regarded respectively as leucocratic and melanocratic differentiation products from a common magma; e.g., aplite and lamprophyre; bostonite and camptonite.

complementary forms

In crystallography, two forms combined geometrically to produce a form having higher symmetry; e.g., two equally developed rhombohedra of quartz resembling a hexagonal bipyramid.

complete combustion

Occurs when the products of combustion leaving the furnace or appliance do not contain any gaseous combustible matter.


a. A large-scale field association or assemblage of different rocks of any age or origin, having structural relations so intricately involved or otherwise complicated that the rocks cannot be readily differentiated in mapping, e.g., a volcanic complex. See also: igneous complex; basement complex.

b. A unit that consists of a mixture of rocks of two or more genetic classes, i.e., igneous, sedimentary, or metamorphic, with or without highly complicated structure; example: Franciscan Complex. c. Said of an ore that carries several metals difficult to extract. d. An assemblage of rocks of any age or origin that has been folded together, intricately mixed, involved, or otherwise complicated.

complex crystals

Those having many crystal forms and faces.

complex fold

A fold that is cross-folded; i.e., a fold, the axial line of which is folded.

complex ore

a. An ore containing two or more metals, as lead-zinc ore. Many complex ores are difficult or costly to treat, e.g., gold ore with arsenic or antimony minerals, or ore composed almost entirely of several sulfide minerals.

b. An ore containing several metals. c. Ores named for two or more valuable metals such as lead-zinc ores, gold-silver ores, etc. d. This term has no precise meaning. It generally signifies an ore that is difficult or costly to treat because of the presence of unusual minerals, e.g., a gold ore with aresenic and antimony minerals, or an ore containing two or more metals, or ore composed almost wholly of several sulfide minerals.

complex pegmatite

A pegmatite body characterized by pneumatolytic-hydrothermal replacement and rare minerals.

complicated pneumoconiosis

A condition superimposed on simple pneumoconiosis by the effect of tuberculosis lesions.

component of coal

Layers or bands that are petrographic entities, recognizable visually as bands or layers of coal that have distinctive physical appearance and characteristic microstructural features from coal to coal.

composite dike

A dike formed by two or more intrusions of different compositions into the same fissure.

composite explosives

Explosives that contain a mechanical mixture of substances that consume and give off oxygen with one or several simple explosives. They can be regarded as mixed explosives with an addition of one or more simple explosives as sensitizers, which makes for easier initiation of the mixture and gives greater assurance of complete transformation.

composite fold

See: compound fold.

composite gneiss

a. A banded rock resulting from intimate penetration of magma (usually granite) into adjacent rocks. See also: injection gneiss; migmatite.

b. Gneiss that is constituted of materials of at least two different phases. CF: venite; veined gneiss.

composite intrusion

Any igneous intrusion that is composed of two or more injections of different chemical and mineralogical composition. CF: multiple intrusion.

composite map

A map on which several levels of a mine are shown on a single sheet. Horizontal projection of data from different elevations.

composite materials

Structural materials of metal alloys or plastics with built-in strengthening agents that may be in the form of filaments, foils, or flakes of a strong material.

composite sampling scheme

One in which different parts, or stages, of the sample are reached by differing methods.

composite sill

A sill composed of two or more intrusions having different chemical and mineralogical compositions.

composite stone

See: assembled stone.

composite stones

A comprehensive term that includes doublets, triplets, etc., in which a stone consists of two or more parts either of the same or of different materials cemented or otherwise joined together.

composite vein

A large fracture zone, up to many tens of feet in width, consisting of parallel ore-filled fissures and converging diagonals, the walls and the intervening country rock of which have undergone some replacement.

Composition B

A mixture of RDX and TNT that, when cast, has a density of 1.65 g/cm (super 3) and a velocity of 25,000 ft/s (7.6 km/s). It is useful as a primer for blasting agents.

composition of forces

If two or more forces acting on a body can be replaced by a single force the forces are said to have been compounded. This is known as composition of forces.

composition surface

A planar or irregular surface by which parts of a twin crystal are united, not necessarily parallel to a crystal face.

compound compression

In compound compression, the work of compression is divided into two or more stages or cylinders. In two-stage compression, air is compressed in the first or low-pressure cylinder to a certain point, then forced into an intercooler where it is cooled to approx. its original temperature, then passes into the second or high-pressure cylinder, in which it is compressed to the final or delivery pressure. The ratio of compression in each cylinder of a two-stage compressor is equal to the square root of the overall ratio of compression, i.e., the square root of the final absolute pressure divided by the absolute atmospheric pressure. In three-stage work, the ratio of compression in each cylinder is the cube root of the overall ratio of compression. Also called stage compression.

compound cradle

An apparatus comprising three tiers of blanket tables, a shaking table, and a mercury riffle for catching gold.

compound dredger

A type of dredger combining the suction or suction cutter apparatus with a bucket ladder.

compound fault

A series of closely spaced parallel or nearly parallel faults.

compound fold

A fold upon which minor folds with similar axis have developed. Syn: composite fold.

compound lode

See: compound vein.

compound shaft

A shaft in which the upper stage is often a vertical shaft, while the lower stage, or stages, may be inclined and driven in the deposit. In this type of shaft, underground winding engines are installed to deal with the lower stages, with transfer points and ore bins at the junction of two stages.

compound twins

In crystallography, individual crystals of one group united according to different laws.

compound vein

a. A vein or lode consisting of a number of parallel fissures united by cross fissures, usually diagonally.

b. A vein composed of several minerals. Syn: compound lode.

compound ventilation

a. An arrangement of a number of major ventilation systems serving various large working areas and served by more than two shafts and their associated fans, but integrated to form one ventilation system. Usually adopted in large combined mines. See also: radial ventilation.

b. Ventilation by means of a number of splits, which is now normal practice. See also: ventilation.

compressed air

Air compressed in volume and transmitted through pipes for use as motive power for underground machines. Compressed air is costly to transmit long distances, but has certain advantages, namely, it cools the air at the working face and is relatively safe in gassy mines. See also: air-conditioning process.

compressed-air blasting

A method originated in the United States for breaking down coal by compressed air. Air at a pressure of 10,000 to 12,000 psi (69 to 83 MPa) is conveyed in a steel pipe to a tube- or shell-inserted shothole. The air is admitted by opening a shooting valve and is released in the hole by the rupture of a shear pin or disk. The sudden expansion of the air in the confined hole breaks down the coal. Syn: Armstrong air breaker. See also: Airdox.

compressed-air-driven lamps

These lamps are self-contained units and comprise a strong alloy casing within which are a compressed-air turbine and a small alternating-current generator with stationary windings and revolving field magnets. The air enters the casing at one side, passes through a filter and then through a reducing valve that maintains a constant pressure of 40 psi (276 kPa) on the turbine blades. The air escaping from the turbine is used to scavenge the inside of the lamp and remove any combustible gases that might have entered when the lamp was not in use. It is finally discharged through a series of holes of such a size that the pressure inside the lamp casing is 2 to 3 psi (14 to 21 kPa) above atmospheric. Should this pressure be lost due to the lamp glass being broken, the light is extinguished automatically by a spring-loaded diaphragm, which short-circuits the generator unless held open by the excess pressure. Also called air turbolamp.

compressed-air locomotive

A mine locomotive driven by compressed air. It is very safe and is much used in gassy mines in Europe. The air is brought down by pipeline from the surface to a charging station near the pit bottom. See also: locomotive haulage.

compressed-air turbines

Turbines used for driving coal cutters, belt conveyors, and similar duties. They are not so efficient in their use of the air as piston engines, but possess the merits of extreme simplicity and robustness, and therefore are preferred for coal face use.

compressed pellets

Blasting powders manufactured in cartridge form for use in small diameter shotholes. These pellets are particularly useful for horizontal shotholes.


A system of forces or stresses that tends to decrease the volume or to shorten a substance, or the change of volume produced by such a system of forces.

compressional wave

a. A traveling disturbance in an elastic medium characterized by volume changes (and hence density changes) and by particle motion in the direction of travel of the wave.

b. A longitudinal wave (as a sound wave) propagated by the elastic compression of the medium. Syn: irrotational wave; pressure wave; P wave.

compression ratio

The ratio of the volume of space above a piston at the bottom of its stroke to the volume above the piston at the top of its stroke.

compression subsidence

That condition in sedimentation in which the flocs or particles are conceived to be in close contact, further subsidence occurring as a direct effect of compression resulting in the elimination of water from the flocs and interstitial spaces. The settling velocity decreases with time of settling.

compression zone

The surface area affected by compressive strain. CF: neutral zone; tension zone.

compressive strength

a. The maximum compressive stress that can be applied to a material, such as a rock, under given conditions, before failure occurs.

b. The load per unit area at which an unconfined prismatic or cylindrical specimen of soil will fail in a simple compression test. Syn: unconfined compressive strength.

compressive stress

A stress that tends to push together the material on sides of a real or imaginary plane. CF: tensile stress.


a. A machine, steam or electrically driven, for compressing air for power purposes. Small air compressors may be compound steam and double-stage air. Large compressors may be triple-expansion steam and three-stage air and are always used with condensers.

b. Any kind of reciprocating, rotary, or centrifugal pump for raising the pressure of a gas. c. A machine that compresses air.


An opaque variety of thompsonite from the Lake Superior region.


a. An automatic electronic device capable of accepting information, applying prescribed processes to it, and supplying the results of these processes. The term is generally used for any type of computer. See also: analog computer.

b. In seismic prospecting, one who with one or two assistants, carries on the routine work of transforming the "wiggly lines" on the reflection records into the form in which they are finally used. Where corrected record sections are prepared, he or she must compute the corrections and must assemble the other information to be fed into the playback so that it will turn out properly corrected records. In addition to handling corrections, the computer must mark the records, read and plot times, and otherwise maintain the flow of data. Such individuals are not used in processing modern digital seismic data.

computer-assisted mining

The process of controlling single or multiple mining machines in which sensors and computers are used to replace or enhance manual control of all or portions of the formerly manually controlled machine operations.


A mineral, (Mg,Cu,Zn)SO (sub 4) .5H (sub 2) O , containing 5.60% ZnO, 9.40% MgO, 9.00% CuO, and 39.07% H (sub 2) O ; from the Comstock Lode, NV. Syn: zinc-magnesia chalcanthite.

concave bit

A tungsten carbide drill bit for percussive boring. The cutting edge is concave, while in the conventional type the edge is convex. The new bit remains sharper for a longer period before regrinding becomes necessary and gives a higher penetration speed. Also called saddleback tip. See also: plug bit.

concave crown

See: concave bit.

concealed coalfield

A coalfield that is totally buried beneath newer deposits, usually Permian and Trias strata, which repose unconformably on the coal measures in the basin. A good example of a concealed coalfield is that of Kent, in southeast England. See also: coal basin; exposed coalfield.


The clean product recovered in froth flotation.

concentrated charge

a. The heavy explosive charge loaded into the enlarged chamber at the bottom of a quarry blasthole. See also: chambering.

b. Means that the height of the charge is small compared with the burden that can be given quantitatively.

concentrating plant

See: concentrator.

concentrating table

A device consisting of a riffled deck, usually inclined in two directions to the horizontal, to which a differential reciprocating motion in a substantially horizontal direction is imparted; the material to be separated is fed in a stream of water, the heavy particles collect between the riffles and are there conveyed in the direction of the reciprocating motion while the lighter particles are borne by the current of water over the riffles, to be discharged laterally from the table.


a. The ratio of the dry weight of sediment to the weight of water sediment mixture of which it is part. Sediment concentration is commonly expressed in parts per million (ppm).

b. Separation and accumulation of economic minerals from gangue. See also: ore dressing; preparation.

concentration cell

An electrolytic cell, the electromotive force of which is due to difference in concentration of the electrolyte or active metal at the anode and the cathode.

concentration criterion

The ratio between the density in a liquid of two minerals that are to be separated (M (sub h) and M (sub 1) being the heavy and light one, respectively); C = M (sub h) - 1/M (sub l) , where water (sp gr, 1) is the liquid. This ratio indicates the grain size above which separation by gravity methods should be commercially practicable. Above 2.5 fine sands (down to below 200 mesh) can be tabled. At 1.75 the lower limit is 100 mesh; at 1.5 about 10 mesh, and at 1.25 only gravel sizes can be treated.

concentration of output

Essentially, to secure the maximum output of coal from the minimum length of face with due regard to safety and development. To measure the degree of concentration at a colliery the following data are collected: (1) the total length of coalface; (2) the total length of main haulage roads; and (3) the total output. In general, the greater the dispersion of the workings, the greater the manpower employed and the higher the costs of production. See also: face concentration; geographical concentration; overall concentration.

concentration ratio

Weight or tonnage ratio (K) of the weight of feed (F) to the weight of concentration (C) produced: K = F/C, for a two-product treatment.

concentration table

A table on which a stream of finely-crushed ore and water flows downward; the heavier metallic minerals lag behind and flow off in a separate compartment.


a. A plant where ore is separated into values (concentrates) and rejects (tails). An appliance in such a plant, e.g., flotation cell, jig, electromagnet, shaking table. Also called mill; reduction works; cleaning plant. Syn: concentrating plant. CF: separator.

b. An apparatus in which, by the aid of water, air, and/or gravity, mechanical concentration of ores is performed. A concentration plant. c. A general term for a worker, who tends concentrating tables, vanners, and other types of equipment used to separate valuable minerals from waste material.

concentric fold

See: parallel fold; similar fold.

concentric mine cable

See: portable concentric mine cable.

concentric pattern

Diamonds set in bit face in concentric circles so that a slight uncut ridge of rock is left between stones set in adjacent circles. CF: eccentric pattern.

concentric weathering

See: spheroidal weathering.


See: concession system.

concession system

Under this system the state or the private owner has the right to grant concessions or leases to mine operators at discretion and subject to certain general restrictions. It had its origin in the ancient regalian doctrine that all mineral wealth was the prerogative of the crown or the feudatory lord and applies in almost every mining country in the world, except the United States. Syn: concession. CF: claim system. See also: take.


A bowl-shaped body of limonite or goethite growing in an inverted position on mineralized bedrock and resembling the shell of an oyster or clam coated with a rusty deposit. It is roughly oval or circular in plan, with a smooth or irregular and scalloped outline; it ranges from 2.5 cm to 1 m in diameter and from 2 to 7.5 cm in height.


Said of a type of mineral or rock fracture that gives a smoothly curved surface. It is a characteristic habit of quartz and of obsidian. Etymol: like the curve of a conch (seashell).

conchoidal fracture

A fracture with smooth, curved surfaces, typically slightly concave, showing concentric undulations resembling the lines of growth of a shell. It is well displayed in quartz, obsidian, and flint, and to a lesser extent in anthracite.


a. Said of intrusive igneous bodies, the contacts of which are parallel to the bedding or foliation of the country rock. CF: discordant.

b. Structurally conformable; said of strata displaying parallelism of bedding or structure. The term may be used where a hiatus cannot be recognized, but cannot be dismissed. c. Said of radiometric ages, determined by more than one method, that are in agreement within the analytical precision for the determining methods; or of radiometric ages given by coexisting minerals, determined by the same method, that are in agreement.


An intimate mixture of an aggregate, water, and portland cement, which will harden to a rocklike mass.

concrete caisson sinking

A shaft-sinking method sometimes used through soft ground down to bedrock. It is similar to caisson sinking, except that reinforced concrete rings are used and an airtight working chamber is not adopted.

concrete plug

A thick layer of reinforced concrete placed in the bottom of a shaft after it has been sunk to the desired depth and permanently lined. The plug resists floor lifting and provides a clean, smooth sump.

concrete shaft lining

See: permanent shaft support; shaft wall.

concrete vibrator

Machine that helps the aggregate to consolidate with minimum interstitial porosity. Gives greater strength as less water is incorporated in the mix, and as consolidation is better than with punning.


a. A hard, compact mass or aggregate of mineral matter, normally subspherical, but commonly oblate, disk-shaped, or irregular with odd or fantastic outlines; formed by precipitation from aqueous solution about a nucleus or center, such as a leaf, shell, bone, or fossil, in the pores of a sedimentary or fragmental volcanic rock, and usually of a composition widely different from that of the rock in which it is found and from which it is rather sharply separated. It represents a concentration of some minor constituent of the enclosing rock or of cementing material, such as silica (chert), calcite, dolomite, iron oxide, pyrite, or gypsum, and it ranges in size from a small pelletlike object to a great spheroidal body as much as 3 m in diameter. Most concretions were formed during diagenesis, and many (esp. in limestone and shale) shortly after sediment deposition. CF: nodule.

b. A collective term applied loosely to various primary and secondary mineral segregations of diverse origin, including irregular nodules, spherulites, crystalline aggregates, geodes, septaria, and related bodies. Not recommended usage.


Characterized by, consisting of, or producing concretions; e.g., a concretionary ironstone composed of iron carbonate with clay and calcite, or a zonal concretionary texture (of an ore) characterized by concentric shells of slightly varying properties due to variation during growth.

concretionary and nodular

Minerals, usually monomineralic aggregates, which are found in detached masses, the forms being sometimes spherical, sometimes irregular, e.g., flint.


Shock or sharp airwaves caused by an explosion or heavy blow.

concussion table

An inclined table, which is agitated by a series of shocks, while operating like a buddle. It may be made self-discharging and continuous by substituting for the table an endless rubber cloth, which is slowly moving against the current of water, as in the Frue vanner. Also called a percussion table.


The process by which a vapor becomes a liquid or solid; the opposite of evaporation.


a. An apparatus used for condensing vapors obtained during distillation; it consists of a condenser tube, either freely exposed to air or contained in a jacket in which water circulates.

b. An accumulator of electrical energy. Also called capacitor.

condenser-discharge blasting machine

A blasting machine that uses batteries or magnets to energize one or more condensers (capacitors) whose stored energy is released into a blasting circuit, to initiate detonators.

condenser maker

In ore dressing, smelting, and refining, one who operates an automatic machine in which fireclay condensers are made.

condenser operator

In ore dressing, smelting, and refining, one who recovers magnesium particles from dust-bearing gas, using shock-chilling condensers and other dust-collecting apparatus. Also called dust operator.

condensing lens

A lens for producing convergent light.


See: waste.

conditioned sinter

A name given to sinter with lime additions.


An apparatus in which conditioning takes place.


Those substances added to the pulp to selectively treat coal or waste surfaces prior to flotation.


Stage of froth-flotation process in which the surfaces of the coal or associated impurities present in a pulp are treated with appropriate chemicals to influence their reaction when the pulp is aerated.

condition the hole

To circulate a higher-than-normal volume of drill fluid while slowly rotating and lowering the drill string from a point a few feet above the bottom to the bottom of the borehole to wash away obstructing materials before resuming coring operations.


The quantity of heat transmitted per unit time from a unit of surface to an opposite unit of surface of material under a unit temperature differential between the surfaces.


a. Guides of rope or of rigid construction to guide the cages or skips in the shaft.

b. A relatively short length of pipe driven through the unconsolidated zone of top soil as the first step in collaring a borehole. Also called stand pipe. c. See: brakeman. CF: surface string.

conductor-cable locomotive

An electric locomotive having a cable on a reel and connected both with the locomotive motor and the trolley wire in the entry, so that the locomotive may be driven into an unwired room.


a. An airway.

b. Pipe or casing placed in a borehole. See also: casing; drivepipe.

conduit hole

A flat or nearly horizontal hole drilled for blasting a thin piece in the bottom of a level.


a. A conical hill or mountain, as an alluvial cone or a volcanic cone.

b. A device used on top of blast furnaces to enable charge to be put in without permitting gas to escape. Syn: bell. c. The conical part of a gas flame next to the orifice of the tip. d. The conical hill or conical mountain built by an active volcano. Explosive volcanoes build their cones from debris, ranging in size from dust to huge blocks, thrown out from the vent and have steep slopes approaching or exceeding the angle of repose. Quieter volcanoes that pour out lava have much gentler slopes. e. A three-sided pyramid made of unfired ceramic materials whose composition is such that when heated at a controlled rate they will deform and fuse at a known temperature. It is placed inside a kiln or furnace with ceramic ware to indicate the temperature of the kiln and the fired condition of the ware. See also: pyrometric cone. f. A solid with a circle for a base and with a convex surface that tapers uniformly to a vertex. g. Geometric pattern of the rock plug or stickup left in the bottom of a borehole drilled by a concave bit. h. Beveled coupling device on a small diamond drill or percussion rock drill used to attach it to a drill column.

cone classifier

a. A cone-shaped hydraulic or free-settling classifier.

b. A conical sheet-steel vessel--usually a 60 degrees cone with its point at the bottom--through which water, clear or weighted, flows upward. Ore, coal, or other mineral matter is fed in at the top. The current carries the smaller particles or those of lowest specific gravity over the rim while the others settle. See also: Callow cone; Caldecott cone; Allen cone; Menzies cone separator; Jeffrey-Robinson cone. Syn: Chance cone; cone system.

cone crusher

A machine for reducing the size of materials by means of a truncated cone revolving on its vertical axis within an outer chamber, the anular space between the outer chamber and cone being tapered. See also: gyratory breaker.

cone cut

A cut in which a number of central holes are drilled toward a focal point and, when fired, break out a conical section of strata.

cone-face bit

See: concave bit.

cone-in-cone structure

a. A secondary structure occurring in marls, limestones, ironstones, coals, etc. It is a succession of small cones of approx. the same size one within another and sharing a common axis.

b. Coal exhibiting a peculiar fibrous structure passing into a singular toothed arrangement of the particles is called cone-in-cone coal or crystallized coal. Syn: crystallized coal.


Upper Middle Pennsylvanian.

cone of depression

The depression, approx. conical in shape, that is produced in a water table or in the piezometric surface by pumping or artesian flow. The shape of the depression is because of the fact that the water must flow through progressively smaller cross sections as it nears the well, and hence the hydraulic gradient must be steeper. See also: water table.

cone penetration test

A soil penetration test in which a steel cone of standard shape and size is pushed into the soil and the force required to advance the cone at a predetermined, usually slow and constant rate, or for a specified distance, or in some designs the penetration resulting from various loads, is recorded.

cone penetrator

A 30 degrees to 60 degrees cone having a basal diameter approx. the same size as an a-size diamond-drill rod used to determine the force required to thrust the cone downward into silty or fine to medium-coarse sands, and hence to obtain information that a foundation or soils engineer may use to calculate some of the load-bearing capabilities of such formations. Syn: cone penetrometer. See also: deflection dial.

cone penetrometer

A cone penetrator equipped with a device that will register the pressure required to drive the cone downward into the formation being tested. Syn: cone penetrator; penetrometer.

cone rock bit

A rotary drill, with two hardened knurled cones that cut the rock as they roll. Syn: roller bit.

cone settler

Conical vessel fed centrally with fine ore pulp. "Undersize" is discharged through a flexible pipe (gooseneck), which permits variation of hydrostatic pressure. This apex discharge is thick and carries the larger sized particles. The peripheral top overflow is thin and carries the finer fraction of the solids.

cone sheet

A curved dike or sheet that is part of a concentric set of such forms that dip inward.

cone system

A method of separating impurities from coal in a metallic cone containing a mixture of sand and water with a specific gravity higher than that of coal and lower than the impurities. The coal floats, and the impurities sink. See also: cone classifier.


Upper Upper Devonian.

confined detonation velocity

The detonation velocity of an explosive or blasting agent under confinement, such as in a borehole.

confined groundwater

Artesian water.

confined space

An enclosed space that has the following characteristics: its primary function is something other than human occupancy; it has restricted entry and exit; and it may contain potential or known hazards. Examples of confined spaces include, but are not limited to, tanks, silos, vessels, pits, sewers, pipelines, tank cars, boilers, septic tanks, and utility vaults. Tanks and other structures under construction may not be considered confined spaces until completely closed. Restricted entry and exit means physical impediment of the body, e.g., use of the hands or contortion of the body to enter into or exit from the confined space.

confining bed

a. A watertight bed above or below a stratum containing artesian water.

b. An impervious stratum above and/or below an aquifier. c. A body of impermeable or distinctly less permeable material stratigraphically adjacent to one or more aquifers. CF: aquitard; aquifuge; aquiclude.


Said of a stream, glacier, vein, or other geologic feature that combines or meets with another like feature to form one stream, glacier, vein, etc.


The quality, state, or condition of being conformable, such as the relationship of conformable strata.


Successive beds or strata are conformable when they lie one upon another in unbroken and parallel order and no disturbance or denudation took place at the locality while they were being deposited. If one set of beds rests upon the eroded or the upturned edges of another, showing a change of conditions or a break between the formations of the two sets of rocks, they are unconformable. CF: unconformable.

conformal map projection

mapped is preserved unchanged.


A term used in Chile for coba with a high salt content. See also: coba.

congelation temperature

a. The freezing point.

b. The temperature at which an oil becomes a solid or is reduced to a standard pasty state.


A coarse-grained clastic sedimentary rock, composed of rounded to subangular fragments larger than 2 mm in diameter (granules, pebbles, cobbles, boulders) set in a fine-grained matrix of sand or silt, and commonly cemented by calcium carbonate, iron oxide, silica, or hardened clay; the consolidated equivalent of gravel. The rock or mineral fragments may be of varied composition and range widely in size, and are usually rounded and smoothed from transportation by water or from wave action. CF: breccia. Syn: puddingstone.

conglomerate mudstone

See: paraconglomerate.


A conglomerate that has reached the same state of induration as a quartzite.

congo bort

Congos used industrially as bort. See also: bort.

congo diamond

See: congos.

congo rounds

Spherical- or near-spherical-shaped congos. See also: congos.


a. Originally and commonly used as a name for a variety of diamonds found in the Republic of the Congo diamond district in Africa and more recently as a descriptive term applied to all diamonds having the appearance and characteristics of those produced in the Republic of the Congo. Congos are white to gray-green and yellow, drusy-surfaced, opaque to somewhat translucent diamonds, having shapes corresponding to the many forms characteristic of the isometric (cubic) crystal system. At one time, congos were considered fit only for use in fragmented form, but a considerable number are now used as tool stone and drill diamonds. Syn: congo diamond. See also: congo rounds; diamond.

b. Sometimes designates drill diamonds ranging from one to eight stones per carat in size.


a. In crystallography, any motif that may generate another by rotation or translation, but with no change in chirality.

b. In phase equilibria, the melting of a crystalline compound to a liquid of the same composition. CF: incongruent melting.

congruent forms

In crystallography, two forms that may each be derived from the other by rotation about an axis of symmetry.

congruent melting

A geologic or metallurgical process in which a binary compound melts at a certain concentration to a liquid of its own composition. CF: incongruent melting.


Cone-shaped. In mineralogy, usually an elongated cone as are most icicles.

conical drum

A winding drum, cone-shaped at each end, for balancing the load upon the engine during winding operations. See also: winding drum. The heavily loaded upgoing rope winds on the small diameter while the lightly loaded downgoing rope winds off the large diameter of the cone.

conical head gyratory crusher

Gyratory-type crusher used for secondary reduction and identified by the shape of its breaking head. The large included angle of the breaking-head surfaces greatly increases the ratio of discharge to feed area; a large ratio permits crushed materials to separate to prevent power-consuming clogging and packing. The crusher's higher gyrating speed and large discharge area make it eminently suitable for fine crushing at a high capacity.

conical mill

See: Hardinge mill.

conical refraction

The refraction of a ray of light at certain points of double-refracting crystals, so that on emerging from the crystal it widens from an apex into a hollow cone (external conical refraction), or on entering diverges into a cone and issues as a hollow cylinder (internal conical refraction).


An orthorhombic mineral, CaCu(AsO (sub 4) )(OH) ; adelite group; forms series with austinite, with calciovolborthite, and with cobaltoaustinite; formerly called higginsite.


Method of obtaining true sample from a pile of ore by forming a cone with the material flattening the cone, and removing shovelfuls successively onto four separate heaps of which two are rejected. If there is sufficient material the two opposite quadrants are rejected and the remaining two are combined, reconed, and requartered. As the process is repeated and the pile shrinks, it must be crushed to a smaller size to permit accurate blending of the various sized particles during mixing. Syn: upconing; quartering.

coning and quartering

A method of sample reduction. Syn: quartering.

conjugated veins

Two sets of related veins that dip in different directions.

conjugate fault system

A system of two intersecting sets of parallel faults.

conjugate impedance

Two impedances having resistive components that are equal and reactive components that are equal in magnitude but opposite in sign are known as conjugate impedances.

conjugate joint systems

Sets of intersecting joints that are sometimes perpendicular or rectilinear, and often mineralized to form vein systems. Joint patterns such as these are believed to be the result of compressive stresses that were relieved by joint formation rather than the formation of a single fissure.

Conkling magnetic separator

A conveying belt that passes under magnets, below which belts run at right angles to the line of travel of the main belt. The magnetic particles (tramp iron) are lifted up against these crossbelts and are thus removed.

Conklin process

A dense-media coal cleaning process in which the separating medium consists of minus 200-mesh magnetite (sp gr, 5.2) in water in the desired proportions (4.4 parts of water to 1 part of magnetite provides an effective specific gravity of about 1.9). This process has the advantage that the medium requires little agitation to keep it in suspension and is easily removed from the clean coal and refuse.


a. Originating at the same time as adjacent material; esp. pertaining to waters and volatile materials (such as carbon dioxide) entrapped in sediments at the time the deposits were laid down.

b. Said of fluids derived from the same magma.

connate water

Water entrapped in the interstices of a sedimentary rock at the time of its deposition. CF: interstitial water; formation water.

connecting frame

A device similar to a guide frame for shaker conveyors, but with provision for insertion of the puller rod. A connecting frame can be inserted between any two standard trough sections to serve as a substitute for a connecting trough on single-arm electric or air devices.

connecting trough

A shaker conveyor trough of standard length to which special lugs or plates have been attached to provide a means of connecting the trough to the driving arms of the conveyor drive unit. All motion of the conveyor is transmitted through the connecting trough. The term drive trough is frequently used for this special type of trough.

connecting trough support

The means of supporting connecting troughs where they pass over the drive unit. The support is attached to the drive unit frame and is designed to allow the connecting trough freedom of movement in the direction of the panline. Supports may be of the ball frame, wheel, rolled, or rocker arm types.

connecting wire

Wire used to extend the firing line or leg wires in an electric blasting circuit.


A hexagonal mineral, Cu (sub 19) Cl (sub 4) (SO (sub 4) )(OH) (sub 32) .3H (sub 2) O ; having SO (sub 4) replaced by NO (sub 3) toward buttgenbachkite; deep blue; formerly known as footeite.


Isothermal construction line between two equilibrated phases. See also: tie line.


A polarizing microscope using convergent light with the Bertrand lens inserted, used to test the interference figures of crystals. CF: orthoscope.

Conrad counterflush coring system

A system, the notable feature of which is the provision of a reversed mud flush circulation that permits uninterrupted core recovery in the rotary system of drilling.

Conrad machine

Mechanized pit digger used in checking of alluvial boring. Five-foot-long (1.52-m-long) sections of tubing 24 in (61 cm) in internal diameter are worked into the ground from their mounting on a tractor, the spoil being at the same time removed by means of a bucket or grab. In suitable ground 50 ft (15.2 m) or more depth has been reached.


a. Said of a natural group of sediments or sedimentary rocks related to one another by origin; e.g., a consanguineous association (such as flysch, molasse, or paralic sediments) interrelated by common ancestry, environment, and evolution. Syn: consanguinity.

b. See: comagmatic.

consanguineous association

Natural group of sediments or of rocks of related origin.


The genetic relationship that exists between igneous rocks that are presumably derived from the same parent magma. Such rocks are closely associated in space and time and commonly have similar geologic occurrence and chemical and mineralogic characteristics. Adj. consanguineous. See also: comagmatic.


A syn. of sutured, preferred in European usage, but obsolescent in American usage.


Conserving, preserving, guarding, or protecting; keeping in a safe or entire state; using in an effective manner or holding for necessary uses, as mineral resources.

conservative properties

Those properties of the ocean, such as salinity, the concentrations of which are not affected by the presence or activity of living organisms, but which are affected only by diffusion and advection.

conset jig

Jig developed for Mesabi iron ores in which vertical movement of water is produced by low-pressure inflation and deflation of rubber tubes just below screens. See also: jig.


a. The degree of solidity or fluidity of bituminous materials.

b. The relative ease with which a soil can be deformed. c. A property of a material determined by the complete flow force relation. d. The properties of a slip that control its draining, flowing, and spraying behavior. e. Percentage of solids in pulp. f. Fluidity.

consistency limits

The liquid limit, plastic limit, and shrinkage limit. These all apply to the water content of a clay, each in a certain state as defined by British Standard 1377. See also: Atterberg limits.

consolidated deposits

In geology, any or all of the processes whereby loose, soft, or liquid earth materials become firm and coherent.

consolidated sediment

A sediment that has been converted into rock by compaction, deposition of cement in pore spaces, or by physical and chemical changes in the constituents.


a. Any process whereby loosely aggregated, soft, or liquid earth materials become firm and coherent rock; specif. the solidification of a magma to form an igneous rock, or the lithification of loose sediments to form a sedimentary rock.

b. The gradual reduction in volume and increase in density of a soil mass in response to increased load or effective compressive stress; e.g., the squeezing of fluids from pore spaces. See also: lithification.

consolidation hole

Borehole into which chemical solutions or grout are injected to cement or consolidate fragmental rock material. CF: grout hole.

consolidation settlement

The gradual settlement of loaded clay.

consolidation test

A test in which an undisturbed sample of clay measuring 6 cm in diameter and 2 cm thick is confined laterally in a metal ring and compressed between two porous plates that are kept saturated with water. A load is applied and the clay consolidates, the excess pore water escaping through the porous stones. After each increment of load is applied, it is allowed to remain on the sample until equilibrium is established, and a consolidation curve showing the deformation with time is obtained for each increment.

consolidation trickling

During closing of bed or particles in the suction half of jigging cycle, interstitial burrowing down of fastest moving small particles before the mass of particles becomes too compact for movement.


A group of copper-nickel alloys containing 45% to 60% copper with minor amounts of iron and manganese, and characterized by relatively constant electrical resistivity irrespective of temperature; used in resistors and thermocouples.

constant error

A systematic error that is the same in both magnitude and sign throughout a given series of observations (the observational conditions remaining unchanged) and that tends to have the same effect upon all the observations of the series or part thereof under consideration; e.g., the index error of a precision instrument.

constant-weight feeder

a. An automatic device that maintains a constant rate of feed of ore from the bin or stockpile to the grinding circuit. It is controlled by tilt due to the weight of ore on a balanced length of the belt conveyor; by electrically vibrated chute; by pusher gear; by timed delivery from automatically loaded hoppers.

b. A feeder intended to deliver a certain weight per unit of time.

constituent of attritus

Constituents are the petrographic entities of the attritus that are recognizable in thin sections only by the microscope. The following constituents may be distinguished in coals: translucent humic degradation matter; brown or semitranslucent matter; opaque matter (granular, massive); resins and resinous matter; spores and pollen; cuticles and cuticular matter; algae and algae matter.

constitutional change

Transformation of a constituent in an alloy; e.g., austenite into pearlite.

constitutional water

Water molecules completely bound into a hydrated crystal, e.g., in gypsum, CaSO (sub 4) .2H (sub 2) O .

constitution diagram

A graphical representation of the temperature and composition limits of phase fields in an alloy system as they actually exist under the specific conditions of heating or cooling (synonymous with phase diagram). A constitution diagram may be an equilibrium diagram, an approximation to an equilibrium diagram, or a representation of metastable conditions or phases. CF: equilibrium diagram.

constructed wetland

A man-made marsh that is designed to be slow-draining so that specific species will flourish, primarily to replace natural wetlands that have been drained and filled prior to development. In mining, some constructed wetlands are designed to fix metals and other contaminants, primarily by the reduction of metal sulfates to sulfides, or the formation of oxides or carbonates. When the term is also applied to systems constructed without plants, they consist of buried substrates through which the contaminated water is passed under low oxygen or reducing conditions.

constructive possession

That possession that the law annexes to the legal title or ownership of property, when there is a right to the immediate actual possession of such property, but no actual possession.

consulting engineer

A specialist employed in an advisory capacity. Normally, this person does not manage or direct any operation, and is at the service of the board rather than of the company's administrative and executive staff.

consulting mining engineer

A highly qualified mining engineer with a wide background of experience in this particular field. The engineer may be asked by a client or company to examine a property and prepare a report and evaluation or to give advice or expert evidence in cases of alleged subsidence damage.

consumable electrode-arc melting

A method of arc melting in which the electrode itself serves to supply the metal; this method is commonly employed for melting titanium and zirconium.


To use up; to expend; to waste; as in the chemical and mechanical loss of mercury in amalgamation.

consumption charge

That portion of a utility charge based on energy actually consumed, as distinguished from the demand charge.


a. A plane or irregular surface between two types or ages of rock.

b. The surface of delimitation between a vein and its wall, or country rock.

contact angle

The angle across the water phase of an air-water-mineral system, used to measure effect of surface conditioning.

contact bed

In geology, a bed lying next to or in contact with a formation of different character.

contact breccia

A breccia around an igneous intrusion, caused by wall-rock fragmentation and consisting of both intrusive material and wall rock; intrusion breccia. CF: agmatite.

contact deposit

A mineral deposit between two unlike rocks. The term is usually applied to an orebody at the contact between a sedimentary rock and an igneous rock. See also: contact vein.

contact erosion valley

A valley that has been eroded along a zone of weakness at the contact between two different kinds of rock, as between two different sedimentary formations, between igneous and sedimentary rocks, along a fault, or along an upturned unconformity.

contact goniometer

A protractor for measuring the angles between adjacent crystal faces. See also: goniometer; reflection goniometer.

contact line

The line of intersection of a contact surface with the surface of an exposure or with the surface of bedrock covered by mantle rock; it may be exposed or concealed.

contact logging

In this type log, provision is made for electrodes to be pressed firmly against the borehole wall. By doing this, current flowing from the electrodes to the wall of the borehole no longer has to traverse the mud. The path from the electrodes through the mud filter cake that sheaths permeable beds is also reduced to a mininium. The electrode spacing of contact logging devices is very small by comparison with the spacings used in conventional logging devices. Consequently, contact logging devices see very much more detail in the beds they pass through.

contact logging device

A device that consists of a spring bow very analogous to a section gage. On one arm of the bow is a rubber pad shaped to fit the curvature of the hole. In this pad, slightly recessed, are three electrodes of about diameter 1/2 in (1.3 cm) and located at 1-in (2.54-cm) intervals. These three electrodes are used to record two resistivity curves. One curve is a three-electrode type with a spacing of 1-1/2 in (3.8 cm), and the second is a two-electrode type with a spacing of 2 in.


Adj. of contact metamorphism.

contact metamorphic

Applied to rocks and/or minerals that have originated through the process of contact metamorphism.

contact metamorphism

A process taking place in rocks at or near their contact with a body of igneous rock. Metamorphic changes are effected by the heat and materials emanating from the magma and by some deformation connected with the emplacement of the igneous mass. CF: thermal metamorphism; metamorphic aureole. Approx. syn: pyrometasomatism. Adj: contact-metamorphic. See also: exomorphism; endomorphism.

contact-metasomatic deposit

A deposit formed by high-temperature magmatic emanations along an igneous contact.

contact metasomatism

A mass change in the composition of rocks in contact with an invading magma, from which fluid constituents are carried out to combine with some of the country-rock constituents to form a new suite of minerals.

contact mineral

A mineral formed by contact metamorphism.

contact process

A process for making sulfuric acid. Sulfur dioxide gas (obtained by burning pyrite) is purified by electrical precipitation, and is passed over a catalytic agent to form sulfur trioxide that combined with water produces sulfuric acid.

contact reef

S. Afr. This term generally denotes the Ventersdorp contact reef, a gold-bearing conglomerate beneath the Ventersdorp lavas and frequently overlying mineralized horizons of the Witwatersrand system.

contact resistance

The resistance observed between a grounded electrode and the ground, or between an electrode and a rock specimen.

contact rocks

Rocks produced by contact metasomatism. They include both the border rocks of the intrusion and metamorphosed or recrystallized portions of the intruded rocks, esp. limestone. See also: skarn; tactite.

contact shoe

Collector shoe, which maintains contact between the conducting wire or rail and the electric vehicle being powered.

contact twin

a. The simplest type of twin, in which two portions of a crystal appear to have been united along a common plane after one portion has been rotated 180 degrees relative to the other portion. The plane of contact (plane of union or the composition face) may or may not be the twinning plane. Syn: juxtaposition twin.

b. A twinned crystal wherein the individual twins meet at a surface. CF: interpenetration twin; penetration twin.

contact vein

A contact deposit in vein form. See also: contact deposit.

contact zone

See: aureole.

container winding

This winding system makes use of a coal receptacle on small rollers that fits closely in the cage. During the previous wind, it is filled near the shaft, and similarly it is emptied very quickly at the surface and returned to the pit bottom on the next wind.


a. See: impurity.

b. A harmful, irritating, or nuisance airborne material.


Process whereby the chemical composition of a magma is altered as a result of the assimilation of inclusions or country rock. See also: hybridization; dilution.


The situation when the price of a metal for forward or future delivery is greater than the cash or spot price of the metal. Contangos occur when the metal is in plentiful supply. The size of the contango does not normally exceed the cost of financing, insuring, and storing the metal over the future delivery period.


Formed or existing at the same time. Said of lava flows interbedded in a single time-stratigraphic unit, and generally of any feature or facies that develops during the formation of the enclosing rocks.

contemporaneous deformation

Deformation that takes place in sediments during or immediately following their deposition. Includes many varieties of soft-sediment deformation, such as small-scale slumps, crumpling and brecciation, but in some areas features of large dimensions.


Adjoining, touching, or connected throughout, as in a group of mining claims.

contiguous claims

Mining claims that have a side or end line in common.

contiguous limonite

Limonite in the gangue around and adjoining a cavity or a group of cavities formerly occupied by iron-bearing sulfide.

continental alluvium

Alluvium produced by the erosion of a highland area and deposited by a network of rivers to form an extensive plain.

continental basin

A closed structural depression of regional extent in the interior of a continent.

continental deposit

A sedimentary deposit laid down on land or in bodies of water not directly connected with the ocean, as opposed to a marine deposit; a glacial, fluvial, lacustrine, or eolian deposit formed in a nonmarine environment. See also: terrestrial deposit. Syn: continental sediment.

continental gland-type capping

A wire-rope capping method in which a rope-clamping device is used instead of a capping. The end of the rope is turned back upon itself over grooved block with a suitable radius, and the short end of the rope is clamped on to the main rope above the block.

continental margin

a. The zone separating the emergent continents from the deep sea bottom. It generally consists of the continental shelf, the continental slope, and the continental rise.

b. The submerged prolongation of the land mass of the coastal state, consisting of the seabed and subsoil of the shelf, the slope, and the rise.

continental nucleus

See: shield.

continental plate

Lithosphere underlying a continent that is part of a tectonic plate.

continental platform

The platformlike mass of a continent that stands above the surrounding oceanic basins. Syn. for continental shelf.

continental rise

The submarine surface beyond the base of the continental slope, generally having a gradient of less than 1:1,000, occurring at depths from 4,500 to 17,000 ft (1.37 to 5.18 km), and leading down to abyssal plains.

continental sediment

See: continental deposit.

continental shelf

a. The gently sloping tread around a continent, extending from the low-water line to the depth of approx. 100 fathoms (183 m), at which depth there is a marked increase of slope toward the great depths.

b. The gently sloping, shallowly submerged marginal zone of the continents extending from the shore to an abrupt increase in bottom inclination. The greatest average depth is less than 60 ft (18.3 m), and the width ranges from very narrow to more than 200 mi (322 km). c. An area of a coastal State comprising the seabed and subsoil of the submarine areas that extend beyond its territorial sea throughout the natural prolongation of its land territory to the outer edge of the continental margin, or to a distance of 200 nmi (370 km) from the baselines from which the breadth of the territorial sea is measured where the outer edge of the continental shelf does not extend up to that distance. See also: outer continental shelf.

continental shield

See: shield.

continental slope

a. The declivity from the offshore border of the continental shelf at depths of approx. 100 fathoms (600 ft or 183 m) to oceanic depths. It is characterized by a marked increase in gradient.

b. Continuously sloping portion of the continental margin with gradient of more than 1:40, beginning at the outer edge of the continental shelf and bounded on the outside by a rather abrupt decrease in slope where the continental rise begins at depths ranging from about 4,500 to 10,000 ft (1.4 to 3.0 km). Formerly considered to extend to the abyssal plains.

continental terrace

The sediment and rock mass underlying the coastal plain, the continental shelf, and the continental slope.


The concept that where there is no change of state, seawater is incompressible and the liquid matter is neither created nor destroyed. If there is any vertical contraction in a volume of fluid, therefore, there must be a horizontal expansion, so that the original volume is maintained. This is accomplished by motion resulting in changes of the shape of the original parcel of water.

continuous azimuth method

A method of traversing by which the azimuth of the survey lines is obtained from the instrument.

continuous-bucket elevator

This type of elevator has the buckets so shaped and attached to the chain or belt that the back of each serves as a discharge chute for the one immediately succeeding it. Syn: bucket elevator.

continuous-bucket excavator

An excavator consisting of a series of buckets attached to a continuous chain, guided by two or more ladders. The buckets are drawn against the bank face, taking a cut of constant depth, while simultaneously the machine moves slowly along the ground on a bench above or below the bank; often used in opencast mining in soft deposits.

continuous casting

A casting technique in which an ingot, billet, tube, or other shape is continuously solidified while it is being poured, so that its length is not determined by mold dimensions.

continuous charge

A charge of explosive that occupies the entire drill hole, except for the space at the top required for stemming.

continuous coal cutter

A coal mining machine of the type that cuts the face of the coal without being withdrawn from the cut.

continuous coring

A borehole-drilling technique whereby the cuttings-removal agent is countercirculated through an inside flush-coupled-type drill string to deliver both the cuttings and core produced to a tray or container at the surface.

continuous cutters

Coal-cutting machines such as the shortwall cutter, longwall cutter, and overcutting machines. They are known as continuous cutters because a continuous cut can be made the full width of the face without stopping these machines, while machines of the intermittent variety must be frequently reset.

continuous deformation

Deformation accomplished by flowage of rocks rather than by rupture.

continuous drier

A drier in which the wet material moves through the drying cycle in an uninterrupted flow pattern in contrast to a batch drier.

continuous driving

In this operation, the same personnel do the drilling, blasting, and mucking while working continuously round after round. They can in this way--except for the time for ventilation--be at work during the whole shift. Continuous driving is used when the advance per round is low and the mucking or the drilling and blasting do not need more than a part of the shift.

continuous extraction

Extraction (leaching) of solids by liquid that cycles continuously countercurrent to the material it is depleting of the sought value (e.g., gold in cyanide process), the pregnant liquid at a certain stage being stripped of value and returned as barren solution.

continuous filter

See: Oliver filter.

continuous-flight auger

A drill rod with continuous helical fluting, which acts as a screw conveyor to remove cuttings produced by an auger drill head. Also called auger.

continuous flow respirator

An atmosphere-supplying respirator that provides a continuous flow of respirable gas to the respiratory inlet covering.

continuous furnace

Said of a process in which the charge enters at one end, moves through continuously, and is discharged at the other end. Syn: furnace.

continuous haulage

A process that is designed to move the mined product (usually coal) from a continuous mining machine to a mine belt conveyor system as a continuous flow. One end of the continuous haulage system (the outby end) always remains positioned so that it discharges onto the mine belt; the other end (inby end) is free to move as the mining machine advances so as to be able to receive the product from the machine's conveyor discharge.

continuous mill

A rolling mill consisting of a number of stands of synchronized rolls (in tandem) in which metal undergoes successive reductions as it passes through the various stands.

continuous miner

A mining machine designed to remove coal from the face and to load that coal into cars or conveyors without the use of cutting machines, drills, or explosives. See also: Goodman miner; Marietta miner.

continuous mining

Mining in which the continuous mining machine cuts or rips coal from the face and loads it onto conveyors or into shuttle cars in a continuous operation. Thus, the drilling and shooting operations are eliminated, along with the necessity for working several headings in order to have available a heading in which loading can be in progress at all times. See also: conventional machine mining; plow-type machine.

continuous profiling

A seismic method of shooting in which seismometer stations are placed uniformly along the length of a line and shot from holes also spaced along the line so that each hole records seismic-ray paths identical geometrically with those from immediately adjacent holes, so that events may be carried continuously by equal-time comparisons. CF: correlation shooting.

continuous reaction series

A reaction series in which early-formed crystals in a magma react with later liquids without abrupt phase changes; e.g., the plagioclase feldspars form a continuous reaction series. CF: discontinuous reaction series.

continuous recording

In geophysics, the process of making uninterrupted records or observations over selected periods of time.

continuous ropeway

An aerial ropeway that operates on the same principle as the endless rope haulage. The loaded buckets are hauled by an endless rope in one direction and the empty buckets travel back on the return rope alongside.

continuous sampling

Taking a sample from each unit so that increments are taken at regular intervals whenever the coal or coke is handled at the point of sampling.

continuous sintering

Presintering, or sintering, in such manner that the objects are advanced through the furnace at a fixed rate by manual or mechanical means. Syn: stoking.

continuous smelter

Any smelter that is fed constantly and that discharges frit in a continuous stream. The passage of the material through the smelter is generally effected by gravitational flow.

continuous spectrum

a. The band of all wavelengths in the electromagnetic spectrum (the rainbow colors, red, orange, yellow, green, blue, and violet), merging one into the other, produced by all incandescent solids.

b. The spectrum of a wave, the components of which are continuously distributed over a frequency range.

continuous stream conveyor

See: en masse conveyor.

continuous vertical retort

A type of gas retort in which coal is continuously charged into the top of the retort, coke is extracted from the bottom, and town gas is drawn off. Continuous vertical retorts are also used in the zinc industry. The charge of briquetted coke and roasted concentrate is continuously added through the top and zinc vapor is drawn off and condensed.


a. The intricate folding, bending, or twisting-together of laminated sediments on a considerable scale, the laminae being drawn out or compressed in such a manner as to suggest kneading more than simple folding; esp. intraformational contortion. Also, the state of being contorted.

b. A structure produced by contortion.


a. An imaginary line, or a line on a map or chart, that connects points of equal value, e.g., elevation of the land surface above or below some reference value or datum plane, generally sea level. Contours are commonly used to depict topographic or structural surfaces; they can also readily show the laterally variable properties of sediments or any other phenomenon that can be quantified. CF: structure contour. Syn: contour line.

b. The outline or configuration of a surface feature seen two-dimensionally, e.g., the contour of a mountain pass or a coastline. c. A line drawn through points of equal elevation on any surface. It is the intersection of a horizontal plane with the surface. d. A line or a surface at all points of which a certain quantity, otherwise variable, has the same value (as lines of equal elevation on the ground or isothermal surfaces in a heat-conducting solid). e. As a verb, to construct (as a road) in conformity to a contour. To provide (as a map) with contours (contour lines). To draw or to plot a contour. f. The profile or cross-sectional outline of a bit face.

contour diagram

a. A type of petrofabric diagram prepared by the contouring of a point diagram. Its purpose is to obtain easier visualization of the results of the petrofabric study.

b. An equal-area projection of structural data in which the poles have been contoured according to their density per unit area on the projection.

contour gradient

A line marked on the ground surface at a given constant slope.

contour mining

Surface mining that progresses in a narrow zone following the outcrop of a coal seam in mountainous terrain, and the overburden, removed to gain access to the mineral commodity, is immediately placed in the previously mined area, such that reclamation is carried out contemporaneously with extraction.

contour plan

A plan drawn to a suitable scale showing surface contours or calculated contours of coal seams to be developed. These plans are important during the planning stage of a project. See also: interpolation of contours.

contour race

A watercourse following the contour of the country.


In coal mining, a term meaning cigars, cigarettes, pipes, and other contrivances for smoking, matches, and mechanical lighters. It is a violation of safety regulations to take contraband below ground or to have contraband in one's possession below ground.


a. A bargain or agreement voluntarily made upon good consideration, between two or more persons capable of contracting to do, or forbearing to do, some lawful act.

b. In mining, applies to an agreement between operator and worker to pay the latter so much per foot for excavating drift or stope. These people are known as contract miners and are usually skilled workers. They work harder than people on wages due to the incentive of higher earnings. c. Agreement between contractor and employing company to construct, erect, install, and operate specified works under agreed conditions. A cost-plus contract is one in which the contractor undertakes a comprehensive activity, part of which may be subcontracted (or let out). A unit contract is one in which company awards a restricted part of the job to the contractor. See also: agreement.

contraction cavities

The bulk of the contraction that accompanies the solidification of metals is concentrated in the feeder heads and risers, from which molten metal flows to compensate for contraction in the casting of ingot proper.

contraction vein

A vein formed by the filling of a fissure caused by contraction resulting from the drying or cooling of the surrounding rock.

contract loader

In bituminous coal mining, one who is paid a certain rate per ton of car of coal mined, and employs one or more loaders whom the loader pays out of personal earnings.

contract miner

a. In anthracite and bituminous coal mining, one who operates electric or compressed-air machines to drill holes into the working face of coal or rock for blasting, and shovels coal into cars after blasting. A contract miner is usually engaged in production work, i.e., the mining of coal only, and is paid on a tonnage basis. In anthracite regions, the miner is paid the wage rate of a consideration mine when encountering obstructions of rock or slate that prevent earning an amount in excess of a fixed or specified rate per day. Also called contract driller; contract drilling-machine operator; contract contractor.

b. In metal mining, one who drills, blasts, and loads ore or rock into cars in a mine. Is usually engaged in production work, i.e., the mining of ore only, and is paid on a contract basis (so much per ton, cubic yard, or cars of ore produced).


a. The person who signs a contract to do certain specified work at a certain rate of payment. In mining, the contractor is an experienced miner or hard-heading miner. He or she employs other people and the work may proceed on a three-shift basis.

b. S. Afr. Mine worker undertaking special tasks on a contractual basis such as shaft sinking, development blasting, etc.

contract person

See: contract miner.

contract work

Work that is outside the scope of the mine price list and is performed on the basis of an agreement between a miner and the mine manager. The agreement may be only verbal and renewable weekly or monthly. Payment is made according to performance. In development work, the contract rate is usually per yard advance. There may be bonus payments for good work or for extra performance. See also: piecework.


Stream aggradation caused by an obstruction. Syn: dam gradation.

contra-rotating axial fan

A modification of the axial-flow fan. It consists of two impellers with aerofoil shaped blades that rotate in opposite directions. The drive is by means of a single motor through differential gears, or two separate motors, one for each impeller. They are placed in the airstream and act as streamlined hubs. These fans are available for auxiliary ventilation in mines. See also: axial-flow fan.

contributory negligence

In mining, means that the law imposes upon every person the duty of using ordinary care for his or her own protection against injury. It is not synonymous with assumption of risk.


a. The dimensional data used to establish the position, elevations, scale, and orientation of the detail of a map and that are responsible for the interpretations placed on a map.

b. A section or reach of an open channel in which natural or artificial conditions make the water level above it a stable index of discharge. It may be either complete (i.e., water-surface elevation above the control is completely independent of downstream water-level fluctuations) or partial; it may also shift. c. That waterway cross section that is the bottleneck for a given flow and determines the energy head required to produce the flow. In an open channel, it is the point at which flow is at critical depth; in a closed conduit, it is the point at which hydrostatic pressure and cross-sectional area of flow are definitely fixed, except where the flow is limited at some other point by a hydrostatic pressure equal to the greatest vacuum that can be maintained unbroken at that point. d. Any of the factors determining the nature of geologic formations at a given place. e. In geology, the background and the quantity of data that are responsible for the interpretation placed on a map or a cross section. f. An attempt to guide a borehole to follow a predetermined course through the use of wedges or by manipulation of the drill string.

control assay

An assay made by an umpire to determine the basis on which a purchaser is to pay the seller for ore. See also: umpire.

control chart

Graph showing, horizontally, the operating norm and also the upper and lower control limits within which deviations must be held. Should these values exceed the permitted variance, special steps must be taken to locate and correct the upsetting factor or factors.

controlled blasting

Techniques used to control overbreak and produce a competent final excavation wall. See also: line drilling; smooth blasting; cushion blasting. Syn: presplitting.

controlled caving

A mining method utilizing the advantages of longwalls, but at the same time without filling. In this method, the working room in front of the working face is protected by close lines of props and cribs, which are portable and easily taken to pieces. As the face proceeds, the cribs are shifted as well as the props with the face, leaving the mined-out room to cave. This method is also called mining with self-filling.

controlled cooling

Cooling from an elevated temperature in a predetermined manner to avoid hardening, cracking, or internal damage, or to produce a desired microstructure. This cooling usually follows a hot-forming operation.

controlled footage

The specified maximum number of feet of borehole a single diamond- or other-type bit may be allowed to drill in a specific-type rock, as predetermined by the drill supervisor.

controlled gravity conveyor

See: controlled velocity roller conveyor.

controlled mosaic

A mosaic in which aerial photographs or images have been adjusted, oriented, and scaled to horizontal ground control to provide an accurate representation with respect to distances and distortions. It is usually assembled from photographs that have been corrected for tilt and for variations in flight altitude. See also: mosaic.

controlled release

A paradigm of mine waste management (based upon the eventual oxidation of exposed sulfidic rock and mine wastes) that states that a slow release of contamination over time may be superior to complete containment.

controlled splitting

When airways are arranged in parallel and a prescribed quantity of air is made to flow through each branch. CF: natural splitting.

controlled velocity roller conveyor

A roller conveyor having means to control the velocity of the objects being conveyed. Syn: controlled gravity conveyor. See also: roller conveyor.


Any mechanical or electrical device that is part of or added to a machine or device for automatic regulation or control.

controlling rate

That at which the key machine in a series arranged for continuous ore processing is set to work. The control function may be for quantity passing per time, ratio of size reduction from feed to discharge, or for a necessary physical or chemical change of state of solid or liquid phase of the process.

controlling system

In flotation, that portion of an automatic feedback control system that compares functions of a controlled variable and a command and adjusts a manipulated variable as a function of the difference. It includes the reference input elements, summing point, forward and final controlling elements, and feedback elements.

control man

Person who maintains depth and composition of cryolite bath in aluminum reduction pots within limits favorable to efficient aluminum production.

control on fracture

In quarrying, control on fracture is based on the experimental determination of the type and the grade of explosive, the loading ratio, and the pattern of boreholes.

control point

Any station in a horizontal and/or vertical control system that is identified on a photograph and used for correlating the data shown on that photograph.

control samples

In any continuous process, samples taken often enough (whether by hand or mechanically) so that the operation process may be guided by the samples and weights of the materials involved.


a. A process of mass movement of portions of any fluid medium (liquid or gas) in a gravitational field as a consequence of different temperatures in the medium and hence different densities. The process thus moves both the medium and the heat, and the term convection is used to signify either or both.

b. In hydrothermal systems, the flow of water around and through heated zones adjacent to plutons in response to thermal gradients and controlled by porosity-permeability, salinity, fluid viscosity, and allied factors. The flow is generally down along the periphery, toward the system at depth, and upward along and through its central portions, possibly completing more than one loop.

convection current

a. A thermally produced fluid flow.

b. A closed circulation of material sometimes developed during convection. Convection currents normally develop in pairs; each pair is called a convection cell.

conventional machine mining

A system of mining established for many years in British coal mines. The longwall face is undercut, blasted, and loaded by hand to a face conveyor. The conveyor is then moved forward ready for the next day, the packs are built and the back props withdrawn. Such faces still produce about 60% of the total output and is known as conventional machine mining. It has the disadvantage that there are limits to production because it is cyclic mining, e.g., it involves separate operations as enumerated above. See also: turnover; continuous mining.

conventional mining

The cycle of operations that includes cutting the coal, drilling the shot holes, charging and shooting the holes, loading the broken coal, and installing roof support. Also known as cyclic mining.

conventional mud

A drilling fluid containing essentially clay and water.


a. The gradual decrease in the vertical distance or interval between two specified rock units or geologic horizons as a result of the thinning of intervening strata; e.g., the reduction in thickness of sedimentary beds (as measured in a given direction and at right angles to the bedding planes), caused by variable rates of deposition or by unconformable relationship.

b. Loss of height when a coal seam is extracted on a longwall face, as the roof lowers and the floor lifts. Convergence is an important factor in thin-seam mining. c. Applied to the diminishing interval between geologic horizons. In some instances, this is due to an unconformable relationship and in other instances to variable rates of deposition. d. The line of demarcation between turbid river water and clear lake water, which denotes a downstream movement of water on the lake bottom and an upstream movement of water at the surface. e. In refraction phenomena, the decreasing of the distance between orthogonals in the direction of wave travel. This denotes an area of increasing wave height and energy concentration. f. In paleontology, resemblance that cannot be attributed to a direct relationship or to genetic affinity. g. In oceanography, an area or zone in which the water sinks slowly downward from the ocean surface.

convergence recorder

An appliance for measuring cha An appliance for measuring changes in vertical height, usually at the coalface. It consists of a telescopic strut set between the roof and floor and carries a pen that records the movement on a clockwork-driven chart. See also: romometer.

convergent light

In optical microscopy, a condensing lens causes light to converge at a point within a sample to display optical interference patterns or to enhance the Becke line.

conversion burners

Fuel-burning devices (usually oil or gas) intended for installation in a wide variety of boilers or furnaces.

conversion factor

A number facilitating statement of units of one system in corresponding values in another system.


A furnace in which air is blown through a bath of molten metal or matte, oxidizing the impurities and maintaining the temperature through the heat produced by the oxidation reaction. Also used in converting copper matte.

converter foreperson

A person who supervises workers engaged in converting copper matte to blister copper and directs activities concerned with charging converter, blowing charge, pouring of slag and copper, casting of blister copper, and removal of castings.

converter plant

A plant that incorporates into its structure an insoluble element from the soil, and later, when the plant decays, returns that element to the soil in a soluble form.

converter skimmer

In ore dressing, smelting, and refining, one who makes blister copper (high-grade crude copper) by oxidizing iron and sulfur impurities in copper matte, using a converter.


The process of removing impurities from molten metal or metallic compounds by blowing air through the liquid. The impurities are changed either to gaseous compounds, which are removed by volatization, or to liquids which are removed as slags.

Convertol process

A German process that cleans the coal and also reduces the moisture content to about 10%. Heavy oil is added to a coal slurry containing 50% to 60% water. On mixing, the coal particles become coated with oil and hence resistant to water, whereas the shale particles remain uncoated and easily wetted. By high-speed centrifuging the coal-oil mixture is retained in the centrifuge while the shale particles pass out with the water. The process is not as efficient as froth flotation.

conveyor airlock

A ventilation stopping or separation door through which a conveyor has to run. It consists of at least two well-built partitions, each with some form of airlock designed to pass the belt and yet to reduce to a minimum the leakage of air and the raising of dust. An airlock chute is sometimes used. See also: box check.

conveyor chain

A chain used in the conveying medium of conveyors.

conveyor creep

The downward slippage of a conveyor on an inclined face. With powered supports, this movement is likely to cause ram damage. Anchor stations are necessary to arrest conveyor creep. See also: stell prop.

conveyor dryer

An appliance in which the coal or ore is moved through a chamber containing hot gases on a perforated plate or a heavy mesh, stainless-steel continuous belt.

conveyor elevator

A conveyor that follows a path, part of which is substantially horizontal or on a slope less than the angle of slide of the material and part of which is substantially vertical or on a slope steeper than the angle of slide.

conveyor emergency switch

A specif. designed cable operated emergency stop switch for use with conveyors or conveying systems that are used with a pull cord running alongside or above the conveyor so that it may be reached from any point along the conveyor. Persons falling against or on top of the conveyor will pull on the cord and deactivate the conveyor movement.

conveyor face

A longwall face on which the coal is loaded direct onto a face conveyor. The coal may be loaded by hand or mechanically. The face conveyor delivers its load of coal into tubs or cars or onto a gate conveyor.

conveyor-feeder operator

See: mill feeder.

conveyor loader

a. Conveyor that at its extremity has a digging head that moves with the conveyor and works its way under the coal, which, by the unequal shaking of the conveyor, is carried back to the car. Also called shaking-conveyor loader.

b. One who loads on a conveyor. See also: loader.

conveyor man

a. Person who sets up and tends chain, belt, or shaker (reciprocating) conveyors to transport coal or metal ore about a tipple at the surface from working the working face in a mine. Also called loading-boom operator.

b. In the quarry industry, a person who tends an endless conveyor belt used to transport rock from the crusher to storage bins. Syn: beltman.

conveyor-operator tripper

See: tripper man.

conveyor shaker type

A conveyor designed to transport material along a line of troughs by means of a reciprocating or shaking motion. See also: shaker conveyor.

conveyor shifter

A member of a team responsible for advancing the face conveyor as the coal is worked away. In many modern layouts, the armored conveyor is pushed forward by hydraulic rams.

conveyor track

The path, parallel to the face, occupied by a longwall conveyor. The track is advanced every turnover. Syn: track.

conveyor-tripper operator

See: tripper man.

conveyor-type feeder

Any conveyor, such as apron, belt, chain, flight, pan, oscillating, screw, or vibrating, adapted for feeder service. See also: apron feeder.