Appendix:Dictionary of Mining, Mineral, and Related Terms/E/1

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A concretionary nodule of clay ironstone about the size of a walnut that the ancients believed an eagle takes to her nest to facilitate egg-laying. Syn: aetite.


The inlet or intake of a fan.


A mineral, Ca (sub 3) (C (sub 6) H (sub 5) O (sub 7) ) (sub 2) .4H (sub 2) O ; forms as fine-grained nodules in sediments under the Weddell Sea off the Atlantic coast of Antarctica.

earth amber

a. Amber that is mined rather than from the sea. Also called earth stone.

b. Amber with its surface deteriorated in luster, transparency, and color.

earth auger

a. A hand-boring tool for testing clays, soils, or shallow deposits. See also: auger.

b. A dry-sampling device consisting of a helical-fluted rod encased by a cylindrical tube. The fluted rod is equipped with cutting edges, and the cuttings collect and are retained within the tube.

earth balsam

A variety of asphalt.

earth borer

An auger for boring into the ground, working in a cylindrical box to retain the cut earth until the tool is withdrawn.

earth current

A light electric current apparently traversing the Earth's surface but that in reality exists in a wire grounded at both ends, due to small potential differences between the two points at which the wire is grounded. Syn: telluric current.

earth dam

A dam constructed of earth material (such as gravel, broken weathered rock, sand, silt, or soil). It has a core of clay or other impervious material and a rock facing of riprap to protect against wave erosion.

earth drill

An auger.


Applied to conductors, connected to the general mass of earth in such a manner as will ensure at all times an immediate discharge of electrical energy without danger.

earthed system

Electrically, one with one neutral point or pole connected to earth.

earth fault

Electrical short circuit from live conductor to earth.

earth fault lockout system

An electrical system whereby a circuit is monitored to prevent application or restoration of supply if an earth fault exists.

earth fault meter

An instrument for measuring the insulation fault at low voltage without polarization. This instrument is more informative in checking detonators in loaded holes than the insulation meter.

earth fault protection

A system of protection designed to cause the supply to a circuit or system to be interrupted when the leakage current to earth exceeds a predetermined value. Also called earth leakage protection.

earth fault tester

An apparatus used to prevent or reduce current leakage to the ground when blasting in conducting orebodies, in wet shale or clay, and in underwater blasting, esp. in salt water. The apparatus has no battery and can be used when loading the hole to check if the conducting wires have become damaged during this operation. Syn: current leakage tester.

earth flax

An early name for fine silky asbestos. See also: amianthus.


A mass-movement landform and process characterized by downslope translation of soil and weathered rock over a discrete basal shear surface (landslide) within well-defined lateral boundaries. Little or no rotation of the slide mass occurs during displacement. Earthflows grade into mudflows with increasing fluidity. Also spelled: earth flow.

earth foam

A soft or earthy variety of calcite. See: aphrite.

earthing a conductor

Establishing an electrical connection between a conductor and the earth. An important safeguard in electrical installations.

earthing system

An electrical system in which all the conductors are earthed.

earth leakage protection

A protective system that operates as a result of leakage of current from electrical machines to earth. For electrical apparatus in mines, the usual method of leaking protection is known as the core balance system. This depends for its action on the balance of the currents in three phases. When a fault occurs, the balance is disturbed and the resulting magnetic effect in the transformer core induces a current in the secondary circuit, so energizing the tripping coil and operating the tripping mechanism on the circuit breaker. It may be operated by a leakage current as low as 5% of the full load current of the circuit.

earth pillar

See: hoodoo; pillar.


a. A local trembling, shaking, undulating, or sudden shock of the surface of the earth, sometimes accompanied by fissuring or by permanent change of level. Earthquakes are most common in volcanic regions, but often occur elsewhere. Syn: temblor.

b. Groups of elastic waves propagating in the earth, setup by a transient disturbance of the elastic equilibrium of a portion of the earth.

Earth's crust

See: crust.

Earth shell

See: shell.

earth slide

Downslope movement of part of an earth embankment sufficient to break up blocks and pulverize the material so that it moves in a somewhat fluid manner. CF: earth slump.

earth slope

The angle of superficial slope naturally assumed by rock debris, earthy detritus, etc., when piled up in mounds or ridges.

earth slump

Downslope movement of part of an earth embankment in blocklike masses without other apparent deformation. CF: earth slide.

earth stone

A term that may be applied to mined amber to distinguish it from sea amber. CF: earth amber.

earth wave

An obsolete syn. of seismic wave.

earth wax

See: ozocerite.


a. Consisting of minute particles loosely aggregated; claylike, dull.

b. In mineralogy, roughish to the touch, dull and lusterless. Porous aggregates of a mineral, such as the clays, scatter incident light so completely that they seem to be without luster and are described as dull or earthy. c. Composed of or resembling earth or soil; e.g., an "earthy limestone" containing argillaceous material and characterized by high porosity, loosely aggregated particles, and close association with chalk. d. Said of a type of fracture similar to that of a hard clay.

earthy breccia

A breccia in which rubble, sand, and silt plus clay each constitute more than 10% of the rock.

earthy fracture

A fracture resembling that of a lump of hard clay.

earthy lead ore

An earthy variety of cerussite.

earthy manganese

See: wad; bog manganese.


a. In surveying, an easement curve is a transitional curve.

b. An incorporeal right existing distinct from the ownership of the soil, consisting of a liberty, privilege, or use of another's land without profit or compensation; a right-of-way.


One of a number of holes surrounding a cut and fired immediately after it.

easer holes

Holes drilled around the cut to enlarge the cut area so that the trimmers may break out the ground to the required dimensions. The positioning and number of the easer holes will depend upon the pattern of the cut shots.

Eastman survey instrument

A particular make of mechanical and photographic borehole-drift indicators; the single-shot models are small enough to be used in EX diamond-drill holes. See also: drift indicator.

easy way

Scot. Easiest plane of splitting in granite, Aberdeenshire. CF: hard way.

eat out

a. N. of Eng. To turn a heading or holing to one side in order to mine the coal on the other side of a fault without altering the level course of the heading.

b. Said of a seam when the district or working place reaches a fault, or the boundary of old workings, or any other barren part of a mine.

ebb channel

Tidal channel in which the ebb currents are stronger than the flood currents.

ebb current

The movement of the tidal current away from shore or down a tidal stream.


Instrument for observing liquids' boiling point, esp. for determining a mixture's strength by the temperature at which it boils.

eccentric bit

A modified form of chisel used in drilling, in which one end of the cutting edge is extended further from the center of the bit than the other.

eccentric pattern

A mode of arranging diamonds set in the face of a bit in such a manner as to have rows of diamonds forming eccentric circles so that the path cut by each diamond slightly overlaps that of the adjacent stones. CF: concentric pattern.


A tetragonal mineral, Pb (sub 6) As (sub 2) O (sub 7) Cl (sub 4) .

echelon cell

Wedge-shaped glass cell used in absorption spectrography.

echelon pattern

A delay pattern that causes the true burden, at the time of detonation, to be formed at an oblique angle from the original free face.


A graphic recording of various sonic devices that shows ocean bottom profiles and delineates the bedding planes and dissimilar rock contacts to a depth of 1,500 ft (457 m) into the sediments.

echo sounder

In oceanography, a sounding apparatus using echo delay, for determining automatically the depth of sea beneath a ship.


A monoclinic mineral, Na (sub 3) (Mg,Fe) (sub 4) AlSi (sub 8) O (sub 22) (OH) (sub 2) ; amphibole group with Mg/(Mg + Fe (super 2+) ) = 0.5 to 1.0 and Fe (super 3+) /(Fe (super 3+) + Al) = 0 to 0.5; fibrous; in nepheline syenites; an asbestos mineral.


A coarse-grained, deep-seated ultramafic rock, consisting essentially of garnet (almandine-pyrope) and pyroxene (omphacite). Rutile, kyanite, and quartz are typically present.


The study of the relationships between organisms and their environment, including the study of communities, patterns of life, natural cycles, relationships of organisms to each other, biogeography, and population changes. Adj: ecologic; ecological. Syn: bionomics.

economic coal reserves

The reserves in coal seams that are believed to be workable with regard to thickness and depth. In most cases, a maximum depth of about 4,000 ft (1.2 km) is taken, and a minimum thickness of about 2 ft (0.6 m). The minimum economic thickness varies according to quality and workability. See also: thin seam.

economic depletion

The reduction in the value of a mineral deposit as the minerals reserves. See also: depletion.

economic geology

The study and analysis of geologic bodies and materials that can be utilized profitably by humans, including fuels, metals, nonmetallic minerals, and water; the application of geologic knowledge and theory to the search for and the understanding of mineral deposits.


An arrangement to preheat the feedwater before it enters the steam boiler. The water flows through a bank of tubes placed across the flue gases as they leave the boiler.


A dynamic community of biological organisms, including humans, and the physical environment with which they interact.


A circular movement of water. Eddies may be formed where currents pass obstructions or between two adjacent currents flowing counter to each other.

eddy-current brake

Arrangement by which internal currents are induced in a mass of metal as it moves relative to a magnetic field.

eddy-current testing

A nondestructive testing method in which eddy-current flow is induced in the test object. Changes in the flow caused by variations in the object are reflected into a nearby coil or coils for subsequent analysis by suitable instrumentation and techniques.


A German term for a shoot of precious-metal ore.


See: aedelforsite.


See: prehnite.


A monoclinic mineral, NaCa (sub 2) (Mg,Fe) (sub 5) Si (sub 7) AlO (sub 22) (OH) (sub 2) ; amphibole group with Mg/(Mg + Fe (super 2+) ) = 0.5 to 1.0; named for the type locality, Eden, NY.

edge dislocation

In a crystal, a row of atoms or ions marking the edge of a crystallographic plane extending only part way. CF: line defect.

edge seam mining

The working of steeply inclined coal seams, many features of which are comparable to metal mining. See also: stope.

edgewise conglomerate

A conglomerate exhibiting edgewise structure; e.g., an intraformational conglomerate containing elongated calcareous pebbles that are transverse to the bedding. See also: edgewise structure.

edgewise structure

A primary sedimentary structure characterized by an arrangement of flat, tabular, or disk-shaped fragments whose long axes are set at varying steep angles to the bedding. It may be due to running water or to sliding or slumping soon after deposition. See also: edgewise conglomerate.


See: prase; mother-of-pearl.


a. Titanic acid, rutile, occurring in golden-brown, orthorhombic crystals.

b. An early name for rutile.

eduction pipe

The exhaust pipe from the low-pressure cylinder to the condenser.

Edwards roaster

Furnace with series of horizontal stepped hearths each equipped with stirring rabbles. Used to sweet-roast or desulfurize pyritic concentrates, notably gold-bearing sulfides. Moist-to-wet feed progresses step by downward step, meeting hot gases produced toward discharge end from burning pyrite.

effective belt tension

That portion of the total tension in a conveyor belt effective in actually moving the loaded belt. It is often referred to as horsepower pull. Effective tension is the difference between tight side tension and slack side tension.

effective breaking force

A product of the weight, strength and the degree of packing, calculated per volume of a given drill hole.

effective diameter

a. The size of an excavation within its stress ring; it includes not only the actual hole in the rock but the destressed loose and semiloose rock that surrounds it.

b. Particle diameter corresponding to 10% finer on the grain-size curve. Also called effective size.

effective grounding

In mining, effective grounding means that the path to ground from circuits, equipment, or conductor enclosures is permanent and continuous and has carrying capacity ample to conduct safely any currents liable to be imposed upon it. The path to ground associated with high-voltage alternating-current systems will have impedance low enough to limit potential above ground to a maximum of 100 V during the flow of ground fault current and to facilitate operation of the circuit protective devices. On low-voltage systems the sustained voltage above ground, appearing on the frames of power utilizing equipment during existence of a ground fault, will not be greater than 35 V; except when ground circuit check systems requiring higher voltage are used, a maximum of 100 V for a duration of 0.2 s is permissible. When bonded or mechanically connected track is available, such track is considered the grounding medium for direct current equipment only.

effective permeability

A measure of the ability of a rock to transmit a given fluid when the rock contains more than one fluid.

effective piece weight

The weighted average weight of the pieces of sink material as found by separating a given coal product at any required specific gravity. Syn: piece weight.

effective pillar area

The area of solid coal within the fractured and crushed edges of the pillar.

effective porosity

a. The ratio of the volume of liquid that a given mass of saturated rock or soil will yield by gravity to the volume of that mass.

b. The property of rock or soil containing intercommunicating interstices, expressed as a percent of bulk volume occupied by such interstices. c. The ratio of the volume of the voids of a soil mass that can be drained by gravity to the total volume of the mass.

effective screen aperture

The cut point (equal errors or partition size) at which a screening process operates in dividing the material treated into two size fractions.

effective screening area

Total area of the apertures expressed as a percentage of the useful area of a screen. Syn: open area.

effective span

The distance between the centers of support, or the clear distance between supports plus the effective depth of the beam or slab, the lesser value being taken.

effective teeth

The number of sprocket teeth that engage the chain rollers during one revolution of the sprocket. Applies to sprockets for double-pitch roller chains.

effective temperature

A measure of warmth that is often employed to assess the health and comfort conditions of mine workings, which are a function of dry- and wet-bulb temperatures and air velocity. See also: dehumidification; dry kata cooling power.

effective unit weight

The unit weight of a soil that, when multiplied by the height of the overlying column of soil, yields the effective pressure due to the weight of the overburden. See also: unit weight.

efficiency engineer

A technical officer who examines processes, methods, and operations in a mine, mill, or smelter, and connecting links, with a view to their improvement of maintenance at an agreed operating standard.

efficiency of a rectifier

The ratio of the power output to the total power input.

efficiency of screening

The weight of underflow (excluding oversize) expressed as a percentage of the total weight of material below the reference size in the feed.

efficiency of separation

In coal washing this may be expressed as: Efficiency, percent = Actual yield of clean coal X 100 / Theoretical yield at the ash content of the clean coal. The efficiency of separation thus expresses as a percentage, that proportion of the float coal obtained by float-and-sink analysis that will be recovered in practice by a particular washer. The theoretical yield is derived by plotting the cumulative yield of the reconstituted feed coal against the appropriate cumulative ash content and reading off the yield corresponding to the ash content of the clean coal actually obtained. See also: washery.

efficiency of sizing

The weight of material correctly placed above or below the reference size, expressed as a percentage of the weight of corresponding material in the feed.

efficient airway size

For a given air quantity, the efficient airway size is that size for which the combined capital and operating cost is minimal.

efficient structure

A structure in which the load-bearing members are arranged in such a way that the weights and forces are transmitted to the foundations by the cheapest means consistent with safety and permanency.


a. A whitish fluffy or crystalline powder, produced as a surface encrustation on a rock or soil in an arid region by evaporation of water brought to the surface by capillary action or by loss of water of crystallization on exposure to the air. It may consist of one or several minerals, commonly soluble salts such as gypsum, calcite, natron, and halite. Syn: bloom.

b. The process by which an efflorescent salt or crust is formed.


In mineralogy, forming an incrustation or deposit of grains or powder that resembles lichens or dried leaves; not uncommonly due to loss of water of crystallization.


A liquid, solid, or gaseous product, frequently waste, discharged or emerging from a process.


a. The property of gases that allows them to pass through porous bodies; i.e., the flow of gases through larger holes than those to which diffusion is strictly applicable.

b. The emission of relatively fluid lava onto the Earth's surface; also, the rock so formed. CF: extrusion.


See: extrusive.


A Welsh term for copper.

egg coal

a. A particular size of anthracite coal that passes through 3-1/4-in to 3-in (8.26-cm to 7.62-cm) round holes and over 2-1/16-in (5.24-cm) round holes. See also: anthracite coal sizes.

b. A particular size of bituminous coal that passes through 4-in (10.2-cm) round holes and over 1-1/2-in (3.81-cm) round holes (sizes are not uniform but vary with the coalfield).


See: briquette.


See: oolite.


An isometric mineral, Hg (sub 6) Cl (sub 3) O(OH) or Hg (sub 4) Cl (sub 2) O ; forms brownish-yellow (darkening to black on exposure) dodecahedra with montroydite, calomel, and other mercury minerals at New Idria, CA, and Terlingua, TX.


A monoclinic(?) material, CaFe (sub 14) (PO (sub 4) ) (sub 10) (OH) (sub 14) .21H (sub 2) O(?) ; forms yellowish-brown nodules with fibrous lamellar structure embedded in clay with trona and thernardite in the Eguei#1. region of Chad and Sudan. (Not yet adequately described for a mineral species.)

Egyptian alabaster

Banded calcite from near Thebes, Egypt. See also: onyx marble.

Egyptian emerald

Emeralds from the ancient Egyptian mines of Jabal Sukayt and Jabal Zab-rah east of Aswan, in mica schist and talc schist.

Egyptian jasper

a. A banded jasper found as pebbles scattered over the surface of the Egyptian desert chiefly between Cairo and the Red Sea; used as a broochstone and for other ornamental purposes. Syn: Egyptian pebble.

b. Any jasper in which the colors run in zones.

Egyptian pebble

See: Egyptian jasper.

Egyptian peridot

Term properly applied only to peridot (olivine) from St. John's Island in the Red Sea.

Ehrhardt powder

Any of a series of explosive mixtures containing potassium chlorate, together with tannin, powdered nutgalls, or cream of tartar. Used for blasting, shells, etc.

Eichhorn-Liebig furnace

A handworked muffle furnace.


A multiple twin consisting of eight individuals. CF: cyclic twin; trilling; fourling; fiveling.

Eimco drill jumbo

Drills or drifters mounted on a horizontal drill bar supported by the rocker shovel of an Eimco loader.

eisener hut

Ger. Name for iron hat or gossan.


See: ferberite.


See: ferberite.


A trigonal mineral, Na (sub 2) Mg(CO (sub 3) ) (sub 2) ; associated with trona, nahcolite, or in places searlesite, from oil-well cores in northeastern Utah.


A tetragonal mineral, ThCa (sub 2) Si (sub 8) O (sub 20) ; radioactive; metamict; from the gem pits of Eheliyagoda, Raknapura district, Sri Lanka; as fine crystals at the Mont St. Hilare Quarry, PQ, Canada.


A term in Sri Lanka for a drain, as around a gem pit.


An alternative spelling of eleolite.


a. Capable of sustaining stress without permanent deformation; the term is also used to denote conformity to the law of stress-strain proportionality. An elastic stress or elastic strain is a stress or strain within the elastic limit.

b. A physical property of minerals that may be bent without losing cohesion and that return to their original shape when released, e.g., micas. CF: plastic; flexible.

elastic aftereffect

See: creep recovery.

elastic axis

The elastic axis of a beam is the line, lengthwise of the beam, along which transverse loads must be applied in order to produce bending only, with no torsion of the beam at any section. Strictly speaking, no such line exists except for a few conditions of loading. Usually the elastic axis is assumed to be the line that passes through the elastic center of every section. The term is most often used with reference to an airplane wing of either the shell or multiple-spar type. CF: torsional center; flexural center; elastic center.

elastic bitumen

See: elaterite.

elastic boundary

The boundary of an underground opening that requires no support. The material around this boundary may be considered to be in the elastic state, and no pressure need be exerted against the boundary to prevent the material from fracturing and falling into the opening.

elastic center

The elastic center of a given section of a beam is that point in the plane of the section lying midway between the flexural center and center of twist of that section. The three points may be identical and are usually assumed to be so. CF: flexural center; torsional center; elastic axis.

elastic deformation

Deformation of a substance, which disappears when the deforming forces are removed. Commonly, that type of deformation in which stress and strain are linearly related, according to Hooke's law. CF: plastic deformation.

elastic design

Design of a structure based on working stresses which are about one-half to two-thirds of the elastic limit of the material. For redundant frames, this method of design is replaced by the plastic design. See also: plastic design.

elastic discontinuity

A boundary between strata of different elastic moduli and/or density at which seismic waves are reflected and refracted.


The property or quality of being elastic; said of a body that returns to its original form or condition after a displacing force is removed. See also: elasticity of bulk; Hooke's law.

elasticity of bulk

a. The property possessed by all substances by which they tend to recover their original volume after being compressed or extended.

b. The elasticity for changes in the volume of a body caused by changes in the pressure acting on it. The bulk modulus is the ratio of the change in pressure to the fractional change in volume. See also: elasticity.

elastic limit

The greatest stress that can be developed in a material without permanent deformation remaining when the stress is released.

elastic mineral pitch

See: elaterite.

elastic modulus

See: modulus of elasticity.

elastic rebound

Elastic recovery from strain.

elastic surface waves

Waves that travel only on a free surface where the solid elastic materials transmitting them are bounded by air or water.

elastic zone

In explosion-formed crater nomenclature, the remote zone that undergoes no measurable permanent deformation.


A massive, amorphous, dark-brown metamorphic hydrocarbon ranging from soft and elastic to hard and brittle; melts in a candle flame without decrepitation; conchoidal fracture. Also called liverite. See also: coorongite; wurtzilite. Syn: elastic bitumen; elastic mineral pitch; mineral caoutchouc.


a. See: red schorl; rubellite; ilvaite.

b. A trigonal mineral, 3[Na(Li,Al) (sub 3) Al (sub 6) (OH,F) (sub 4) (BO (sub 3) ) (sub 3) Si (sub 6) O (sub 18) ] ; tourmaline group; occurs in triangular and hexagonal prisms; varicolored; commonly zoned, pyroelectric and piezoelectric; in granites and granite pegmatites; and used as a gemstone (pink rubellite, blue indicolite, green verdolite, colorless achroite, zoned pink-white-green watermelon tourmaline).

el conveyor

A trough-type roller or wheel conveyor consisting of two parallel rows of rolls or wheels set at a 90 degrees included angle, with one row providing a sloped carrying surface and the other acting as a guard. See also: roller conveyor; troughed roller conveyor; wheel conveyor.

El Doradoite

A trade name in El Dorado County, California, for a blue quartz that may be cut as a gemstone.

electric air drill

A type of tripod drill operated by compressed air supplied by a portable motor-driven compressor that accompanies the drill.

electrical conductivity

A measure of the ease with which a conduction current can be caused to flow through a material under the influence of an applied electric field. It is the reciprocal of resistivity and is measured in mhos per meter.

electrical double layer

Helmholtz layer. Zone that surrounds a particle in aqueous suspension or other electrolyte. Transition zone between the monomolecular zone of shear immediately coupled ionically to the discontinuity lattice at the particle's surface and the normal aqueous phase that exists from 50 to 5,000 Aa and beyond. This zone of change contains a superconcentration of ions drawn from the normal population of the liquid phase. See also: zeta potential.

electrical engineer

An engineer in charge of all electrical plant and associated labor at a mine or colliery. He or she has an assistant in charge of all the underground electrical equipment, operations, and labor. The electrical engineer is under the authority of the colliery manager.

electrical method

A geophysical prospecting method that depends on the electrical or electrochemical properties of rocks. The resistivity, spontaneous-polarization, induced-polarization, and inductive-electromagnetic methods are the principal electrical methods.

electrical plan

A plan, drawn to the same scale as the working plan, that shows the position of all electrical apparatus installed underground except signals and telephones.

electrical precipitation

The removal of suspended particles from gases by the aid of electrical discharges, using alternating or direct current. Alternating current agglomerates the suspended particles into larger aggregates, causing rapid settling, esp. if the gases are quiescent. Direct current is used when large volumes of rapidly moving gas, such as occur in smelter flues, are treated. The suspended particles within a strong electric field of constant polarity become charged and are then attracted to a plate (electrode) of opposite charge.

electrical prospecting

Prospecting that makes use of three fundamental properties of rocks. One is the resistivity, or inverse conductivity. This governs the amount of current that passes through the rock when a specified potential difference is applied. Another is the electrochemical activity with respect to electrolytes in the ground. This is the basis of the self-potential method. The third is the dielectric constant. This gives information on the capacity of a rock material to store electric charge, and it must be taken into consideration when high-frequency alternating currents are introduced into the earth, as in inductive prospecting techniques. Electrical methods are more frequently used in searching for metals and minerals than in exploring for petroleum, mainly because most of them have proved effective only for shallow explorations.

electrical protection

Protection is provided by fuses or other suitable automatic circuit-interrupting devices for preventing damage to circuits, equipment, and personnel by abnormal conditions, such as overcurrent, high or low voltage, and single phasing.

electrical puncturing

A rock fracturing technique, applied to secondary fragmentation in quarries, that is characterized by an almost instantaneous action and is accompanied by a mechanical weakening of the dielectric and a lowering of the resistance of the puncture path. If, after puncturing, a high-frequency current continues to pass between the contacts, the action of the conduction current and electric field will rapidly heat the rock, leading to thermal puncture, in which the dielectric is transformed into a good conductor along the puncture path. Further intensive heating will give rise to thermal stresses sufficient to fracture the rock.

electrical resistance inclinometer

An instrument to indicate when a long hole in a coal seam is deviating into the roof or floor. It may be used in underground gasification and pulsed-infusion shotfiring. It uses, among other things, a pellet of mercury to indicate the gradient by its position along a tube.

electrical resistance strain gage

An appliance for measuring strain that may be employed in roof-control research. It makes use of the change in electrical resistance of a thin wire when stretched under the influence of strata strain. Syn: resistance strain gage. See also: acoustic-strain gage; mechanical extensometer.

electrical rock fracture

A rock-fracturing technique in which electrical energy is used directly in fracturing the rock, either by heating it in a variable electric or electromagnetic field set up in the rock by a high-frequency electric current, or by the direct puncturing of the rock by an electric current.

electrical slate

Slate principally of the mica variety. It should have high mechanical and dielectric strength, be readily machinable, and have low porosity.

electrical twinning

A type of quartz twinning in which the two or more intergrown parts are related as by a rotation of 180 degrees about the common Z = c axis. The separate individuals of the twin are either all right handed or all left handed. Electrical twinning cannot be detected by optical tests, but can be recognized by etching, X-ray study, pyroelectric tests, or the distribution of the x 5161 or s 1121 faces. Syn: Dauphine twinning; orientational twinning.

electrical well logging

The process of recording the formations traversed by a drill hole, based on the measurements of two basic parameters observable in uncased holes; namely, the spontaneous potential and the resistivity of the formations to the flow of electric currents. The detailed study in situ of the formations penetrated by a drill hole, based on measurements made systematically by lowering an apparatus in the hole responding to the following physical factors or parameters: (1) the resistivities of the rocks; (2) their porosity; (3) their electrical anisotropy; (4) their temperature; and (5) the resistivity of the drilling muds.

electric blasting

The firing of one or more charges electrically, whether electric blasting caps, electric squibs, or other electric igniting or exploding devices are used.

electric blasting cap

a. A device for detonating charges of explosives electrically. It consists essentially of a blasting cap, into the charge of which a fine platinum wire is stretched across two protruding copper wires, the whole fastened in place by a crimp or plug. The heating of the platinum wire bridge by the electric current ignites the explosive charge in the cap, which in turn detonates the high explosive.

b. Detonator fired electrically. See also: electric detonator.

electric braking

A system in which a braking action is applied to an electric motor by causing it to act as a generator.

electric cable

The conducting wires through which an electric current is conveyed to points in and about a mine, where it is required for lighting or motive power. See also: armored cable.

electric calamine

Zinc silicate or calamine; so called on account of its strong pyroelectric properties, and to distinguish it from smithsonite. See also: calamine.

electric cap lamp

This lamp consists of a flat portable battery that is strapped around the miner's waist and is connected by an insulated cord to a small electric light and reflector that is fastened on the front of the miner's cap. See also: safety lamp.

electric coal cutter

A coal cutter operated by an electric motor; used in coal mines.

electric coal drill

An electric motor-driven drill designed for drilling holes in coal for placing blasting charges. Syn: coal drill.

electric detonator

A detonator requiring electrical energy to activate the explosive train, detonating the base charge. See also: blasting cap; electric blasting cap.

electric ear

System used to control grinding rate in a ball mill; a microphone listens to the grinding sound and maintains this by varying the rate of new feed to the mill.

electric-eye method

A method of finding large diamonds in which the dry crushed ore is passed in a thin layer on a moving belt through a band of intense polarized light, which, if reflected from a large diamond, actuates a photoelectric cell, which calls attention to the large diamond.

electric furnace

A furnace using electricity to supply heat.

electric fuse

A metallic cup, usually containing fulminating mercury, in which are fixed two insulated conducting wires held by a plug, the latter holding the ends of the wires near to but not touching each other. At this plug is a small amount of a sensitive priming. When an electric current is sent from the battery through these conductors, the resulting spark fires the priming, then the fulminate and the charge of the explosive proper.

electric gathering mine locomotive

An electric mine locomotive, the chief function of which is to move empty cars into, and to remove loaded cars from, the working places. Syn: gathering locomotive; gathering mine locomotive. See also: gathering motor.

electric haulage mine locomotive

An electric mine locomotive used for hauling trains of cars, which have been gathered from the working faces of the mine, to the point of delivery of the cars.

electric hoist

See: electric winder.

electric-hoist man

See: hoistman.

electric ingot process

A continuous method of melting and casting metal with progressive solidification. The molten metal is completely protected from the atmosphere. There is minimum segregation, and as no refractory linings are used, there is no contamination. Sound ingots with high yield and no pipe are produced, and as the method possesses extreme flexibility it is possible to make small as well as relatively large ingots.

electric lamp

See: cap lamp; hand electric lamp.

electric log

The generic term for a well log that displays electrical measurements of induced current flow (resistivity log, induction log) or natural potentials (spontaneous-potential curve) in the rocks of an uncased borehole. An electric log typically consists of the spontaneous-potential curve and one or more resistivity or induction curves. The Archie equations form the basis for interpretation of electric logs. Abbrev: E-log. Informal syn: resistivity log. See also: borehole log; well logging.

electric logging

a. A technique in which electrical measurements are made, and recorded at the surface, while a series of electrodes or coils is caused to traverse a borehole. The resulting curves can be used for geological correlation, and, under favorable circumstances, for the recognition of some rock properties and for indicating the nature and amount of the fluids in the pores of the rock.

b. The act or process of taking resistivity, porosity, electrical anisotropy, etc., measurements in a borehole using an electromagnetic teleclinometer or other electrode device. Also called electrical logging. See also: self-potential log.

electric master fuse

See: multifuse igniter.

electric mine locomotive

An electric locomotive designed for use underground. See also: locomotive; mine locomotive; electric haulage mine locomotive; electric permissible mine locomotive; electric gathering mine locomotive.

electric mule

Electric motor.

electric permissible mine locomotive

An electric locomotive carrying the official approval plate of the U.S. Mine Safety and Health Administration.

electric powder fuses

These fuses were designed so that electrical shotfiring methods could be used for initiating blasting powder. The powder fuse consists of a thick paper tube containing a small charge of blasting powder, with an ordinary low-tension fusehead fixed at one end. On passing electric current through the fusehead, it flashes and sets off the blasting powder in the tube, which can then initiate the main charge of blasting powder in the shot hole.

electric precipitation

A method of collecting particulate particles used chiefly in air polution control that consists of inducing an electric charge on the dust particles and collecting them on an oppositely charged device.

electric prospecting instruments

Geophysical prospecting instruments that measure the electrical characteristics of rocks.

electric resistance

The opposition of an electric circuit to the flow of current.

electric resistance strain gage

This gage consists essentially of a grid of fine wire cemented to a paper membrane, which can be attached to the surface under investigation. The ends of the wire grid are spot welded to a metal strip for the terminal connections. The use of these gages depends upon the fact that certain alloys show a linear relationship between applied strain and electrical resistance, so that if a wire constructed from one of these alloys is fixed to the surface of an object subject to variable strain, the change of resistance in the wire will be a measure of the change of strain in the object.

electric rotary drill

A hand-held rotary drill driven by an electric motor, which may be used in rock or coal. It may be of fan-cooled design with several rod speeds to suit different rocks. The use of aluminum or aluminum alloys is not favored where methane is liable to be present. This drill produces considerably less dust than the percussive drill.

electric shock

Paralysis of the nerve center that controls breathing or a regular heartbeat. Some symptoms of electric shock are sudden loss of consciousness, absence of respiration or respiration that cannot be detected, weak pulse, and burns.

electric shovel

Most of the larger modern machines are electrically driven and are equipped with the Ward-Leonard system of control, which allows alternating current of fairly high voltage to be carried to the shovel over a very flexible electric cable. This cable is usually carried on a sled back of the shovel or on a reel on the shovel base. The current drives an alternating current motor, which is connected to, and drives, direct current generators, one for each of the operations of the shovel, and an exciter. Each direct current generator and the direct current motor which it drives are in a closed circuit. The field in each circuit is regulated by magnetic contactors or by rotating controls actuated by master controllers at the operator's position.

electric-shovel craneman

See: shovel craneman.

electric slope engineer

In bituminous coal mining, one who operates a hoist powered by electricity to haul loaded and empty cars along a haulage slope to surface of mine.

electric sponge

An electric centrifugal pump consisting of a small vertical centrifugal pump so designed that it will draw water if it is only 2 to 3 in (5.1 to 7.6 cm) deep. It is placed in the water at the bottom of a shaft and lifts the water up to a horizontal centrifugal pump placed about 50 ft (15.2 m) above.

electric squib

A small shell containing an explosive compound that is ignited by the electric current brought in through the lead wires. Used for firing single small holes loaded with black powder.

electric steel

Steel made in an electric furnace.

electric traction

The haulage of vehicles by electric power, derived from overhead wires, third rail, storage batteries, or diesel-driven generators mounted on the vehicles.

electric wheel

A wheel containing the motor and all the required gearing so that it is an independent drive unit.

electric winder

A winder or hoist driven by an electric motor.

electroacoustic transducer

A transducer for receiving waves from an electric system and delivering waves to an acoustic system or vice versa.

electrocast process

A method of producing refractory materials in the desired form by mixing the raw materials in the requisite proportions, heating to fusion in an electric furnace, and then casting.


Chemical action employing a current of electricity to cause or to sustain the action.

electrochemical corrosion

Corrosion that occurs when current flows between cathodic and anodic areas on metallic surfaces.

electrochemical equivalent

The weight of an element, compound, radical, or ion involved in a specified electrochemical reaction during the passage of a unit quantity of electricity, such as a faraday, an ampere-hour, or a coulomb.

electrochemical series

See: electromotive force series.


a. In arc welding, a current-carrying rod that supports the arc between the rod and work, or between two rods as in twin carbon-arc welding. It may or may not furnish filler metal.

b. In resistance welding, a part of a resistance welding machine through which current and, in most cases, pressure are applied directly to the work. The electrode may be in the form of a rotating wheel, rotating roll, bar, cylinder, plate, clamp, chuck, or modification thereof. c. A conductor (as a metallic substance or carbon) used to establish electrical contact with a nometallic portion of a circuit (as in an electrolytic cell, a storage battery, an electron tube, or an arc lamp). See also: anode; cathode.

electrode burnoff rate

The rate at which an electrode is consumed by an arc in units of mass per time per arc power.

electrode configuration

Pattern in which the electrodes are set up.

electrode consumption rate

The rate at which an electrode is consumed by an arc in units of mass per time per arc current.

electrode melting rate

The rate at which an electrode is consumed by an arc in units of mass per time.


The deposition of a substance upon an electrode by passing electric current through an electrolyte. Electroplating (plating), electroforming, electrorefining, and electrowinning result from electrodeposition. Syn: electrolytic deposition.

electrode potential

a. The potential difference at the surface of separation between the electronic and electrolytic conductors that make up the electrode. In the terminology of corrosion it is sometimes called the open-circuit potential.

b. The potential of a half-cell as measured against a standard reference half-cell.

electrode spacing

Distance between successive electrodes.


Dialysis assisted by the application of an electric potential across the semipermeable membrane. Two important uses of electrodialysis are in water desalination and in removing electrolytes from naturally occurring colloids such as proteins. CF: electro-osmosis.


The movement of fluids through porous diaphragms caused by the application of an electric potential.


The application of electrolysis to recover metal from its salts. Syn: electrowinning.


The electromotive force set up between the two sides of the sheet when an electrolyte is forced through a sheet of some pervious solid dielectric. This electromotive force is proportional to the pressure and to the electrical resistivity of the liquid, and inversely proportional to its viscosity.

electrofiltration potential

An electrical potential that is caused by movement of fluids through porous formations. Syn: streaming potential; electrokinetic potential.


The electroplating of zinc upon iron or steel.

electrokinetic potential

See: electrofiltration potential; zeta potential.


A method of breaking down a compound in its natural form or in solution by passing an electric current through it, the ions present moving to one electrode or the other where they may be released as new substances.


a. A nonmetallic electric conductor (as a solution, liquid, or fused solid) in which current is carried by the movement of ions instead of electrons with the liberation of matter at the electrodes; a liquid ionic conductor.

b. A substance (as an acid, base, or salt) that, when dissolved in a suitable solvent (as water) or when fused, becomes an ionic conductor. c. For ceramic applications, an electrolyte is a substance capable of dissociating partly or completely into ions in water. For clay dispersions, the basic electrolytes promote deflocculation while the acidic electrolytes produce the opposite effect, flocculation.

electrolytic copper

Copper that has been refined by electrolytic deposition, including cathodes, which are the direct product of the refining operation; refinery shapes cast from melted cathodes; and, by extension, fabricators' products made therefrom. Usually when this term is used alone, it refers to electrolytic tough pitch copper without elements other than oxygen being present in significant amounts.

electrolytic deposition

The production of a metal from a solution containing its salts by the passage of an electric current through the solution. In electrorefining, the operation is carried out in an electrolytic cell in which the metal is deposited upon the cathode or starting sheet. See also: electrodeposition.

electrolytic dissociation

Dissociation in a solvent of molecules of the dissolving substance as cations and anions. Syn: ionization.

electrolytic dissolusion

The act or process of dissolving the diamond matrix metal in the crown of a bit utilizing the chemical decompositional effects of a direct electrical current on a metal object submerged in an acidic solution.

electrolytic iron

A very pure iron produced by an electrolytic process. It has excellent magnetic properties and is often used in magnet cores.

electrolytic lead

Lead refined by the Betts process; it has purity of about 99.995% to 99.998% lead.

electrolytic polishing

Producing a smooth bright surface on metal by immersion as an anode in an electrolytic bath.

electrolytic process

a. A process employing the electric current for separating and depositing metals from solution.

b. As used by the diamond-bit-setting industry, the process in which the chemical decompositional effects of subjecting metal objects immersed in an acidic solution to a flow of direct electric current is utilized to dissolve the metal in the crown of a worn diamond bit to free and salvage the diamonds.

electrolytic reduction

Removal of oxygen (or decrease of its active valency in the case of a positive element) by electrical means.

electrolytic refining

Suspension of suitably shaped metal ingots as anodes in an electrolytic bath, alternated with sheets of the same metal in a refined state or inert metal, which act as starters or cathodes. Impurities remaining on the anodes are detached as anode slime or are dissolved in the electrolyte from which they must be systematically removed (stripped).


The extraction and refining of metals by the use of electric currents.

electrolytic zinc

Zinc exceeding 99.9% purity, produced by electrodeposition.


To decompose a compound, either liquid, molten, or in solution, by an electric current.

electromagnetic brake

One in which rubbing surfaces are pressed together when electric current is passed through a solenoid; also, a braking system that uses magnetic attraction generated by an electromagnet as a braking force.

electromagnetic damping

Commonly found in seismometers of the induction type. It may be used in mechanical seismographs by employing a copper plate moving between two permanent magnets. Induction seismometers depend upon voltage generated by motion of coil in the magnetic field.

electromagnetic detector

An instrument used in aerial geophysical prospecting for the direct detection of conducting ores. An alternating electromagnetic field is transmitted from an aircraft. This field is received by the conducting body in the Earth and reradiated with some change in phase. The resultant field is picked up by the device, towed behind the aircraft, and compared with the transmitted field. The phase shift is measured automatically and recorded as a profile during flight. See also: geophysical exploration.

electromagnetic geophone

The simplest, most widely used type of geophone. It consists of a coil and a magnet, one rigidly fixed with respect to the Earth and the other suspended from a fixed support by a spring. Any relative motion between the coil and magnet produces an electromotive force across the coil's terminals that is proportional to the velocity of the motion.

electromagnetic methods

Group of electrical exploration methods in which one determines the magnetic field that is associated with the electrical current through the ground.

electromagnetic prospecting

A geophysical method employing the generation of electromagnetic waves at the Earth's surface; when the waves penetrate the Earth and impinge on a conducting formation or orebody, they induce currents in the conductors, which are the source of new waves radiated from the conductors and detected by instruments at the surface.

electromagnetic separation

A process of removing magnetic materials from relatively nonmagnetic materials, using electromagnets which travel along a conveyor, over a drum, or into a revolving screen. See also: electrostatic separator; tramp iron.

electromagnetic spectrum

The entire range of electrical energy, extending from the extremely long radio rays at one end to the extremely short X-rays at the other. The visible spectrum (visible light) is included.

electromagnetic surveying

The act or process of using a geophysical method of systematically measuring electromagnetic waves in a specific area of the Earth's surface or in an area adjacent to boreholes. See also: electromagnetic prospecting.


The totality of electric and magnetic phenomena, or their study; particularly those phenomena with both electric and magnetic aspects, such as electromagnetic induction.


A term covering the various electrical processes for the industrial working of metals; e.g., electrodeposition, electrorefining, and operations in electric furnaces.

electromotive force series

The elements can be listed according to their standard electrode potentials. The more negative the potential, the greater the tendency of the metals to corrode but not necessarily at higher rates. This series is useful in studies of thermodynamic properties. A hydrogen gas electrode is the standard reference and is placed equal to zero. All potentials are positive or negative with respect to the hydrogen electrode. Also known as the emf series. Syn: electrochemical series.


One of the constituent elementary particles of an atom. A charge of negative electricity equal to about 1.602 X 10 (super -19) C and having a mass when at rest of about 9.107 X 10 (super -28) g or 1/1,837 that of a proton. Electrons surround the positively charged nucleus of the atom and determine the chemical properties of the atom.

electron beam melting

A melting process in which heat is supplied by a beam of electrons directed at the metal in high vacuum.

electron capture

A mode of radioactive decay in which an orbital electron is captured by the nucleus. The resulting nuclear transformation is identical with that in beta (super +) emission.


Descriptive of element or group that ionizes negatively, or acquires electrons and therefore becomes negatively charged anion.

electronic CO detector

A portable, lightweight instrument for detecting carbon monoxide in mine air. Most of these instruments allow instantaneous reading of the carbon monoxide content but can also be used in an automated recording and monitoring system.

electronic filter

An air cleaner in which particulate matter in the airstream is electrically charged, then attracted to surfaces oppositely charged.

electronic high-level indicator

An electronic device that signals an operator when a bin is filled to capacity.

electronic liquid density instrument

A glass float on the end of a thin rod suspended in a liquid which is supported by two flat springs so that it is constrained to precise vertical motion. The float-rod assembly carries a coil similar to the voice-coil of a dynamic loudspeaker and a differential transformer core. Vertical movement of the float is detected by the electrical response of the differential transformer. The coil moves in a strong, radial, magnetic field, and when the float is buoyed up by the liquid, the reaction force between the coil and the field is used to pull it down. Thus, balance is achieved at a null position by adjusting the coil current while observing the null indicator.

electronic microscope

An instrument similar to the ordinary light microscope, but producing a much magnified image, which is received on a fluorescent screen and is recorded by using a camera. Instead of a beam of light to illuminate the material, a parallel beam of electrons is used. Its magnification is up to about 100,000 times.


The utilization based on the phenomena of conduction of electricity in a vacuum (thermionic valves), in a gas (thyratrons), and in semiconductors (transistors).

electronic sentry

A device for mounting on any direct-current mobile mining machine that receives its power through a portable cable. The device cuts off the power from the machine and its trailing cable in the event of a ground fault, short circuit, or break in the cable, and prevents electrical flow as long as the trouble exists.

electronic sorting

See: LaPointe picker.

electronic tramp iron detector

An appliance to prevent large pieces of tramp iron from entering a primary breaker when the ore feed is by conveyor. The appliance is straddled across the conveyor and when the tramp metal (magnetic or nonmagnetic) of dangerous size passes under the detector it automatically stops the conveyor and sounds an alarm, and will not restart motion until the tramp material is removed.

electronic weighing

See: weighing-in-motion system.


The motion of liquid through a membrane under the influence of an applied electric field. See also: osmosis; thermo-osmosis.


a. Movement of colloid particles toward an oppositely charged electrode through a solution.

b. The movement toward electrodes of suspended charged particles in a fluid by applying an electromotive force to the electrodes that are in contact with the suspension. See also: cataphoresis.


To plate with an adherent continuous coating by electrodeposition; esp., to plate with a metal.


Electrodepositing metal (may be an alloy) in an adherent form upon an object serving as a cathode.

electropneumatic lighting

A method of lighting in which the well glass surrounding the bulb is flushed out with compressed air through a special valve before a self-contained generator commences to run; afterwards the exhaust from the turbine is passed through the lamp fitting with a small back pressure of 1-1/2 to 2 psi (10.3 to 13.8 kPa), preventing ingress of methane. The equipment can be used underground where the use of electricity is prohibited and for both roadway and face lighting.


a. Positively charged; having more protons than electrons. An electropositive ion is a cation.

b. Term used to describe substances that tend to pass to the cathode in electrolysis.


The process of anodically dissolving a metal from an impure anode and depositing it in a purer state at the cathode.


Any of various instruments for detecting the presence of an electric charge on a body, for determining whether the charge is positive or negative, or for indicating and measuring the intensity of radiation by means of the motion imparted to charged bodies (as strips of gold leaf) suspended from a metal conductor within an insulated chamber.

electrostatic capacity

Quantity of electricity needed to raise system one unit of potential.

electrostatic cleaning process

A method of cleaning small sizes of coal, namely, 0.1 to 2 mm, by passing the material over a slowly rotating roller through a high-voltage electrostatic field between the earthed roller and an adjacent wire. Coal loses its charge very slowly and is carried further around by the roller than the impurities, thus effecting separation with reasonable efficiency.

electrostatic precipitator

The most efficient of the dust samplers, the electrostatic precipitator is a medium-volume instrument. Air is drawn through a metal tube serving as a collecting surface (the anode) in which a platinum wire mounted axially acts as the ionizing and precipitating electrode (the cathode). A potential of about 10,000 V direct current is maintained across the tube and wire. The assembly mounting and collecting tube contains a small fan to induce air flow.


Science of electric charges captured by bodies that then acquire special characteristics because of their retention of such charges. Electrostatic bunching is particle cling during the laboratory screening of dry material in which frictional electric charge is set up.

electrostatic separation

A method of separating materials by dropping feed material between two electrodes, positive and negative, rotating in opposite directions. Nonrepelled materials drop in a vertical plane; susceptible materials are deposited in a forward position somewhat removed from the vertical plane.

electrostatic separator

A vessel fitted with positively and negatively charged conductors that may be used for extracting dust from flue gas or for separating mineral dust from gangues.

electrostatic strength

As applied to electric blasting caps, a measure of the detonator's ability to withstand electrostatic discharges without exploding.


A trade name for a precise electronic surveying device that transmits a radio-frequency signal to a responder unit, which in turn transmits the signal back to the interrogator unit. The time lapse between original transmission and receipt of return signal is measured and displayed in a direct digital readout for eventual reduction to a precise linear distance. It operates on the same principle as the tellurometer. See also: tellurometer.


An electrochemical process in which a metal dissolved within an electrolyte is plated onto an electrode. Used to recover metals such as cobalt, copper, gold, and nickel from solution in the leaching of ores, concentrates, precipitates, matte, etc.


a. A part of the series isometric native gold-silver (Au-Ag); deep to pale yellow; argentiferous gold containing more than 20% silver. Also spelled elektrum. Syn: gold argentide.

b. An ancient Greek name, now obsolete, for amber. Also spelled elektron.

electrum metal

An alloy of gold and silver; contains from 55% to 88% gold.


a. A substance that cannot be decomposed into other substances.

b. A substance all of whose atoms have the same atomic number. The first definition was accepted until the discovery of radioactivity (1896), and is still useful in a qualitative sense. It is no longer strictly correct, because (1) the natural radioactive decay involves the decomposition of one element into others, (2) one element may be converted into another by bombardment with high-speed particles, and (3) an element can be separated into its isotopes. The second definition is accurate, but has the disadvantage that it has little relevance to ordinary chemical reactions or to geologic processes. c. In crystallography, any point, line, or plane about which crystal structure, crystal faces, or crystal symmetry, including translation, is symmetrically arrayed. CF: operation.

elementary particle

Applied to any particle that cannot be further subdivided.


A dark, translucent massive or coarsely crystalline variety of nepheline; greasy luster; may be used as an ornamental stone. Also spelled: elaeolite; elaolite.

eleolite syenite

See: nepheline syenite.

elevating conveyor

Any conveyor used to discharge material at a point higher than that at which it was received. Term is specific. applied to certain underground mine conveyors.

elevating grader

A grader equipped with a collecting device and elevator, by which the loosened material can be loaded to spoil banks or into vehicles for transport. See also: belt loader.


A general term for a topographic feature of any size that rises above the adjacent land or the surrounding ocean bottom; a place or station that is elevated. The vertical distance from a datum (usually mean sea level) to a point or object on the Earth's surface; esp. the height of a ground point above the level of the sea. The term is used synonymously with altitude in referring to distance above sea level, but in modern surveying practice the term elevation is preferred to indicate heights on the Earth's surface, whereas altitude is used to indicate the heights of points in space above the Earth's surface.

elevation correction

In gravity measurements, the corrections applied to observed gravity values because of differences of station elevation to reduce them to an arbitrary reference or datum level, usually sea level. The corrections consist of (1) the free-air correction, to take care of the vertical decrease of gravity with increase of elevation, and (2) the Bouguer correction, to take care of the attraction of the material between the reference datum and that of the individual station. In seismic measurements, the corrections are applied to observed reflection time values due to differences of station elevation in order to reduce the observations to an arbitrary reference datum or fiducial plane.


a. An apparatus used to facilitate the removal of coal from shuttle cars or low conveyors into mine cars.

b. A type of conveyor for raising coal, stone, ore, or slurry, usually at the coal preparation plant or mill. Normally it comprises a series of steel buckets attached to an endless chain. See also: bucket elevator. c. A cage hoist. d. A device for raising or lowering tubing, casing, or drive pipe, from or into well. e. An endless belt or chain conveyor with cleats, scoops, or buckets for raising material. f. A cage or platform and its hoisting machinery, as in a building or mine, for conveying persons or goods to or from different levels. See also: hoist. g. A vertical or steeply inclined conveyor. h. A machine that raises material on a belt or a chain of small buckets. i. A hinged circle or latch block provided with long links to hang on a hoistlike hook and used to hoist collared pipe, drill pipe and/or casing, and drill rods provided with elevator plugs. Some large elevators are fitted with slips for use on uncollared or flush-outside tubular equipment. j. A term sometimes and incorrectly used as a syn. of lifting bail. See also: hydraulic dredge; vertical reciprocating conveyor. k. An apparatus used to facilitate the removal of coal from shuttle cars or low conveyors into mine cars.

elevator bucket

A vessel generally rectangular in plan and having a back suitably shaped for attachment to a chain or belt and a bottom or front designed to permit discharge of material as the bucket passes over the head wheel of a bucket elevator.

elevator dredger

A dredger fitted with a bucket ladder.

elevator plug

A short steel plug provided with a pin thread by means of which it may be coupled to the upper end of a stand of drill rods. Its diameter is greater than that of the drill rod to which it is attached, and hence it provides a shoulder that can be grasped by an elevator. When each stand of rod is provided with an elevator plug and an elevator is used in lieu of a rod-hoisting plug, the handling of rods is facilitated and a round trip can be made in less time. Syn: rod plug.

elevator rope

A rope used to operate an elevator.

Elie ruby

A small-grained variety of pyrope garnet in the trap tuff of Kincraig Point, near Elie, Fife, Scotland.


a. To liquate; smelt.

b. To part by liquation.


A name applied to a subgroup of pyrobitumens rich in oxygen and partly soluble in alkali. They resemble an earthy brown coal and probably represent a product of intense weathering of bitumens.


A hexagonal mineral, Ca (sub 5) (SiO (sub 4) ,PO (sub 4) ,SO (sub 4) ) (sub 3) (F,OH,Cl) ; apatite group; it is chlorellestadite if (Cl>OH,F), fluorellestadite if (F>OH,Cl), or hydroxylellestadite if (OH>F,Cl). Hydroxylellestadite occurs as veinlets in blue calcite associated with wilkeite, idocrase, and similar contact metamorphic minerals at Crestmore, Riverside County, CA.

elliptical polarization

In optics, elliptically polarized light consisting of upward-spiraling vibration vectors, the surface of which is elliptical rather than circular, as in circular polarization. It is caused by the inconstant lengths of vibration vectors of mutually perpendicular plane-polarized waves whose path differences differ in phase by amounts other than (n+1)/4lambda on emergence from a crystal.

Elmore jig

A plunger-type jig of either single or mulitple compartments. Its distinguishing features are (1) an automatic control in the form of a cylinder that measures the specific gravity of the mixture of coal and refuse; (2) the refuse draw is a star gate under the overflow lip in each compartment, which extends the full width of the jig; and (3) the hutch is commonly collected with a screw conveyor and discharged through the refuse elevator. Used both for treatment of nut and slack sizes of bituminous coal.


An isometric mineral, K (sub 2) NaAlF (sub 6) ; associated with pachnolite in cryolite-bearing pegmatites of the Pikes Peak region, El Paso County, CO.


An orthorhombic mineral, Na (sub 2) ZrSi (sub 6) O (sub 15) .3H (sub 2) O; in fibrous, columnar, prismatic crystals in albitized nepheline-syenite pegmatites at Narsarsuk, Greenland; Kola Peninsula, Russia; Mont St. Hilare, PQ, Canada; and Tarbagatai, Kazakhstan.

Elsner's equation

In dissolution of gold by dilute aerated cyanide solution this reads: 4Au + 8NaCN + O (sub 2) + 2H (sub 2) O = 4NaAU(CN) (sub 2+4) NaOH . Analogous equation is given for silver. Other mechanisms have been suggested by Janin and Bodlaender, the latter requiring two stages of reaction with the intermediate formation of hydrogen peroxide. See also: MacArthur and Forest cyanide process.

Eltran method

Electrical exploration method in which an electrical transient is sent into the Earth and the change in shape of this transient is studied.


Liquid used to displace captured ions from the zeolite or resin on which they are held; also, in ion exchange processes, solution used for elution. In chromatography, the solution used to displace absorbed substances.


a. A method of mechanical analysis of a sediment, in which the finer, lightweight particles are separated from the coarser, heavy particles by means of a slowly rising current of air or water of known and controlled velocity, carrying the lighter particles upward and allowing the heavier ones to sink.

b. Purification, or removal of material from a mixture or in suspension in water, by washing and decanting, leaving the heavier particles behind. Syn: water separation.


An appliance for washing or sizing very fine particles, based on the principle that large grains settle at a faster rate through a liquid than small grains of the same material. The medium is commonly an upward current of water. See also: hydraulic classifier; Stokes' law.


a. Said of an incoherent mineral deposit, such as a placer, resulting from the decomposition or disintegration of rock in place. The material may have slumped or washed downslope for a short distance but has not been transported by a stream.

b. Pertaining to eluvium; residual.


a. An accumulation of rock debris produced in place by the decomposition or disintegration of rock; a weathering product; a residue.

b. Fine soil or sand moved and deposited by the wind, as in a sand dune. CF: alluvium.


Cornish term for pneumatolized granite rocks containing tourmaline, fluorite, or topaz.