Appendix:Dictionary of Mining, Mineral, and Related Terms/C/5

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a. A ferruginous bauxite from Cliache, Dalmatia, Croatia.

b. Colloidal aluminum hydroxide occurring as one of the constituents of bauxite. Also spelled kliachite. See also: laterite; sporogelite. Syn: alumogel.


a. Wales. Shale that is laminated, splitting easily along the planes of deposition. Also called clift.

b. The strata of rocks above or between coal seams.


a. Obsolete var. of cleft. See: cleft.

b. Dialectal var. of cliff. c. A term used in southern Wales for various kinds of shale, esp. a strong, usually silty, mudstone.


In froth flotation, the prevailing balance of chemical energy reached by the reacting electrical, physical, and chemical forces.


The tendency of an inclined diamond-drill hole to follow an upward-curving, increasingly flat course; also, the tendency of a diamond or other rotary-type bit to drill a hole curved in the updip direction when holes are drilled in alternating hard- and soft-layer rock having bedding planes that cross the borehole at an angle other than 90 degrees to the face of the bit.


One of the internal cracks formed in steel by differential expansion of surface and interior during heating. The tendency for clinks to occur increases with the hardness and mass of the metal, and with the rate of heating.


a. Fused or partly fused coal ash, a byproduct of combustion. CF: core.

b. Coal that has been altered by an igneous intrusion. See also: natural coke. Syn: scoria. c. Partially fused intermediate product in the manufacture of portland cement.


An older term for a feldspathic rock, usually fissile; it is sonorous when stuck with a hammer. Also spelled klinkstone. See also: phonolite.


A prefix to the name of a mineral species or group to indicate monoclinic symmetry as opposed to "ortho" indicating orthorhombic symmetry. See the root mineral name.


a. A group name for amphiboles crystallizing in the monoclinic system.

b. Any monoclinic mineral of the amphibole group; e.g., hornblende, cummingtonite, grunerite, tremolite, actinolite, riebeckite, glaucophane, and arfvedsonite. CF: orthoamphibole.


A collective name for the monoclinic pyroxenes. See also: clinopyroxene.


The inclined crystallographic axis in the monoclinic system, designated a or b in the first setting and a or c in the second. Most mineralogists use the second setting and designate the clinoaxis a.


A monoclinic mineral, 2[(Mg,Fe) (sub 5) Al(Si (sub 3) Al) (sub 4) O (sub 10) (OH) (sub 8) ; chlorite group; occurs in greenschists.


Monoclinic and orthorhombic forms of chrysotile, as determined by X-rays. See also: chrysotile.


A monoclinic mineral, Cu (sub 3) (AsO (sub 4) )(OH) (sub 3) ; formerly called clinoclasite. Syn: aphanesite.


Former name for clinoclase.


An open crystal form of four sides parallel to the clinoaxis a in the monoclinic system. CF: dome; orthodome.


A name for the pyroxene series clinoenstatite and clinohypersthene. CF: enstenite.


A monoclinic mineral, Fe (sub 2) Si (sub 2) O (sub 6) ; pyroxene group; contains up to 15% Mg (sub 2) Si (sub 2) O (sub 6) toward clinohypersthene; dimorphic with ferrosilite.


An instrument for making a borehole survey; i.e., to determine if, and in what direction, a borehole has deviated off the true vertical plane. See also: crooked hole.


a. Cesaro's name for a monoclinic form of guarinite. See also: orthoguarinite.

b. A former name for hiortdahlite.


a. Breithaupt's name for tetrahedrite.

b. A monoclinic mineral, CaZnSiO (sub 4) .H (sub 2) O; forms colorless to white or amethystine clinohedral crystals.


An intermediate member in the series clinoenstatite-clinoferrosilite in the pyroxene group.


Any of various instruments used for measuring angles of slope, elevation, or inclination (esp. the dip of a geologic stratum or the slope of an embankment); e.g., a simple hand-held device consisting of a tube with a cross hair, a graduated vertical arc, and an attached spirit level so mounted that the inclination of the line of sight can be read on the circular scale by centering the level bubble at the instant of observation. A clinometer is usually combined with a compass (e.g., the Brunton compass). Syn: inclinometer; plain clinometer. CF: drift indicator.


An exceptionally accurate instrument for borehole surveying, designed particularly for use with the freezing and cementation methods of shaft sinking; capable of giving the slope of a borehole to within 1 min of arc.


A monoclinic mineral, (Na,K,Ca) (sub 2) Al (sub 3) (Al,Si) (sub 2) Si (sub 13) O (sub 36) .12H (sub 2) O; of the zeolite group.


A group name for monoclinic pyroxenes. Abbrev. cpx. Syn: monopyroxene. CF: orthopyroxene.


A discredited name for phosphosiderite, a dimorph of strengite.


A monoclinic mineral, sodium potassium iron sulfate; possibly dimorphous with ungemachite.


An epidote having the composition of zoisite, Ca (sub 2) Al (sub 3) (SiO (sub 4) ) (sub 3) (OH) ; monoclinic; crystals striated.


a. A monoclinic mineral, Ca(Mg,Al) (sub 3) (Al (sub 3) Si)O (sub 10) (OH) (sub 2) ; mica group. Syn: seyberite; xanthophyllite.

b. A group name for the brittle micas.

Clinton ore

A red, fossiliferous sedimentary iron ore; e.g., the Clinton Formation (Middle Silurian) or correlative rocks of the east-central United States, containing lenticular or oolitic grains of hematite. It supplies the ironworks at Birmingham, AL. See also: fossil ore; flaxseed ore.


Connector between an underground tub, car, truck, or tram, and endless rope haulage. A clip pulley has a broad rim into which studs are set, to grip links of a haulage chain. See also: haulage clip; automatic clip; coupling; clam.

clip method

The clip method of making wire rope attachments is widely used. Drop-forged clips of either the U-bolt or the double-saddle type are recommended. When clips of the correct size are properly applied, the method uses about 80% of the rope strength.


a. Eng. Deposits interstratified with coal; Yorkshire and Midland Counties.

b. A hard earthy clay on the roof of a working place in a coal seam; often a fireclay. c. A miner's term applied to a soft, weak, or loosely consolidated shale (or to a hard, earthy clay), esp. one found in close association with coal or immediately overlying a coal seam. It is so called because it falls away in lumps when worked. An artificially formed aggregate of soil particles. d. A clod of dirt, of greater or less diameter, thin at the edges and increasing in thickness to the middle. See also: kettle bottom. e. An artificially formed aggregate of soil particles.


a. Mid. A short piece of timber about 3 in by 6 in by 24 in (7.6 cm by 15.2 cm by 61.0 cm) fixed between the roof and a prop.

b. A flat wedge over a post. See also: lid. c. To obstruct, hinder, or choke up; e.g., the stoppage of flow through a pipe by an accumulation of foreign matter, or the filling up of the grooves in a file when operating on a soft metal. d. Eng. Rock filling a fault.


Applied to dredges in which the buckets are each connected to the one in front without any intermediate link.

closed circuit

a. A water circuit designed so that the only water added is that necessary to replace the loss of water on the products.

b. A system in which coal passes from comminution to a sorting device that returns oversize for further treatment and releases undersize from the closed circuit.

closed-circuit grinding

A size-reduction process in which the ground material is removed either by screening or by a classifier, the oversize being returned to the grinding unit. Typical examples are a dry pan with screens, dry milling in an air-swept ball mill, and wet milling in a ball mill with a classifier. See also: circulating load.

closed-circuit operation

Retention and retreatment of ore in part of flow a line until it satisfies criteria for release. Used in comminution to reduce overgrinding by passing intermediate particles repeatedly through grinding systems, classifying the product and returning oversize. Used in concentration (e.g., rougher-scavenger-cleaner flotation) to retain a selected fraction of ore in circuit for retreatment (a middling), until it is either upgraded to rank as concentrate or sufficiently denuded of value to be rejected as tailing.

closed-circuit television

System in which television cameras relay pictures of conditions at important points in a plant, thereby aiding workers to watch inaccessible places and exercise extended control.

closed contour

A contour line that forms a closed loop and does not intersect the edge of the map area on which it is drawn; e.g., a depression contour indicating a closed depression, or a normal contour indicating a hilltop.

closed fault

A fault in which the two walls are in contact. CF: open fault.

closed frame

A mine support frame used esp. in inclined shafts where protection from rock pressure is needed on all sides. This completely closed set is provided at the bottom with a sill. The joint is usually effected by tenons, so that when the pressure is exerted in a downward direction the timbers interlock.

closed joint

A joint found in rocks that causes a plane of weakness known variously as a rift or gain. This largely determines the shape of the blocks that may be extracted from a quarry. Also called incipient joint. Syn: gain.

closed-spiral auger

A soil-sampling auger made by spirally twisting a flat steel ribbon to form a tubelike, hollow-center, corkscrewlike device.

closed top

See: cup and cone.

closed traverse

a. A surveying traverse whose accuracy can be checked by the fact that, when it is closed, the angles should add up to 360 degrees , and which ends at its starting point.

b. A surveying traverse that starts and terminates upon the same station or upon a station of known position. CF: open traverse.

closed-water circuit

The separation of solids from a washery slurry so that the water can be returned to the plant and used continuously.

close goods

a. Pure stones, of desirable shapes.

b. Highest class of South African diamonds, as sorted at Kimberly.


Applied to rocks in which the joints are very close together.

close-joints cleavage

See: slip cleavage.

close nipple

A nipple, the length of which is about twice the length of a standard pipe thread and without any shoulder. See also: nipple.

close prospecting

Detailed analysis of a proven placer deposit that should determine: (1) the volumetric measurements of both overburden and gravel; (2) the estimation of the gold or other mineral contents; (3) the average value of the area in pence, cents, carats, or other unit per unit of volume; and (4) all possible information regarding the nature of the overburden and gravel--i.e., whether it is clayey, free wash, etc.--as well as of the bedrock.


Screened or classified between close maximum and minimum limits of size or settlement.

close sheathing

Consists of planks placed side by side along a continuous frame. Its use is to prevent local crumbling of less compacted soils. Since crevices can exist between planks, it should not be used with fine silts or liquid soils, which can seep through these cracks. CF: skeleton sheathing; tight sheathing.

close sizing

a. In screening, choice of sieve sizes that are fairly close in mesh size to restrict size range of each fraction of the material separated.

b. Sizing with screens.

close timbering

The setting of timber sets and lagging very close together when shaft sinking or tunneling through very loose ground or crushed coal in thick seams. See also: cribbing; forepoling.

closing error

When calculating or plotting the distances, angles, or coordinates of a closed traverse or one connecting two accurately located points, the discrepancy between starting and finishing point. This error is adjusted in proportion to the magnitude of the angles and distances involved, if it is below a tolerable limit. See also: error of closure.

closing rope

Operating rope for opening and closing a grab.


Dense, laminated, brownish-red algal coal found in Irkutsk, Russia. It consists of an accumulation of spheroidal algal colonies of different sizes, among which are disseminated great numbers of desmid algae, belonging to the living genus, Closterium.


a. A closed anticlinal structure.

b. The difference in the relative position of the bottom and the collar of a borehole expressed in horizontal distance in a specific compass direction. c. The relative inward movement of the two walls of a stope. d. A cumulative measure of the various individual errors in survey measurements; the amount by which a series of survey measurements fails to yield a theoretical or previously determined value for a survey quantity. e. Used in structural geology, esp. in connection with potential oil structures, to designate the vertical distance between the highest point of an anticlinal structure of an anticlinal structure or fold and the lowest contour that closes around the structure. It is an approximate measure of the capacity of a structural trap for oil and/or gas. f. A portion of brick to close, when required, the end of a course as distinguished from a half brick. See: closure.

closure meter

An instrument for indicating the amount of closure that has taken place. Wall closure in mines is measured by this instrument. Also called sag meter.


A group of ferromagnesian minerals in igneous rock, from a few inches to a foot or more in size, commonly drawn out longitudinally, that may be a segregation or an altered xenolith.


Eng. Brattice constructed of a coarse, specially prepared canvas.


The sintering or semifusion of ores during roasting.

cloud chamber

A device that displays the tracks of charged atomic particles. It is a glass-walled chamber filled with a supersaturated vapor. When charged particles pass through the chamber, they leave a cloudlike track much like the condensation trail of a plane. This track permits scientists to see the paths of these particles and study their motion and interaction. See also: bubble chamber; spark chamber.

clouded agate

Chalcedony with irregular or indistinct patches of color. See also: agate.

cloudy chalcedony

Chalcedony with dark, cloudy spots in a light-gray transparent base.

cloudy stain

In mica, a cloudlike effect that occurs in various colors.


Scot. A mineral related to asphalt, occurring in patches in blue limestone and in blue flags at Inganess, Orkney. It is soluble in benzol and at a red heat gives off a large amount of illuminating gas.


a. A bend in a roadway or passage in a coal seam.

b. A large fall of roof. c. A tough fireclay.

clustered carbide

See: interspersed carbide.


See: botryoid.

cluster mill

A rolling mill in which each of the two working rolls of small diameter is supported by two or more backup rolls.


Strata containing coalbeds, particularly those of the Pennsylvanian Period. Used as a proper name for a stratigraphic unit more or less equivalent to the Pennsylvanian Period. Abbrev. of Coal Measures.

CMI centrifuge

A fine-coal dewatering machine consisting of two rotating elements, an outside conical screen frame, and an inside solid cone, which carries spiral hindrance flights. By a slight difference in the number of teeth in the gears, the screen element moves slightly faster, in the same direction, than the solid cone. Material enters the machine from the top and falls on the solid cone where centrifugal force throws it against the screen. It slides down the screen until it meets the upper end of the hindrance flights, and, in doing so, the water begins to pass through the screen. The flights spiral downward, and, as the screen moves slowly around them in the direction of the downward pitch, the solids gradually find their way to the bottom of the screen basket and the zone of maximum centrifugal force, tending to remove all of the water. See also: dewatering.


a. The binding of individual particles to form flocs or agglomerates and thus increase their rate of settlement in water or other liquid. See also: flocculation.

b. The coalescence of fine particles to form larger particles.


A soluble substance, such as lime, which, when added to a suspension of very fine solid particles in water, causes these particles to adhere in clusters that will settle easily. Used to assist in reclaiming water used in flotation.


A readily combustible rock containing more than 50% by weight and more than 70% by volume of carbonaceous material, including inherent moisture; formed from compaction and induration of variously altered plant remains similar to those in peat. Differences in the kinds of plant materials (type), in degree of metamorphism (rank), and in the range of impurity (grade) are characteristic of coal and are used in classification. Syn: black diamond.

coal analysis

The determination, by chemical methods, of the proportionate amounts of various constituents of coal. Two kinds of coal analyses are ordinarily made: (1) proximate analysis, which divides the coal into moisture (water), volatile matter, fixed carbon, and ash. Percentage of sulfur and heat value in Btus per pound or kilogram, each obtained by separate determination, are usually reported with the real proximate analysis; and (2) ultimate analysis, which determines the percentages of the chemical elements carbon, hydrogen, oxygen, nitrogen, and sulfur. Other elements that may be present are considered impurities and are reported as ash.

coal ash

Noncombustible matter in coal.

coal auger

A special type of continuous miner. It consists essentially of a large diameter screw drill that cuts, transports, and loads coal onto vehicles or conveyors. The coal auger is used for (1) winning opencast coal without stripping overburden; (2) pillar-and-stall mining; and (3) extraction of pillars or percentage of pillars that would otherwise be uneconomic to work. See also: auger; twist drill; mole mining.

coal ball

Nodules of spheroidal, lenticular, or irregular shape containing petrified plant remains and in some cases animal remains. They vary in size from about 1 to 40 cm or more; occasional specimens weigh more than 1 ton. Infrequently, an entire seam in a restricted area consists largely of coal balls. Coal balls consist mainly of calcareous, dolomitic, sideritic, pyritic, or siliceous material surrounding or impregnating plant and animal remains. They occur in brown coals (mainly sideritic balls) as well as in coals of higher rank generally lying within a coal seam but occasionally in the roof. Calcareous, dolomitic, and pyritic coal balls are commonly found in seams having marine strata in the roof. The distribution in seams is variable. They may occur in a broad zone running through a coalbed or be distributed irregularly in nests. Syn: torf dolomite.

coal bank

An exposed seam of coal.

coal barrier

A protective pillar of coal. See also: barrier pillar.

coal basin

a. Depression in older rock formations in which coal-bearing strata have been deposited. See also: concealed coalfield; exposed coalfield.

b. A coalfield with a basinal structure; e.g., the Carboniferous Coal Measures of England.

coal blasting

There are two methods of breaking coal with explosives, namely, blasting cut coal, which is the method most commonly used, and blasting off the solid, or grunching.


a. A building containing the machinery for breaking coal with toothed rolls, sizing it with sieves, and cleaning it for market.

b. A machine for breaking coal.

coal briquette

Coal made more suitable for burning by a process that forms it into a regular square- or oval-shaped piece.

coal briquetting

See: briquette.

coal bump

Sudden outburst of coal and rock that occurs when stresses in a coal pillar, left for support in underground workings, cause the pillar to rupture without warning, sending coal and rock flying with explosive force.

coal burster

An appliance for loosening coal by means of high-pressure water and oil. It consists of a round, stainless steel bar with small telescopic rams acting on a steel liner in a shot hole. The bar is connected to a hand- or power-operated pump placed near the face. The high-pressure liquid from the pump causes the rams and liner to exert a pressure sufficient to loosen or break down the coal. It is a safe method of coal breaking without the use of explosives. It has not, however, made the progress originally anticipated. See also: water infusion. Syn: hydraulic cartridge.

coal car

A car used in hauling coal in or from a mine.

coal cart

A cart for carrying coal.

coal chute

A trough or spout down which coal slides from a bin or pocket to a locomotive tender, or to vessels, carts, or cars.

coal claim

A piece of land having, or thought to have, valuable coal deposits on it and legally claimed by one seeking to own it.

coal classification

The grouping of coals according to certain qualities or properties, such as coal type, rank, carbon-hydrogen ratio, and volatile matter. See also: high-volatile coals.

coal classification systems

One system classifies coal by the content of volatile matter: with 10% volatile, anthracite; between 10% and 13% lean coal, semianthracite or dry-steam coal; 14% to 20%, variously designated; 20% to 30%, fat or coking coal. Other systems classify by calorific value, and caking and/or coking property. Post-World War II classifications include (1) volatile matter, (2) caking properties on rapid heating, and (3) coking properties. See also: ASTM coal classification.

coal clay

Clay found under a coalbed, usually a fireclay. See also: underclay.

coal cleaning

The sorting, picking, screening, washing, pneumatic separation, and mixing of coal sizes for the market.

coal cleaning equipment

Equipment used to remove impurities -- such as slate, sulfur, pyrite, shale, fire clay, gravel, and bone -- from coal.

coal cleaning plant

A plant where raw or run-of-mine coal is washed, graded, and treated to remove impurities and to reduce ash content. Syn: washery.

coal clearing

The loading of broken coal at the face into conveyors or mine cars. The clearing shift is the coal-loading shift or stint. Usually the miner has a measured task or stint (stent).

coal conglomerate

A conglomerate made of fragments of coal.

coal constituent classification

In the United States it is generally agreed that the maceral concept of the nomenclature Stopes-Heerlen System fails to comprehend the effect of the stage of coalification on the nature of coal constituents. W. Spackman's interpretation of the maceral concept incorporates the ideas of variable coalification in suggesting a skeletal framework upon which a systematic classification can be built. The maceral concept, as interpreted by Spackman, implements the classification of the products of coalification. In this scheme, macerals possessing similar chemical and physical properties are assembled into maceral groups that can, in turn, be characterized by a comparatively restricted set of properties. Maceral groups possessing similar characteristics can be classified into maceral suites. Syn: Spackman system.

coal cutter

a. The longwall coal cutter is a power-operated machine that draws itself by rope haulage along the face, usually cutting out a thin strip of coal from the bottom of the seam, in preparation for shot firing and loading or a cutter loader. The bar and disk machines are obsolescent and the chain coal cutter is now almost universal.

b. See: machineman.

coal-cutter pick

One of the cutting points attached to a cutter chain for making a groove in a coal seam. The picks are made from quality carbon steel or a hard alloy steel and tipped with fused tungsten carbide, sintered tungsten carbide, or other hard-wearing material. The advent of the coal-cutter pick tipped with tungsten carbide on a heat-treated, alloy-steel shank has resulted in marked improvements in drilling and a reduction in cutting delays. See also: chain coal cutter; double-ended pick; duckbill pick; tungsten carbide bit.

coal-cutter team

The miners in charge of a coal cutter. A cutting team varies from two to five with two to three about average. The leading worker is normally stationed in front of the machine and is in charge of the controls, and an assistant follows behind. See also: machineman. CF: back-end man.

coal-cutting machine

A machine powered by compressed air or electricity that drives a cutting chain or other device so as to undercut or overcut a seam, or to remove a layer of shale. Percussive cutters are used to bore holes or to make vertical cuts (nicking, shearing); disk, bar, and chain cutters carry small picks that undercut the seam as the machine travels.

coal-cutting machine operator

See: machineman.

coal digging

A place where coal is dug.

coal drill

Usually an electric rotary drill of a light, compact design. Aluminum and its alloys usually are used to reduce weight. Where dust is a hazard, wet drilling is employed. With a 1-hp (745.7-W) electric drill, speeds up to 6 ft/min (1.83 m/min) are possible. Light percussive drills, operated by compressed air, and hand-operated drills are also employed. See also: electric coal drill.

coal driller

In coal mining, a worker who uses a hand or power drill to drill holes into the working face of the coal into which explosives are charged and set off to blast down the coal.

coal dryer

A plant or vessel in which water or moisture is removed from fine coal. Artificial drying of fine coal is not often employed. Fine coal is removed from wash water by dewatering classifiers or by vacuum filtration. See also: dryer; thermal drying.

coal dust

a. The general name for coal particles of small size. In experimental mine testing, particles that will not pass through a 20-mesh screen-- 1/32-in-square (0.8-mm-square) openings--are not considered as coal dust.

b. In 1964, a series of laboratory tests were made with a spark source on aluminum powder and cornstarch (both dusts presenting a more severe explosion hazard than coal dust). It was found that particles passing a U.S. Standard No. 40 sieve (particles less than 0.016 in or 0.4 mm) contributed to an explosion in the laboratory bomb. The 0.016-in particle diameter was recommended as the definition for dust in surface industry. Thus, two definitions of dust exist. For coal mines, dust consists of particles passing a U.S. Standard No. 20 sieve (particles less than 850 mu m), and for surface industries, dust consists of particles passing a No. 40 sieve (particles less than 425 mu m). The use of two definitions is not incongruous since the potential igniting sources in a coal mine can be much more severe than those in surface industries. c. The dust produced by the breakage and crushing of coal underground and at coal preparation plants. It is usually intermixed with a varying proportion of stone dust. Coal dust in mines presents two main dangers: explosion hazard and pneumoconiosis hazard. The explosibility of a coal dust cloud depends upon its fineness, purity, and volatile content. The dust particles believed to be harmful from the pneumoconiosis aspect are those of 5 mu m and under. In mines, the most common explosive dust encountered is bituminous coal dust. The U.S. Bureau of Mines has established that coal dust in the absence of gas can explode and that explosions can occur in any shape of mine opening. See also: dust-free conditions.

coal-dust explosion

A mine explosion caused by the ignition of fine coal dust. It is considered that an explosion involving coal dust alone is relatively rare. It demands the simultaneous formation of a flammable dust cloud and the means of ignition within it. The flame and force of a combustible gases explosion are the common basic causes of a coal-dust explosion. The advancing wave of the explosion stirs up the dust on the roadways and thus feeds the flame with the fuel for propagation. See also: colliery explosion; gas explosion; stone-dust barrier.

coal-dust index

Percentage of fines and dust passing the 0.0117-in (0.30-mm) mesh or 48-mesh.

coal elevator

A building in which coal is raised and stored preparatory to loading on cars, ships, etc.

coalesced copper

Massive copper made from ground, brittle, cathode copper by briquetting and sintering in a reducing atmosphere at high temperatures with pressure.


See: briquette.

coal face

a. The mining face from which coal is extracted by longwall, room, or narrow-stall system. See also: face.

b. A working place in a colliery where coal is hewn, won, got, or gotten from the exposed face of a seam by face workers.


a. An area of country, the underlying rocks of which contain workable coal seams. The distribution of coalfields was largely determined by folding movements and subsequent denudation. The original coal areas were clearly larger than the present coalfields. See also: coal basin; field.

b. A region in which coal deposits of known or possible economic value occur.

coal flotation

See: flotation; froth flotation.

coal formation

a. A stratigraphic coal-bearing unit in coal measures.

b. A stratum in which coal predominates.

coal fuel ratio

The content of fixed carbon divided by the content of volatile matter is called the fuel ratio. According to their fuel ratios, coals have been classified as anthracite, at least 10; semianthracite, 6 to 10; semibituminous, 3 to 6; and bituminous, 3 or less.

coal-hoisting engineer

In coal mining, one who operates a hoist for raising coal to the surface where separate shafts or compartments are used for handling coal and people.


Those processes involved in the genetic and metamorphic history of coalbeds. The plant materials that form coal may be present in vitrinized or fusinized form. Materials contributing to coal differ in their response to diagenetic and metamorphic agencies, and the three essential processes of coalification are called incorporation, vitrinization, and fusinization. See also: incorporation; carbonification. Syn: incarbonization.


To change vegetal matter into coal.


a. The making of charcoal.

b. The process of supplying or taking coal for use, as in coaling a steamer, etc.

coal interface detector

See: coal interface sensor.

coal interface sensor

Any device that indicates the boundary between the coal and the surrounding strata either at the roof or the floor. Aids the machine operator or control system controls in positioning the coal-cutting head.


A trade name for a smokeless fuel produced by carbonizing coal at a temperature of about 600 degrees C. It has a calorific value of about 13,000 Btu/lb (30.2 MJ/kg) and is used for domestic purposes. Also called semicoke. See also: coking coal.

Coalite process

See: Parker process.

coal land

Land of the public domain that contains coalbeds.

coal lateral

A railroad that parallels a coal road.

coal lead

Thin vein of coal in a fault zone. Coal leads may indicate the direction of a displaced seam. See also: drag.

coal liquefaction

The conversion of coal into liquid hydrocarbons and related compounds by hydrogenation at elevated temperatures and pressures. In essence, this involves putting pulverized bituminous coal into an oily paste, which is treated with hydrogen gas under appropriate conditions of temperature and pressure to form the liquid molecules of carbon and hydrogen that constitute oil. Also called coal hydrogenation. Syn: hydrogenation of coal.

coal measures

a. A succession of sedimentary rocks (or measures) ranging in thickness from a meter or so to a few thousand meters, and consisting of claystones, shales, siltstones, sandstones, conglomerates, and limestones, with interstratified beds of coal.

b. A group of coal seams.

Coal Measures

A stratigraphic term used in Europe (esp. in Great Britain) for Upper Carboniferous, or for the sequence of rocks (typically, but not necessarily, coal-bearing) occurring in the upper part of the Carboniferous System. It is broadly synchronous with the Pennsylvanian of North America.

coal-measures unit

Coal-measures unit strata disclose a rough repetition or cycle of different kinds of rock in the same regular manner. Broadly, the cycle of strata upward is coal, shale, sandstone, and coal. This sequence is sometimes referred to as a unit. See also: cyclothem.

coal mine

Any and all parts of the property of a mining plant, on the surface or underground, that contribute, directly or indirectly, under one management to the mining or handling of coal. In addition to the underground roadways, staple shafts, and workings, a coal mine includes all surface land in use, buildings, structures and works, preparation plants, etc. A colliery. See also: mine.

coal mine explosion

The burning of gas and/or dust with evidence of violence from rapid expansion of gases.

coal mine ignition

The burning of gas and/or dust without evidence of violence from expansion of gases.

coal miner

One employed in the mining of coal.

coal mine regulations

National, State, and local laws, or enforceable rules that govern coal mining.

coal mining

The industry that supplies coal and its various byproducts.

coal mining examinations

The examinations held in respective coal mining States which must be passed by every person who wishes to become a mine foreman, assistant mine foreman, mine examiner, or electrician. A candidate for a certificate may submit himself or herself for a written and oral examination before a Mining Qualifications Board. Holders of approved degrees or diplomas usually need less mining experience to qualify for first-class certification.

coal mining explosives

The statutory requirements regarding the use of explosives in coal mines are very stringent. In gaseous mines only permissible (or permitted) explosives are allowed. See also: explosive.

coal mining methods

The methods of working coal seams have been gradually evolved and progressively improved or modified as knowledge and experience were gained and power machines became available. Over the years, a very large number of methods of mining coal have been developed to suit the seam and local conditions, and they may be split, broadly, into longwall, and pillar methods of working. See also: stowing method.

coal oil

Crude oil obtained by the destructive distillation of bituminous coal.

coal patch

A small settlement near a coal mine.

coal penetrometer

An instrument to assess the strength of a coal seam, its relative workability, and the influence of roof pressure. It consists of a steel rod of sectional area 1/4 in (super 2) (1.6 cm (super 2) ) that is pushed into the coal, normal to the coal face, under the action of a light hydraulic ram. The ram is braced against lightweight props erected at the face. When in position, the penetrometer gives a graph of load against penetration at a particular point. Readings are taken at a number of points laterally and vertically along the face, and these can be correlated with the performance of plow-type machines. Thus, the probable performance of a machine in a seam can be estimated without the need for costly trials. Syn: penetrometer.


Eng. A place where coal is dug. A coal mine.

coal planer

A type of continuous coaling machine developed in Germany esp. for longwall mining. It consists of a heavy steel plow with cutting knives, with power equipment to drag it back and forth across a coal face. A parallel conveyor receives and carries away the coal as the planer digs it from the face.

coal plant

A fossil plant found in coalbeds or contributing its substance to the formation of coalbeds. Any plant species, the residue of which has entered into the composition of coal under natural geological conditions.

coal plow

a. A cutter loader with knives to slice the coal off the face.

b. This device carries steel blades that shear or plane off coal to a limited depth and plow it onto the face conveyor. The plow is hauled backward and forward along the coal face by steel ropes or chains operated by winches in the gate roads, and it planes off a thickness of 11.8 in (30 cm) to a height one-third to one-half the seam thickness each time. The coal is conveyed along the face by a double-chain conveyor with double-ended drive; the conveyor sections are articulated to allow for bends in its tracks and are moved bodily forward at each passage of the plow, either by compressed-air jacks or by means of a torpedo or trailer attached by rope to the plow and an auxiliary drum on the winches. Its uses are limited to softer coal seams, or to suitably prepared coal. Also called kohlenhobel.

coal pocket

a. A structure, bunker, or bin for the storage of coal.

b. An arrangement of bins to load trucks or railcars by gravity.

coal preparation

The various physical and mechanical processes in which raw coal is dedusted, graded, and treated by dry methods (rarely) or water methods, using dense-media separation (sink-float), jigs, tables, and flotation. The objective is the removal of free dirt, sulfur, and other undesirable constituents.

coal-preparation plant

a. A facility where raw coal is sized and prepared for loadout. In the United States, plant capacities vary from 500 to 2,500 st/h (454 to 2,268 t/h). See also: cleaning; dense-medium washer; gravity concentration; screen; washery.

b. A facility or collection of facilities that include associated support facilities and consist of, but are not limited to: loading facilities; storage and stockpile facilities; sheds, shops, and other buildings; settling basins and impoundments, coal processing and other waste disposal areas; roads, railroads, and other transport facilities. Exempted from the meaning of coal-preparation plant is an operation that a) loads coal; b) does not separate coal from its impurities; and c) is not located at or near the mine site.

coal-preparation process

The process adopted for cleaning and sizing coal for the market. Specialists select the best process for any particular run-of-mine coal. Many conflicting factors must be weighed. The cost of a detailed investigation is well repaid in higher recoveries, in flexibility, and in ease of operation and maintenance.

coal-preparation shift

On mechanized longwall faces, the shift during which coal-cutting, boring, and shot-firing operations are performed.

coal-processing waste

Earth materials that are combustible, physically unstable, or acid- or toxic-forming, which are wasted or otherwise separated from product coal. They are slurried or otherwise transported from coal-preparation plants, after physical or chemical processing, cleaning, or concentrating of coal.

coal rank

Classification according to degree of metamorphism or progressive alteration, in the natural series from lignite to anthracite; higher rank coal is classified according to fixed carbon on a dry basis; lower rank coal according to Btus on a moist basis.

coal rash

Very impure coal containing much argillaceous material, fusain, etc.

coal room

a. Scot. A working face in stope-and-room workings.

b. The open area between pillars where the coal has been removed.

coal sampling

The standard method used by the U.S. Bureau of Mines samplers is as follows: A space of 5 ft (1.52 m) in width should be cleared of dirt and powder from top to bottom of the seam being sampled. Down the center of this cleared space, a zone 1 ft (0.3 m) wide is cut to a depth of at least 1 in (2.54 cm) in order to get perfectly clean coal. A cut is then made up the center of this zone to a depth of 2 in (5.2 cm) and a width of 6 in (15.2 cm); or, if the coal is soft, to a depth of 3 in (7.6 cm) and a width of 4 in (10.2 cm). Approx. 5 to 6 lb (2.3 to 2.7 kg) of coal will be obtained for each foot (0.3 m) of thickness of the seam. This should include all bony coal included in the mining operation and exclude all slate or partings, which are thrown out during the operation. The sample obtained should be collected on a waterproof cloth 6 ft by 7 ft (1.83 m by 2.13 m) and then screened, the lumps being broken in a mortar, and all passed through a 1/2-in (12.7-mm) screen. Any impurities, such as slate or pyrite, are crushed to 1/4 in (6.4 mm) or finer and thoroughly mixed with the coal. The coarser materials should be evenly distributed, the sample being then quartered, remixed, and requartered. When the mixing is complete, the sample should be placed in a can with the capacity of 3 lb (1.35 kg) and the top screwed on and sealed with adhesive tape. The can should be labeled with the name of the collector, the location, the date, and any other information necessary for the analysis. See also: channel sample; sampling.

coal seam

A bed or stratum of coal.

coal-seam correlation

The identification of a coal seam; the linking up or matching of a seam exposed in different parts of a mine or coalfield. A coal seam may be correlated by lithology, by fossils, by chemical composition, or by its spore content. Coal-seam correlation is very important in exploration and in penetrating faults. See also: correlation.

coal-sensing probe

An obsolete, nucleonic coal-sensing instrument that can measure the thickness of coal left on the roof or floor of a seam after the passage of a mining machine. The principle used is the measurement of the density of the strata underlying the machine by a gamma-ray backscattering unit. Gamma rays from a radioactive source are scattered in all directions by the atomic particles in the coal and rock. The amount of scattered radiation eventually reaching the Geiger counter is, approx., inversely proportional to the density of the scattering medium; i.e., more radiation will come back from coal than from rock. Thus, as the amount of coal between the source and the underlying rock changes, so the amount reaching the Geiger counter and the counting unit (the ratemeter) will change, and consequently the output of the meter can be calibrated in terms of the thickness of the floor coal. This instrument has been replaced by a natural-gamma coal thickness sensor. See also: manless face.

coal separator

A machine that separates coal from associated impurities in run-of-mine material. See also: coal-preparation plant.

coal slime

A slurry containing particles of such size range that 50% or more (by weight) will pass a 200-mesh sieve (or finer).

coal sludge

A slurry that has been partly dewatered by sedimentation, usually to a dilution that will permit further dewatering by mechanical means.

coal slurry

Finely crushed coal mixed with sufficient water to form a fluid. To use coal slurry pumped through a pipeline as fuel, expensive drying and dewatering pretreatment has been necessary. Recent tests indicate that coal slurry can be fired in a cyclone furnace as it is received from a pipeline; i.e., a coal and water mixture. See also: slurry.

coal smoke

A suspension of very fine particles in air. A coal that breaks down easily when heated gives off its volatile matter very easily and perhaps more quickly than the available draft can supply the air for combustion, with the result that dark smoke containing much unburnt or partly burnt material is given off--a loss of fuel energy. See also: smoke.

Coal special

Explosive; used in mines.

coal split

See: split seam.

coal spragger

a. In bituminous coal mining, one who sets short wooden props in a slanting position (sprags) under the upper or overhead section of a bed of coal to hold that section up while the lower section is being mined, or wedges heavy slanting props (sprags) against the coal to prevent it from flying when broken down by blasting.

b. One who places short pointed wooden sprags between the spokes of a mine car wheel to stop the car.

coal stripper

In bituminous coal mining, a general term applied to a worker who is engaged in mining coal in a strip mine, one in which the coal is close enough to the Earth's surface to permit the use of power shovels in stripping back the ground and loading the coal into large cars or trucks. Usually designated according to particular jobs.

coal substance

Coal excluding its mineral matter and moisture.

coal tar

Tar obtained by the destructive distillation of bituminous coal, usually in coke ovens or in retorts, and consisting of numerous constituents (such as benzene, xylenes, naphthalene, pyridine, quinoline, phenol, cresols, light oil, and creosote) that may be obtained by distillation.

coal-tar oil

Oil obtained by the distillation of coal tar. Oils are classified into light and heavy oils. A light oil is one having a specific gravity less than 1.000 and contains the coal-tar napthas. Heavy oils sink in water and contain such compounds as creosote, anthracene, anthracene oil, etc.

coal-tar pitch

A dark-brown to black residuum from the distillation of coal tar, ranging from a sticky mass to a brittle solid, depending on the degree of distillation. Most coal-tar pitch melts between 60 degrees C and 70 degrees C.

coal testing

Evaluating coals by methods other than chemical, such as determining the relative values of different coals as fuels by burning them under controlled conditions in furnaces, or determining their gas- and coke-producing properties by testing in a retort. The term coal testing is frequently erroneously used, esp. in coal marketing, for coal analysis.

coal thickness sensor

Any measurement instrument that is designed to measure the thickness of the coal remaining on the mine roof or floor after coal is removed by mining.

coal tipple

See: tipple.

coal type

a. A variety of coal, such as common banded coal, cannel coal, algal coal, and splint coal. The distinguishing characteristics of each type of coal arise from the differences in the kind of plant material that produced it.

b. A coal, particularly a bituminous coal, contains dissimilar bands or layers that are believed to have been formed mainly from selected portions of the plant material forming the seam. These bands, which have been given the terms vitrain, clarain, durain, and fusain, are the different types of coal in that seam. See also: vitrain; clarain; durain; fusain.

coal washer

A place where mined coal is treated by sink-float methods or by froth flotation to remove ash, shale, sulfur, and other unwanted products. The resulting clean coal product is graded to size and regulated for maximum ash content. Also called cleaning plant; preparation plant.

coal wheeler

In the iron and steel industry, a laborer who shovels coal into a wheelbarrow and pushes it to a furnace.

coal workings

A coal mine with its appurtenances; a colliery. Coal works.


A place where coal is stored.

coarse aggregate

The portion of an aggregate retained on the No. 4 sieve, consisting of particles with diameters greater than 4.76 mm. CF: aggregate; fine aggregate.

coarse gold

Gold in large grains, as distinguished from gold dust. Also called coarse quartz gold.


Applied to rocks composed of large grains; used mainly in a relative sense, but an average size greater than 5 mm in diameter has been suggested. CF: medium-grained; fine-grained.

coarse-grained soil

A soil in which gravel and sand predominate. Coarse-grained soils are those least affected by moisture-content changes as most surface rain, etc., becomes gravitational water.

coarse jig

A jig used to handle the larger sizes and heavier grades of ore or metal.

coarse metal

An iron-and-copper matte containing sulfur; a product of copper smelting in a reverberatory furnace.

coarse roll

A large roll for the preliminary crushing of large pieces of ore, rock, or coal. Used in stage crushing.

coarse sand

a. A geologic term for a sand particle having a diameter in the range of 0.5 to 1 mm (1 to 0 phi units). Also, a loose aggregate of sand consisting of coarse sand particles. See also: sand.

b. An engineering term for a sand particle having a diameter in the range of 2 mm (retained on U.S. standard sieve No. 10) to 4.76 mm (passing U.S. standard sieve No. 4).

coaxial cable

Electrical cable with inner conducting wire covered by alternating layers of insulating and conducting material.


a. Corn. To break ore with hammers so as to sort out the valuable portion.

b. Derb. A small solid pillar of coal left as a support for the roof.


Uncemented sand or gravel underlying the nitrate (caliche) deposits of Chile. See also: congela.


A tough, lustrous, nickel-white or silvery-gray, metallic element. Symbol, Co. Occurs in the minerals cobaltite, smaltite, and erythrite; often associated with nickel, silver, lead, copper, and iron ores, from which it is most frequently obtained as a byproduct. Its alloys have unusual magnetic strength and are used for high-speed, heavy-duty, high-temperature cutting tools, and for dies, in jet turbines and gas turbine generators. Its salts are used in porcelain, glass, pottery, tiles, and enamels to produce brilliant blue colors.

cobalt bloom

Hydrated arsenate, Co (sub 3) (AsO (sub 4) ) (sub 2) .2H (sub 2) O . See also: erythrite.


Particles of a refractory material, such as powdered tungsten carbide, cemented together with cobalt to form a metallike mixture.

cobalt glance

See: cobaltite.

cobaltiferous wad

An impure hydrated oxide of manganese containing up to 30% cobalt; a source of cobalt in Zaire.


a. An orthorhombic mineral, 4[CoAsS] ; pseudocubic; metallic; occurs in high-temperature vein deposits associated with smaltite and in metamorphic rocks; an important source of cobalt. Syn: cobalt glance; white cobalt; gray cobalt.

b. The mineral group cobaltite, gersdorffite, hollingworthite, irarsite, platarsite, tolovkite, ullmannite, and willyamite.

cobalt lollingite

See also: safflorite. Also called cobaltiferous lollingite.

cobalt melanterite

See: bieberite.

cobalt-nickel pyrite

a. A name applied by Vernadsky to a steel-gray member of the pyrite group containing 11.7% to 17.5% nickel and 6.6% to 10.6% (Fe,Ni,Co)S (sub 2) ; small, pyritohedral crystals; isometric. Probably a mixture of siegenite and pyrite. From Musen, Westphalia, Germany.

b. As applied by Henglein, a syn. for hengleinite. See also: hengleinite.


A pale rose-red to carmine variety of adamite in which cobalt replaces some of the zinc.


a. Replaces the generally accepted name sphaerocobaltite for rhombohedral CoCO (sub 3) . Not the cobaltocalcite of F. Millosevich, 1910, a red cobaltiferous variety of calcite.

b. A former name for sphaerocobaltite.

cobalt ocher

See: erythrite; asbolan; asbolane.


A peach-blossom-red rhombohedral variety of siderite with moderate substitution of cobalt for iron. Also spelled cobaltospharosiderite.

cobalt pentlandite

An isometric mineral, Co (sub 9) S (sub 8) ; pentlandite group.

cobalt pyrites

a. See: linnaeite.

b. Cobaltiferous pyrite containing up to 14% cobalt; an ore of cobalt in Zambia.

cobalt-rich crust

An authigenic deposit of iron-manganese oxides enriched with cobalt. These crusts may contain potentially commercial quantities of manganese (20% to 30%), copper, nickel, and cobalt (less than 3% combined), but are primarily evaluated on the basis of their cobalt content. They are found as encrustations on exposed rocky seabeds on island slopes, seamounts, or submerged plateaus in water depths between 800 m and 2,400 m. The crusts may be up to 40 cm thick, but are more commonly 3 to 5 cm. They often occur in association with platinum and phosphorite.

cobalt skutterudite

The pure end member, CoAs (sub 3) , of the skutterudite series. Syn: skutterudite.

cobalt vitriol

See: bieberite; rose vitriol.

cobbed ore

Eng. Ore broken from veinstone by means of a small hammer.


a. The separation, generally with a handheld hammer, of worthless minerals from desired minerals in a mining operation; e.g., quartz from feldspar. Syn: hand cobbing; piking.

b. Rubble, such as from furnace bottoms, impregnated with copper.

cobbing board

A flat piece of wood used in cobbing.

cobbing hammer

A special chisel type of hammer used to separate the mineral in a lump from the gangue in the hand-picking of ores.


a. A usually rounded or semirounded rock fragment between 3 to 12 in (76 to 305 mm) in diameter; large than a pebble and smaller than a boulder, rounded or otherwise abraded in the course of aqueous, eolian, or glacial transport. Syn: cobblestone.

b. Eng. Small lump coal. See also: cob coal.

cobble riffle

A sluice with a cobble-paved bottom used in placer mining.


A graded size of anthracite below large coal--about 5 in (12 cm).


a. A naturally rounded, usually waterworn stone suitable for use in paving a street or in other construction. Syn: cobble; roundstone.

b. A consolidated sedimentary rock consisting of cobble-size particles.


Eng. Cleaning the haulage road of coal that has fallen off the trams.

cob coal

A large round piece of coal.


Upper Lower Devonian.

cobra stone

See: chlorophane.

cocarde ore

See: cockade ore.


a. A mixture of chalcocite and silver.

b. A silver-gray copper silver sulfide found at Ramos, Mexico; perhaps a variety of stromeyerite.

cockade ore

a. An open-space vein filling in which the ore and gangue minerals are deposited in successive comblike crusts around rock fragments; e.g., around vein breccia fragments. Syn: cocarde ore; sphere ore. See also: ring ore.

b. Cockscomb pyrite; a form of marcasite.

cockade structure

The form taken by cockade ore.


To set supports in herringbone fashion.


Herringbone supports. A method of support by which a center support of beams or bars running longitudinally along the roof of a road is supported systematically by slanted struts or props with their feet spragged in the side of the road, the whole looking like a herringbone.


Temporary support for the coal face. A short crosspiece is held to it by two slanting props, one hitched in the floor, the other in the roof.


See: cockermeg.


See: cockermeg.


a. Corn. Schorl or black tourmaline.

b. Any mineral occurring in dark, long crystals, esp. schorl. c. Eng. A black, thready mineral, seeming to be a fibrous talc; occurs in Cornish tin mines. d. Eng. An ironstone nodule. e. Cornish name for hard siliceous rocks.


A piece of slate or bony.

cockscomb pyrite

See: marcasite.

cockscomb pyrites

A crestlike variety of marcasite. See also: marcasite.

cocoa mat

A fabric of wood fibers used to distribute water evenly over a smooth surface.

codorous ore

A highly siliceous hematite containing only a trace of phosphorus, but high in potash.

coefficient of absolute viscosity

See: coefficient of viscosity.

coefficient of acidity

A ratio, calculated from the normative molecular proportions of the constituents of a rock or slag; e.g., number of atoms of oxygen in SiO (sub 2) / number of atoms of oxygen in the basic oxides.

coefficient of compressibility

The decrease in volume per unit volume produced by a unit change of pressure.

coefficient of elasticity

See: modulus of elasticity.

coefficient of friction

a. A numerical expression of the relationship between pressure and the resistance force of friction.

b. A quantity used to calculate the head loss in a fluid or air. The loss is a function of surface roughness, wetted perimeter, and velocity of the fluid or gas.

coefficient of heat transmission

The quantity of heat transmitted from fluid to fluid per unit of time per unit of surface area through a material or arrangement of materials under a unit temperature differential between fluids. Commonly used for building materials. Syn: heat transmission coefficient.

coefficient of permeability

The rate of flow of water under laminar flow conditions through a unit cross-sectional area of a porous medium under a unit hydraulic gradient and a standard temperature, usually 20 degrees C. See also: permeability.

coefficient of rigidity

See: modulus of rigidity.

coefficient of thermal diffusion

A thermal property of matter with the dimensions of area per unit time; it corresponds to the thermal conductivity divided by the product of density and heat capacity.

coefficient of traction

Represents the percentage of the total engine power that can be converted into forward motion by means of the friction between tire and track.

coefficient of velocity

The rate of transformation of a unit mass during a chemical reaction.

coefficient of viscosity

a. The shearing force per unit area required to maintain a unit difference in velocity between two parallel layers of fluid a unit distance apart. Syn: coefficient of absolute viscosity.

b. The ratio of the shear stress in a substance to the rate of shear strain. See also: viscosity.


A triclinic mineral, (Ca,Cu)Al (sub 6) (PO (sub 4) ) (sub 4) (OH) (sub 8) .4H (sub 2) O ; turquoise group; occurs in white to pale-blue fibrous crusts.


A monoclinic mineral, SiO (sub 2) ; polymorphous with cristobalite, quartz, tridymite, and stishovite; insoluble in hydrogen fluoride.

coffee shale

Drillers' term in the Appalachian basin for well cuttings of dark-colored shale chips mixed wih light-colored mud.


a. A rectangular plank frame, used in timbering levels. Also spelled cofer.

b. A floating dock; a caisson.


a. A set of temporary walls designed to keep soil and/or water from entering an excavation.

b. A method of shaft sinking through saturated sand or mud near the surface. A cofferdam is an enclosure, open to the air, that keeps water out of the shaft area to allow excavation to proceed. The enclosing wall is constructed by driving down strips of steel with interlocking edges or concrete piles, reinforced with steel. In general, cofferdams are used only for short lengths and where piles can be driven into an impervious deposit, so that normal pumping will keep the shaft sufficiently dry for working. See also: drop shaft; piling.


A method of shaft sinking through loose, watery, or running ground. It consists in lining the shaft with a thick wall, made of brick and cement or brick and hydraulic lime with puddled clay in all cavities. Used for keeping back surface water but the method is now somewhat obsolete.


a. Corn. An old, open-mine working, in which the ore is cast up from platform to platform. See also: goffan.

b. A heavily shielded shipping cask for spent fuel elements. Some coffins weigh as much as 75 st (68 t).


A naturally occurring uranium mineral, U(SiO (sub 4) ) (sub 1-x) (OH) (sub 4x) ; sp gr, 5.1; luster adamantine; color black; commonly fine-grained and mixed with organic matter and other minerals. Found in Colorado, Utah, Wyoming, and Arizona. An important ore of uranium in some mines on the Colorado plateau.


a. Straight timbers set in a large bunch. They should be firmly set and as close together as possible. Sometimes 12 to 20 are set at one location. Under conditions where single straight posts will not suffice to control the top, and yet cribs are not needed, the use of cogs may be advantageous. May also be called a battery. See also: pigsty; cogging.

b. A crib made of notched timbers built up like a log house. A chock, cob, corncob, or crib. If the timbers are squared instead of notched, the structure is called a nog. It is ordinarily filled with waste, and rocks are put between the timbers. See also: chock. c. A rock intrusion. d. To consolidate ingots or shape them by hammering or rolling. e. An inserted tooth as in a cogwheel. Gears are often improperly referred to as cogwheels.


a. The operation of rolling or forging an ingot to reduce it to a bloom or billet.

b. The propping of the roof in longwall stalls. Also spelled coggin. See also: cog.

cogging mill

A blooming mill, usually consisting of a two-high reversing mill with two rolls, 0.6 to 1.2 m in diameter, between which a hot ingot is reduced to blooms or slabs.


A rounded, waterworn stone, esp. of the size suitable for paving; a cobble; also called cogglestone. Same as cobblestone.

cognate fissure

One fissure of a system of fissures that originated at the same time from the same causes as other fissures in the same system. Cognate may similarly apply to fractures and joints.

cognate inclusion

See: autolith.

cognate xenolith

See: autolith.

cogwheel ore

A miners' name for bournonite. Same as wheel ore.


a. An orthorhombic mineral, (Fe,Ni,Co) (sub 3) C ; an accessory in iron meteorites.

b. An iron carbide phase in steel. See also: cementite.


Property of like mineral grains that enables them to cling together in opposition to forces tending to separate them. CF: adhesion.

cohesionless soil

a. A soil that when unconfined has little or no strength when air-dried, and that has little or no cohesion when submerged.

b. A frictional soil, such as sand, gravel, or clean silt.

cohesive soil

a. A soil that when unconfined has considerable strength when air-dried, and that has significant cohesion when submerged.

b. A sticky clay or clayey silt as opposed to sand.

coil load

The total amount of heat, in British thermal units per hour, that must be removed from the air by the cooling coils.


a. A closed-die squeezing operation, usually performed cold, in which all surfaces of the work are confined or restrained, resulting in a well-defined imprint of the die upon the work.

b. A restriking operation used to sharpen or change an existing radius or profile. c. In powder metallurgy, the final pressing of a sintered compact to obtain a definite surface configuration. (Not to be confused with repressing or sizing.)

coinstone bed

Cement stone band. Stone suitable for coinstones, quoinstones, and cornerstones, used in building.


a. Bituminous coal from which the volatile constituents have been driven off by heat, so that the fixed carbon and the ash are fused together. Commonly artificial, but natural coke is also known; e.g., where a dike has intersected a bituminous coalbed and has converted the bordering coal to natural coke.

b. A derogatory syn. for carbon; carbonado; black diamond. See also: char.

coke breeze

The fine screenings from crushed coke or from coke as taken from the ovens, of a size varied in local practice but usually passing a 1/2-in (12.7-mm) or 3/4-in (19.0-mm) screen opening.

coke coal

a. N. of Eng. Carbonized or partially burnt coal found on the sides of dikes. See also: natural coke.

b. Coal altered by an igneous intrusion.

coke drawer

In the coke products industry, a laborer who removes coke from beehive ovens by hand.

coke dust

Coal dust that has been coked by the heat of an explosion and has assumed different forms under different conditions; usually found either near the origin of the explosion or in a room or wide place where the velocity of the explosion is low and there is insufficient oxygen for complete combustion of the coal dust. The volatile matter of coal dust seems to burn first and, if the coal is a coking coal, coke is formed of one kind or another, depending on the position, temperature, size of the dust, and velocity of the explosion. Also called coked dust.

coke iron

Iron made in a furnace using coke as fuel.


Coal altered by an igneous intrusion. Syn: carbonite. See also: natural coke.

coke mill

A mill used in the foundry for the grinding of coke for the production of blacking.

coke oven

A chamber of brick or other heat-resistant material in which coal is destructively distilled. Coke ovens are of two principal types: (1) beehive ovens, which were originally built round with a spherical top like an old-fashioned beehive. They had an opening in the top and various small openings for draft at the base. The ovens were developed into banks (rows) of joining cubicles; coke in long columnar pieces is characteristic and is still known as beehive coke. Tar, gas, and other byproducts are lost. (2) Byproduct ovens, which were built in rectangular form with the front and back removable, but so arranged that they may be luted to practical gastightness and all byproducts gaseous at the high temperatures may be pumped out.

coke person

In the foundry industry, a laborer who unloads, stores, and conveys coke within the foundry.

coke tower

A high tower or condenser filled with coke. Used in the manufacture of hydrogen chloride gas to give a large surface for the union of a falling spray of water with the rising hydrochloric acid gas.

coking coal

Coal that can be converted into useful coke that must be strong enough to withstand handling. There is no direct relation between the elementary composition of coal and coking quality, but generally coals with 80% to 90% carbon on a dry, ash-free basis are most satisfactory. See also: caking coal; bituminous coal; Coalite.

coking stoker

A mechanical stoker or device for firing a furnace that allows the coal to coke before feeding it to the grate, thus burning the fuel with little or no smoke.

colander shovel

An open wirework shovel used for taking salt crystals from an evaporating brine.

cold bed

A platform in a rolling mill on which cold bars are stored.

cold blast

Air forced into a furnace (e.g., cupola) without being previously heated. See also: Gayley process.


Cracks in cold, or nearly cold, metal, due to excessive internal stress caused by contraction. Formation of cracks may be caused by the mold being too hard or the design of a casting being unsuitable.


To draw (as metal) while cold or without the application of heat.


The process of reducing the cross-sectional diameter of tubes or wire by drawing through successively smaller dies without previously heating the material, thereby increasing its tensile strength. Steel wire for prestressing is made by this process.

cold-extractable metal

See: readily extractable metal.

cold galvanizing

Application of powdered zinc, in suspension in an organic solvent, to iron articles. On evaporation of the solvent an adherent coating of zinc remains.

cold noser

See: wildcatter.


Running an unhoused drill in cold weather.


To roll (metal) without applying heat.


Said of metal that has been rolled at a temperature close to atmospheric. The cold rolling of metal sheets results in a smooth surface finish.

cold saw

A saw for cutting cold metal.

cold shot

A portion of the surface of an ingot or casting showing premature solidification caused by a splash of metal during pouring.

cold soldering

Soldering in which two pieces are joined without heat (as by means of a copper amalgam).

cold working

Shaping of metals at ordinary temperatures; cold-drawing, rolling, stamping. Within limits, in treatment of iron, copper, aluminum, induces work hardening, thus increasing strength. If carried too far, brittleness results. Metal that is brittle when cold is termed cold-short.

cold zone

The preheating zone of a rotary cement kiln.


A natural hydrated calcium borate, Ca (sub 2) B (sub 6) O (sub 11) .5H (sub 2) O ; white or colorless; white streak; vitreous to dull luster; Mohs hardness, 4 to 4.5; sp gr, 2.26 to 2.48; found in California. One of the raw materials in the United States for boric acid, sodium borate, etc.

Cole reagent

Solution of 10 g stannous chloride, 95 mL water, 5 mL HCl, and 10 g pyrogallol. Viscose silk impregnated with this turns red to violet in solution containing gold.


a. A subvariety of euvitrain. It consists of redeposited ulmin compounds precipitated from solution and observable microscopically.

b. Approved by the Heerlen Congress of 1935 as applicable to vitrain in which plant structure is not visible. Adopted as collite, spelled collit in German but retaining the ain ending in English and French usage. CF: ulmain.


Complete cave-in of walls of a borehole or mine workings.

collapse breccia

A breccia formed by the collapse of rock overlying an opening, as by foundering of the roof of a cave or of the roof of country rock above an intrusion; e.g., a solution breccia. Syn: founder breccia.

collapsing strength

The load expressed in pounds or tons, which, if exceeded, results in the collapse of a structure, such as a drill tripod, derrick, or A-frame.


a. In a mine shaft, the first wood frame of the shaft; sometimes used in reference to the mouth or portal of the tunnel.

b. Supporting framework at top of shaft from which linings may be hung. c. The junction of a mine shaft and the surface. d. The beginning point of a shaft or drill hole, the surface. e. The mouth of a mine shaft. f. The bar, or crosspiece, in a framed timber set. g. The term applied to the timbering or concrete around the mouth or top of a shaft. h. Scot. A frame to guide pump rods; the fastening of pipes in a shaft. i. The mouth or opening of a borehole or the process of starting to drill a borehole. j. A pipe coupling or sleeve. k. See: friction head. l. A sliding ring mounted on a shaft so that it does not revolve with it. Used in clutches and transmissions.

collar distance

The distance from the top of the powder column to the collar of the blasthole, usually filled with stemming.


A started hole drilled sufficiently deep to confine the drill bit and prevent slippage of the bit from normal position.

collar in

The act or process of beginning a borehole.


a. The process of beginning the drilling of a borehole, or the excavation of a mine shaft.

b. Eng. Timber framing for supporting pump trees in a shaft. See also: chog. c. The term used to indicate that metal passing through a rolling mill follows one of the rolls so as to encircle it.

collaring a hole

The formation of the front end of a drill hole, or the collar, which is the preliminary step in drilling to cause the drill bit to engage in the rock.

collaring bit

A fishtail-, spudding-, or other-type bit used exclusively for beginning a borehole.


In rolling mills, the sections of larger diameter separating the grooves in rolls used for the production of rectangular sections.

collar structure

A heavy wooden frame erected at the mouth of a rectangular shaft to provide a solid support for the timber sets. A more permanent structure consists of a concrete wall extending from two to eight sets in depth. On this concrete mass is bolted the bearer timbers that support the top heavy set or collar set. The term also applies to the heavy concrete ring at the mouth of a circular concrete-lined shaft. Syn: shaft collar.


See: ludwigite.

collecting agent

A reagent added to a pulp to bring about adherence between solid particles and air bubbles.

collective subsidence

That condition in sedimentation in which the particles and flocs are sufficiently close together to retard the coarse fast-settling particles while the slow-settling ones are entrapped and carried down with the mass.


A heteropolar compound containing a hydrogen-carbon group and an ionized group, chosen for ability to adsorb selectively in a froth flotation process and render adsorbing surfaces relatively hydrophobic. A promoter.


a. Strictly speaking, a person who mines coal with a pick, though commonly applied to anyone who works in or about a colliery. Also called hewer; stallman.

b. A steam or sailing vessel carrying a cargo of coal. c. A coal merchant or dealer in coal.


Explosive; used in mines.

collier's lung

See: anthracosis.


a. An entire coal mining plant, generally used in connection with anthracite mining, but sometimes used to designate the mine, shops, and preparation plant of a bituminous operation.

b. A coal mine. c. A ship, or ships, used in the coal trade.

colliery bailiff

Derb. The superintendent of the colliery.

colliery consumption

That part of the coal output at a colliery that is used for steam generation and other purposes connected with the working of the colliery itself.

colliery explosion

An explosion in the workings or roadways of a colliery as a result of the ignition of combustible gases or coal dust or a mixture of both. See also: coal-dust explosion; methane; stone-dust barrier.

colliery plan

Gr. Brit. A map of the mine workings, and sections of the shafts and seams being worked, which the colliery manager must keep at the pithead office in accordance with the Surveyors and Plans Regulations, 1956, of the Act.

colligative properties

These are properties only of solutions and include vapor pressure, freezing point, boiling point, and osmotic pressure changes that occur with changes in the characteristics of the solution. Seawater does not follow the general rules of solutions, but departures are proportional.

collimating mark

See: fiducial mark.


a. Alignment axially of parts of an optical system. Collimation error is due to the line of sight of a survey instrument not coinciding with traversing gear, scales, or leveling devices. The collimation line is the line of sight, passing through the intersection of the crosshairs of the reticule. The collimation method is the height-of-instrument method of leveling whereby fore-and-aft readings are made on a leveling staff by an instrument placed intermediately so that the rise or fall between the fore station and the back station is shown by a change in the staff reading. See also: rise and fall.

b. Conversion of a divergent beam of energy or particles into a parallel beam.

collimation line

The line of sight of a surveying instrument that passes through the intersection of the cross hairs in the reticule.


A maceral of coal within the vitrinite group, consisting of homogeneous jellified and precipitated plant material, lacking cell structure and of middle-range reflectance under normal reflected-light microscopy. See also: vitrinite. CF: ulminite.


A triclinic mineral, Ca (sub 2) (Mg,Fe)(PO (sub 4) ) (sub 2) .2H (sub 2) O; fairfieldite group; forms fibrous nodules.

collision blasting

Blasting in which different sections of the rocks are blasted out against each other.

collision waves

Two waves that are propagated in opposite directions through the burned gases, and originating at the point where two explosion waves meet.


Another name for euvitrain. See also: collain.


Said of the rounded, finely banded kidneylike mineral texture formed by ultra-fine-grained rhythmic precipitation once thought to denote deposition of colloids. CF: botryoidal; reniform.


A substance composed of extremely small particles, ranging from 0.2 to 0.005 mu m, which when mixed with a liquid will not settle, but remain permanently suspended; the colloidal suspension thus formed has properties that are quite different from those of the simple, solid-liquid mixture or a solution.

colloidal clay

A clay, such as bentonite, which, when mixed with water, forms a gelatinous-like liquid.

colloidal fuel

A mixture of finely pulverized coal and fuel oil, which remains homogeneous in storage. It has a high calorific value and is used in oil-fired boilers as a substitute for fuel oil alone.

colloidal mud

A drilling mud in which the gelatinous constituents, such as bentonite, will remain in suspension in water for a long time.

colloidal particles

Particles so small that their surface activity has an appreciable influence on the properties of its aggregate.

colloidal sulfur

Amorphous sulfur in a finely divided condition. Prepared by the action of dilute sulfuric acid on sodium thiosulfate or by the reaction of hydrogen sulfide and sulfurous acid. Also prepared by mixing equivalent solutions of hydrogen sulfide and sulfur dioxide. Forms a clear yellow solution containing very minute suspended particles of sulfur; the addition of alum immediately precipitates the sulfur. Also called milk of sulfur.

colloid mill

Grinding appliance such as two disks set close and rotating rapidly in opposite directions, so as to shear or emulsify material passed between them.

colloid minerals

Minerals deposited as gradually hardening gelatinous or flocculent masses instead of assuming crystalline form; may apply to some deposits of malachite, hematite, and psilomelane. CF: botryoidal; reniform.


Generic designation for massive, amorphous, cryptocrystalline to fine-grained apatite or phosphate that constitutes the bulk of phosphate rock and fossil bone; not a true mineral species; analogous to the terms limonite and bauxite. Syn: collophanite.


See: collophane.

Collum washer

Mineral jig with a quick down stroke and retarded return of its plunger.

Colmol mining machine

A machine in which the coal is hewed from the solid by 10 rotating chipping heads in 2 rows of 5, each with the lower row in advance of the upper. Each head consists of a bit supplemented by widely spaced teeth, each tooth being stepped back to the outside of the head. The circular kerfs made by the heads overlap, and as the machine moves forward, the effect is to break the coal ahead of the teeth into the free spaces, thereby minimizing the production of fines.

Cologne umber

An earthy black or brown lignite used as a pigment. Etymol. source near Cologne, Germany.


A noncommittal term for members of the columbite-tantalite series.


a. A trace of metallic gold found in a prospector's pan after a sample of soil or of gravel has been panned out. Prospectors say, e.g., the dirt gave so many colors to the panful.

b. The shade or tint of the soil or rock that indicates ores; e.g., gossan coloration. c. Color is an important property used in megascopic and microscopic determination of minerals. It depends on the selective absorption or reflection of certain wavelengths of light by the mineral during transmission or reflection. The color of metallic (or metal-bearing) minerals is a fairly constant property, whereas that of nonmetallic minerals is generally less so owing to the pigmentation effect of minor impurities. The color of a massive mineral is commonly different from that of its powder or streak. d. The Munsell notation has come into wide use for the designation of colors of rocks and soils. In this system, a color is specified by the three variables of hue (dominant spectral color), value (brilliance), and chroma (saturation or purity), and written in the order and form: hue-value-chroma.


An isometric mineral, HgTe ; sphalerite group.

Colorado lapis lazuli

Dark blue lapis lazuli (lazurite) from the Sawatch Range, CO.

Colorado ruby

An incorrect name for the fiery-red garnet (pyrope) crystals obtained from Colorado.

Colorado topaz

True topaz of a brownish-yellow color obtained in Colorado, but quartz similarly colored is sometimes sold under the same name.

colored slates

Cambrian and Ordovician slates quarried in the vicinity of Granville, Washington County, NY. Colors include red, purple, green, and black. The slates are much used in decorative flooring.

color grade

The grade or classification into which a gem is placed by examination of its color in comparison to the color of other gems of the same variety.


An instrument for measuring and comparing the intensity of color of a compound for quantitative chemical analysis, usually based on the relationship between concentration of a chemical solution and the amount of absorption of certain characteristic colors of light.

colorimetric determination

An analytical procedure based on measurement, or comparison with standards, or color naturally present in samples or developed therein by the addition of reagents.

color index

In petrology, esp. in the classification of igneous rocks, a number that represents the percent, by volume, of dark-colored (i.e., mafic) minerals in a rock. According to this index, rocks may be divided into leucocratic (color index, 0 to 30), mesocratic (color index, 30 to 60), and melanocratic (color index, 60 to 100). Syn: color ratio.


Devoid of any color, as is pure water, a pane of ordinary window glass, or a fine diamond; therefore distinctly different from white, as in milk or white jade. As only transparent objects can be colorless, and no opaque object can be colorless, such terms as white sapphire and white topaz are misnomers. Rock crystal is a colorless variety of quartz; milky quartz is a white variety.

color ratio

See: color index.


a. The specks of gold seen after the successful operation of a gold pan, when finely crushed ore has been panned to remove the bulk of light minerals. The residual heavy fraction is then scanned for visual evidence of gold by the prospector.

b. In optical mineralogy, the colors of doubly refracting substances as seen in doubly polarized light (crossed polars). See also: birefringence.


A shovel used to stir lead ores during washing.


a. The mineral group ferrocolumbite, magnocolumbite, and manganocolumbite.

b. Standing alone it generally refers to ferrocolumbite, an orthorhombic mineral, FeNb (sub 2) O (sub 6) , in granites and pegmatites; an ore of niobium. Syn: niobite; dianite; greenlandite. CF: magnocolumbite.


See: niobium.


a. A round pillar set vertically or horizontally in a heading to support a machine drill.

b. The rising main or length of pipe conveying water from a mine to the surface. c. See: motive column. d. A solid core cut from a borehole. e. The drill-circulation liquid confined within a borehole. f. In borehole casing, a row of casing sections screwed together and forming a whole.


a. Composed of columnlike individuals.

b. A mineral with a form obscurely resembling prisms, e.g., hornblende. See also: prismatic. c. In columns produced by shrinkage joints, as in columnar basalt.

columnar charge

a. A charge of explosives in a blast hole in the form of a long continuous unbroken column.

b. A continuous charge in a quarry borehole. CF: deck charge.

columnar crystals

Elongated crystals that grew at right angles to a surface.

columnar jointing

Parallel, prismatic columns, polygonal in cross section, in basaltic flows and sometimes in other extrusive and intrusive rocks. It is formed as the result of contraction during cooling. Syn: columnar structure.

columnar section

A geologic illustration that shows in a graphic manner, and by use of conventional symbols for different rock types, the successive rock units that occur throughout a given area or at a specific locality. It may be accompanied by a very brief description of lithology and by appropriate brief notations indicating the thickness, age, and classification of the rocks. See also: geologic column.

columnar structure

a. A mineral fabric consisting of slender crystals of prismatic cross section, as in some amphiboles.

b. See: columnar jointing. c. Columns, 9 to 14 cm in diameter and 1 to 1.4 m in length, found in some calcareous shales or argillaceous limestones; oval to polygonal in section. Columns are perpendicular to bedding. Possibly a desiccation structure.

column flotation

a. A pneumatic flotation process with a counter-current flow of rising bubbles against settling ore within the flotation cell. Typically, the cell height is much greater than the cross section of the cell. The feed slurry is input above the midpoint of the column and water sprays are used at the top of the froth column to remove entrained hydrophilic particles from the froth.

b. Flotation carried out in a column machine utilizing countercurrent flow of air bubbles from the bottom and solid reagent-conditioned material from the top, such that tailings are withdrawn at the column bottom and the concentrate is collected over the column lip. There is no mechanical agitation.

column height

The length of each portion of a blast hole filled with explosive materials.

column leaching

Simulation of in-situ leaching through the use of a long narrow column in which ore sample and solution are in contact for measuring the effects of typical variables encountered in actual in-situ leach mining.

column load

A single continuous charge.

column of mud

See: mud column.

column of ore

A deposit of ore in a lode having a small lateral, but considerable vertical extent. An older term for ore shoot.

column pipe

The large cast-iron (or wooden) pipe through which the water is conveyed from the mine pumps to the surface. Syn: mounting pipe; rising main.


a. A variety of tetrahedrite containing 3.21% tin, from Japan.

b. An isometric mineral, Cu (sub 26) V (sub 2) (As,Sn,Sb) (sub 6) S (sub 32) ; in bronze-colored tetrahedra, from Butte, MT.