Appendix:Dictionary of Mining, Mineral, and Related Terms/E/3

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To fix a valuation, but not to appraise.


The fixing of a evaluation, not an appraisal. Used in preference to the word valuation which is often confused with appraisal.


An amorphous mineral, Al (sub 3) (PO (sub 4) )(OH) (sub 6) .6H (sub 2) O(?) ; may contain small amounts of uranium and thorium; associated with limonite and allophane.


To convert into vapor. See also: evaporite.


a. The process, also called vaporization, by which a substance passes from the liquid or solid state to the vapor state. Limited by some to vaporization of a liquid, in contrast to sublimation, the direct vaporization of a solid. Also limited by some (e.g., hydrologists) to vaporization that takes place below the boiling point of the liquid. The opposite of condensation.

b. The process by which a substance is converted from a liquid state into a vapor. Specif., the conversion of a liquid into vapor in order to remove it wholly or partly from a liquid of higher boiling point or from solids dissolved in or mixed with it. CF: distillation; sublimation.

evaporation gage

A graduated vessel of glass for determining the rate of evaporation of a liquid placed in it, in a given time and exposure.

evaporative cooling

a. The conversion of sensible heat to latent heat with addition of moisture and practically no change in total heat content of air.

b. Cooling by the evaporation of water, heat for which is supplied by the air; feasible where the wet-bulb depression is marked, and consequently widely used in dry climates.


A nonclastic sedimentary rock composed primarily of minerals produced from a saline solution as a result of extensive or total evaporation of the solvent. Examples include gypsum, anhydrite, rock salt, primary dolomite, and various nitrates and borates. The term sometimes includes rocks developed by metamorphism or transport of other evaporites. Syn: evaporate; saline deposit; saline residue.

evaporite-solution breccia

A solution breccia formed where soluble evaporites (rock salt, anhydrite, gypsum, etc.) have been removed. See also: solution breccia.


A passage of gradually increasing area through which the air discharged by a fan must pass. The velocity of the air is gradually reduced and much of the kinetic energy is transformed into equivalent pressure energy. See also: volute.

evening emerald

Olivine (peridot or chrysolite varieties) that loses some of its yellow tinge and appears more greenish (like an emerald) in artificial light, used as a gem. Syn: night emerald.


A monoclinic mineral n-tetracosane C (sub 24) H (sub 50) ; forms waxlike crystals in geodes in a vein cutting vesicular tuff, Evenki district, lower Tunguska River, Siberia, Russia.

everlasting lamps

N. of Eng. Natural jets of combustible gases or small blowers that continue to burn as long as gas is given off.

evolutionary operation

A method of process operation that introduces tightly controlled variations designed to transfer laboratory-proved improvements into changes leading to better commercial production.


Letter name specifying the dimensions of bits, core barrels, and drill rods in the E-size and W-group wireline diamond-drilling system having a core diameter of 21.5 mm and a hole diameter of 37.7 mm. CF: EX.


Letter name specifying the dimensions of core, core barrels, and casing in the E-size and X-series wireline diamond-drilling system having a core diameter of 21.5 mm and a hole diameter of 37.7 mm. The EX designation for coring bits has been replaced by the EW designation. Syn: EW.

excavating cableway

Cableway fitted with a bucket suitably designed for excavating.


a. The act or process of removing soil and/or rock materials from one location and transporting them to another. It includes digging, blasting, breaking, loading, and hauling, either at the surface or underground. See also: breaking ground.

b. A pit, cavity, hole, or other uncovered cutting produced by excavation. c. The material dug out in making a channel or cavity.

excavation deformation

The zone around any excavation within which a structure might be disturbed by rock movements resulting from that excavation.


The term embraces a large number of power-operated digging and loading machines. Variants are the grab, skimmer, trencher, rotary digger, bucket wheel, and grader. See also: bulldozer; continuous-bucket excavator; dragline; power shovel; walking dragline.

excavator base machine

A tracted prime mover to which can be fitted a variety of front-end excavating and lifting appliances.

excellent fumes

Fumes that contain a minimum of toxic and irritating chemicals.


A reservation or exception of the minerals in a tract of land conveyed is a separation of the estate in the minerals from the estate in the surface, and it makes no difference whether the word used is excepted or reserved.

excess air

In practice, complete combustion cannot be obtained without slightly more air than is theoretically necessary. The amount of this excess air varies with the design and mechanical condition of the appliance, but ranges from 15% upward.

excessive location

A mining claim in excess of the width allowed by law.

excess spoil

Spoil in excess of that necessary to backfill and grade affected areas to the approximate original contour. The term may include box-cut spoil where it has been demonstrated for the duration of the mining operation, that the box-cut spoil is not needed to restore the approximate original contour.


The addition of energy to a system, thereby transferring it from its ground state to an excited state. Excitation of a nucleus, an atom, or a molecule can result from absorption of photons or from inelastic collisions with other particles or systems.

excitation time

The minimum time for which electric current must flow in the fusehead of a detonator to ensure its ignition.

Exclusive Economic Zone

An area beyond and adjacent to the territorial sea, subject to the specific legal regime established in Part V, Articles 55-75 of the United Nations Convention on the Law of the Sea, under which the rights and jurisdiction of the coastal State and the rights and freedoms of other States are governed by the relevant provisions of the Convention. Abbrev. EEZ. EEZ resources rights include both living and non-living resources of the subsoil and superjacent water of the zone. The EEZ will not extend beyond 200 nmi (364 km) from the baseline from which the territorial sea is measured. CF: continental shelf.

exclusive prospecting license

Grant of right to prospect a designated area for a limited period. Abbrev. EPL.

exempted claim

A mining title on which exemption from otherwise essential activity has been granted.


Exemption laws are grants of personal privileges to debtors, which may be waived by contract or surrender or by neglect to claim before sale.


To peel off in concentric layers, as some rocks weather.


a. The process by which concentric scales, plates, or shells of rock, from less than a centimeter to several meters in thickness, are successively spalled or stripped from the bare surface of a large rock mass. It is caused by physical or chemical forces producing differential stresses within the rock, as by expansion of minerals as a result of near-surface chemical weathering, or by the release of confining pressure of a once deeply buried rock as it is brought nearer to the surface by erosion. It often results in a rounded rock mass or dome-shaped hill. CF: spheroidal weathering; spheroidal parting. Syn: spalling; scaling; sheeting; sheet jointing.

b. The property of some silicate minerals, e.g., vermiculite, or rocks, e.g., perlite, to expand permanently when heated to form an irregular or vesicular structure. CF: intumescence.

exfoliation dome

A large dome-shaped form, developed in massive homogeneous coarse-grained rocks, esp. granite, by exfoliation; well-known examples occur in Yosemite Valley, CA.


a. The streaming-forth of volcanic gases; also, the escape of gases from a magmatic fluid.

b. Any vapor or gas arising from substances or surfaces exposed to the atmosphere. c. Any gas or vapor formed beneath the surface of the Earth and escaping either through a conduit or fissure, or from molten lava or a hot spring; an emanation. d. An exhaling or sending forth, as of steam or vapor. Something that is exhaled or given off or that rises in the form of a gas, fumes, or steam, for example, a foul exhalation from the marsh.

exhaust fan

In coal mining, a fan that sucks used air from a mine and thereby causes fresh air to enter by separate entries to repeat the cycle.

exhausting auxiliary fan

An auxiliary fan that exhausts air from the face of a tunnel through ducting or piping and discharges it into the return side of the airway off which the tunnel branches. See also: extraction ventilation; auxiliary ventilation; suction fan.


In mining, the complete removal of ore reserves.

exhaust ventilation

A system of ventilation in which the fan draws air through the workings by suction. Opposite of forced ventilation. See also: auxiliary ventilation.


a. M.C. Stopes in 1935 used the term exinite for the constituent represented by the exines of spores in coal. C.A. Seyler in 1932, however, used the term with its present meaning designating the following group of macerals--sporinite, cutinite, alginite, resinite. The macerals grouped under the term exinite are not necessarily exines but appear to have similar technical properties. The term liptinite was introduced by A. Ammosov in 1956. Little information is so far available on the technological behavior of pure exinite. By comparison and extrapolation it has proved possible, however, to deduce that in coals with more than 35% volatile matter exinite is the maceral group richest in volatile matter and in hydrogen (about 80% and about 9%, respectively). In coals with 18% to 25% volatile matter, exinite is more resilient than the vitrinite; in coals with more than 25% volatile matter, it has even greater resilience than micrinite. Exinite, therefore, increases the strength of bands in which it occurs and in broken coal concentrates in particles greater than 1 mm.

b. The micropetrologic constituent, or maceral, of spore exines and cuticular matter. See also: sporinite; cutinite. c. A coal maceral group including sporinite, cutinite, alginite, resinite, and liptodetrinite, derived from spores, cuticular matter, resins, and waxes. Exinite is relatively rich in hydrogen. It is a common component of attrital coal. CF: inertinite; vitrinite. Syn: liptinite.


A coal constituent similar to material derived from plant exines.


A claim corner whose position is evidenced by a monument or its accessories as described in the field note record, or whose location can be identified by the aid of acceptable testimony. �! �j- �l- :D6�� � % DICTIONARY TERMS:exogene See: exogenetic. See: exogenetic.


a. Said of processes originating at or near the surface of the Earth, such as weathering and denudation, and of rocks, ore deposits, and landforms that owe their origin to such processes. CF: endogenetic. Syn: exogene; exogenic; exogenous.

b. Said of energy sources and objects of extraterrestrial origin, as solar radiation, cosmic rays, meteorites, and cosmic dust.


See: exogenetic.


See: exogenetic.

exogenous inclusion

See: xenolith.


A descriptive term for those changes produced by contact metamorphism in the wall rock of the intrusion; opposite of endomorphic.


See: exomorphism.

exomorphic metamorphism

See: exomorphism.


Changes in country rock produced by the intense heat and other properties of magma or lava in contact with them; it is a form of contact metamorphism in the usual sense. The term was originated by Fournet in 1867. CF: endomorphism. Syn: exometamorphism; exomorphic metamorphism.


Applied to a boulder, block, or larger rock body unrelated to the rocks with which it is now associated, which has been moved from its place of origin by one of several processes. Exotic masses of tectonic origin are also allochthonous; those of glacial or ice-rafted origin are generally called erratics.

exotic limonite

Limonite precipitated in rock that did not formerly contain any iron-bearing sulfide. CF: indigenous limonite.

expanded blast-furnace slag

The lightweight cellular material obtained by controlled processing of molten blast-furnace slag with water or with water and other agents, such as steam or compressed air or both.

expanding electrode test

A geophysical test based on the resistivity method to determine underground geological structure.

expanding reamer

A reamer capable of slight adjustment in diameter by means of a coned internal plug acting in a partially split length of the tool.

expanding waterway

A channel or groove incised into and across the face of a bit, the depth and/or width of which gradually increases from the inside to the outside walls of the bit.

expansion bit

A drill bit that may be adjusted to cut various sizes of holes. The adjustment of some types may be accomplished by mechanical means while the bit is inside the borehole. Also called paddy; paddy bit.

expansion bolt

A bolt equipped with a split casing that acts as a wedge; used for attaching to brick or concrete.

expansion cutter

A borehole drill bit having cutters that may be expanded to cut a larger size hole than the size of the bit in its unexpanded state; also, a device equipped with cutters that may be expanded inside casing or pipe to sever, or cut slits or holes in, the casing or pipe. CF: paddy.

expansion dome

Imaginary dome of rock above underground working, matched by a similar inverted dome below the stope. The dome lies inside the zone of stress due to an unsupported ground, but it is partially destressed owing to expansion and peripheral transfer of load.

expansion fissure

In petrology, one of a system of fissures that radiate irregularly through feldspar and other minerals adjacent to olivine crystals that have been replaced by serpentine. The alteration of olivine to serpentine involves considerable increase in volume, and the stresses so produced are relieved by the fissuring of the surrounding minerals. This phenomenon is common in norite and gabbro.

expansion loop

Either a bend like the letter U or a coil in a line of pipe to provide for expansion or contraction.

expansion ring

A hoop or ring of U-section used to join lengths of pipe so as to permit of expansion.

expected tonnage

The calculated tonnage of recoverable ore in the mine.

experimental face

A normal longwall face on which new machines, such as a cutter loader, may be put to work to gain experience and perhaps improved. Such trials may disclose weaknesses, and they would also indicate the best support system, turnover, and other operating factors. See also: standby face. Syn: trial face.

experimental mineralogy

The study of chemical and isotopic variations in minerals as a function of temperature and pressure. CF: chemical mineralogy; crystallogeny; phase equilibria.


a. A cap or fulminating cartridge, placed in a charge of gunpowder or other explosive, and exploded by electricity or by a fuse. Also called detonator. Syn: battery.

b. Electric shot-firing apparatus specially designed to provide a source of electric energy of sufficient power to fire electric detonators. Each type of exploder is designed to fire a specific number of shots in series, and exploders are rated accordingly; e.g., single-shot exploders, 30-shot exploders, and 100-shot exploders. See also: Beethoven exploder. Syn: blasting unit. c. A chemical employed for the instantaneous explosion of powder.

exploding bridge wire

A wire that explodes upon application of current. It takes the place of the primary explosive in an electric detonator.


a. Excavate in such a manner as to utilize material in a particular vein or layer, and waste or avoid surrounding material.

b. Turn a natural resource to economic account. For example, to exploit a mineral deposit.


a. The process of winning or producing from the Earth the oil, gas, minerals, or rocks that have been found as the result of exploration.

b. The extraction and utilization of ore.


a. The search for coal, mineral, or ore by (1) geological surveys; (2) geophysical prospecting (may be ground, aerial, or both); (3) boreholes and trial pits; or (4) surface or underground headings, drifts, or tunnels. Exploration aims at locating the presence of economic deposits and establishing their nature, shape, and grade, and the investigation may be divided into (1) preliminary and (2) final. See also: preliminary exploration. Also called prospecting.

b. A mode of acquiring rights to mining claims.

exploration drilling

Drilling boreholes by the rotary, diamond, percussive, or any other method of drilling for geologic information or in search of a mineral deposit.

exploratory drift

A drift that is driven in an ore deposit for the purpose of exploring the deposit both horizontally and vertically to see whether it will be worth working.

exploratory drilling

The drilling of boreholes from the surface or from underground workings, to seek and locate coal or mineral deposits and to establish geological structure. Exploratory drilling is frequently done from underground workings, the holes being drilled upward, horizontally, or downward as required. For underground drilling, roller bits, diamond crowns, or tungsten-carbide bits may be used and can be coring or noncoring. Rotary boring is the predominant method for exploratory work from the surface, particularly where cores of significant deposits are required. See also: borehole samples; drill sampling; underground exploration; diamond drilling.

exploratory work

Mining operations to determine the size of a deposit, and also its character along the strike as well as its dip. This is done by making drives and inclines. These openings follow the deposit both in strike and dip. They are designed in such a way so as to make it possible to use them for mining proper should the exploration turn out favorably. Syn: exploration.

explorer's alidade

See: gale alidade.

exploring drift

The working drift approaching old workings whose exact position is uncertain, bored as a precaution against an unexpected holing.

explosibility curves

Curve lines drawn through coordinating points, indicating ignition or propagation, in which the rectilinear coordinates of the diagram are factors of volatile fixed-carbon ratios, total incombustible, density of dust, size of dust particles, and combustible gases, if any, in the air current.

explosibility limit

The addition of inert dust to coal dust decreases its explosibility, and when enough has been added an explosion cannot occur. The point at which explosion cannot occur is said to be the explosibility limit of the coal in question.


Capable of being exploded.

explosion dust

The dust deposited from the cloud raised by the explosion, which settles after the explosion has died down, only part of which may be traversed by the flame.

explosion-hazard investigation

The investigation of a mine to determine the possibility of an explosion occurring by reason of the kind, size, purity, and dryness of the coal dust along the mine passages and the presence or absence of combustible gases. It also determines the degree of the hazard of an explosion from natural conditions and of one arising through the neglect or ignorance of the mine personnel. The purpose of such investigations is to make specific recommendations for reducing that hazard to a negligible point by appropriate methods and continued diligence.

explosion pressure

The pressure developed at the instant of an explosion.

explosion proof

a. The term "explosion-proof casing" or "enclosure" means that it is so constructed and maintained as to prevent the ignition of gas surrounding it by any sparks, flashes, or explosions of gas that may occur within such enclosures.

b. Said of electrical apparatus so designed that an explosion of flammable gas inside the enclosure will not ignite flammable gas outside. Also called flameproof. c. Fitting, motor, switch, or fixture so made and maintained as to preclude possibility of sparks, arcs, or heat sufficient to initiate explosion in surrounding air or mine dust.

explosion-proof motor

The U.S. Bureau of Mines has applied the term "explosion proof" to motors constructed so as to prevent the ignition of gas surrounding the motor by any sparks, flashes, or explosions of gas or of gas and coal dust that may occur within the motor casing. See also: permissible motor.

explosions from molten iron

An explosion caused by molten iron coming in contact with water or wet material.

explosion-tested equipment

In explosion-tested equipment, housings for electric parts are designed to withstand internal explosions of methane-air mixtures without causing ignition of such mixtures that surround the housings.

explosion tuff

A tuff whose pyroclastic fragments are in the place in which they fell, rather than having been washed into place after they landed.

explosion wave

The wave or flame that passes through a uniform gaseous mixture with a permanent maximum velocity. The rate of the explosion wave is a definite physical constant for each mixture. The explosion wave travels with the velocity of sound in the burning gas, which itself is moving rapidly forward en masse in the same direction, so that the explosion wave is propagated far more rapidly than sound travels in the unburned gas.


a. Any chemical compound, mixture, or device that is capable of undergoing a rapid chemical reaction, producing an explosion; a cap sensitive mixture.

b. Any mixture or chemical compound by whose decomposition or combustion gas is generated with such rapidity that it can be used for blasting or in firearms; e.g., gunpowder, dynamite, etc. See also: explosive factor; Morcol; permitted explosive; sheathed explosive. c. In coal mining, there are two main classes permissible and nonpermissible; i.e., those safe for use in coal mines and those that are not. See also: coal mining explosives.

explosive antimony

A black powder obtained either by the rapid cooling of antimony vapor or by the electrolysis of a solution of antimony chloride in hydrochloric acid, using a platinum cathode and an antimony anode. When scratched, the hard black mass deposited on the cathode will explode. The mass may consist of a solid solution of antimony trichloride in metallic antimony.

explosive cooling agent

A substance added to a permitted explosive to cool the explosion flame and thus reduce the risk of igniting mine gases. The agent may be sodium chloride and sodium bicarbonate.

explosive drilling

A technique developed for deep-hole drilling in esp. strong and abrasive rocks. In this method, a series of small underwater explosions are used to break the rock at the bottom of the hole, the fragments from each explosion being washed away by the flushing water.

explosive dusts

Dusts that are combustible when airborne. They include metallic dusts (magnesium, aluminum, zinc, tin, iron), coal (bituminous, lignite), and sulfide ores.

explosive factor

The ratio between the burden of a shothole in tons or cubic yards and the weight of explosive charge in pounds; i.e., tons (cubic yards) per pound of explosive. The factor is dependent on the rock and the fragmentation required, but 5 st/lb (10 t/kg) is about average in quarry blasting. See also: loading ratio.

explosive force

A force represented with separate values for the heat liberated by the explosive decomposition and the detonating rate.

explosive limits

The limits of percentage composition of mixtures of gases and air (or oxygen) within which an explosion takes place when the mixture is ignited.

explosive loading factor

See: powder factor.

explosively anchored rockbolt

A device to give better support in underground mining operations. It can be anchored more firmly than conventional bolts because the principle of explosive forming enables the anchor to grip the sides of the borehole along its entire length, if necessary. The key to the design is a seamless steel anchoring tube, welded to the threaded end of the bolt. Exploding a small charge inside the tube makes it expand to fit tightly in the borehole. Water, wax, or a similar buffer surrounds the charge to distribute the force of the explosion evenly and prevent it from rupturing the tube. Its use may permit mining of mineral deposits formerly considered uneconomic because of the hazards encountered in loose rock formations.

explosiveness of dust

The ability of a dust to produce violent effects; it is measured by the pressure produced after the explosion has traveled a fixed distance under standard conditions.

explosive oil

See: nitroglycerin.

explosive ratio

The weight of explosive per cubic feet (cubic meter) of rock broken. Also called powder factor. See also: loading ratio.

explosives casting

In explosives casting, large amounts of low-cost ammonium nitrate mixtures are loaded into medium-sized drill holes in a usual ratio of more than 1 lb of powder per cubic yard (0.59 kg/m (super 3) ) of overburden. The explosive charges are detonated through millisecond-delay electric blasting caps. When the shot is fired, a large part of the overburden is blasted into the pit away from the high wall and up on the spoil pile where it attains a favorable angle of repose.

explosive sensitiveness

The ease with which an explosive will detonate or explode.

explosive shattering

This method consists in soaking the ore thoroughly in water and then heating to 180 degrees C under a pressure of 150 psi (1.03 MPa). The pressure is then suddenly released, and the absorbed water is converted to steam, which shatters and liberates mineral particles without harmful overgrinding of the ore.

explosive store

A surface building at a mine where explosives and detonators may be kept.

explosive strength

A measure of the amount of energy released by an explosive on detonation and its capacity to do useful work. Several methods of expressing explosive strength are used, but in most cases the figures are calculated from the deflection of a freely suspended ballistic mortar in which small explosive charges are fired.

explosive stripping

A method in which, by using an excess of explosives in the strip mine bench, up to about 40% of the overburden can be removed from the coal seam by the energy of the explosive, thereby requiring no excavation.

exponential model

A function frequently used when fitting mathematical models to experimental variograms, often in combination with a nugget model.

exposed coalfield

a. A coalfield where the coal measures crop out at the surface all around its margin or boundary. South Wales, England, is a good example of an exposed coalfield. See also: coal basin; concealed coalfield.

b. Deposits of coal that crop out at the surface, as along the rim of a coal basin. CF: crop coal.


a. An area of a rock formation or geologic structure that is visible (hammerable), either naturally or artificially, i.e., is unobscured by soil, vegetation, water, or the works of humans; also, the condition of being exposed to view at the Earth's surface. CF: outcrop.

b. The nature and degree of openness of a slope or place to wind, sunlight, weather, oceanic influences, etc. The term is sometimes regarded as a syn. of aspect. c. The proportional mass of a diamond or other cutting medium protruding beyond the surface of the metal in which it is inset in the face of the bit. Sometimes incorrectly called clearance. d. The total quantity of light received per unit area on a sensitized plate or film, usually expressed as the product of the light intensity and the time during which the light-sensitive material is subjected to the action of light. A loosely used term generally understood to mean the length of time during which light is allowed to act on a sensitive surface. The act of exposing a light-sensitive material to a light source. An individual picture of a strip of photographs.

exsiccated alum

See: burnt alum.


The process whereby an initially homogeneous solid solution separates into two (or possibly more) distinct crystalline phases without addition or removal of material, i.e., without change in the bulk composition. It generally, though not necessarily, occurs on cooling. Syn: unmixing.


Applied to those sedimentary rocks that solidify from solution either by precipitation or by secretion.

exsolution texture

A general term for the texture of any mineral aggregate or intergrowth formed by exsolution. It is generally fairly homogeneous, ranging from perthitic to geometrically regular. See also: eutectic texture.

extendable conveyor

a. For bulk materials it is usually of troughed design and may be lengthened or shortened while in operation. Commonly used in underground mine conveyor work.

b. For packaged materials, objects, or units, the conveyor may be one of several types including roller, wheel, and belt conveyors. Construction is such that the conveyor may be lengthened or shortened within limits to suit operating needs. See also: telescoping conveyor.

extended charges

Explosive charges spaced at intervals in a quarry or opencast blast hole. See also: deck loading.

extensible conveyor

A conveyor capable of being lengthened or shortened while in operation.

extensible discharge trough

Consists of two or more shaker conveyor troughs, nested, to be installed on the discharge end of the pan line so as to provide for adjustment of the position of the discharge point. After adjustment, they are locked in place.


Part of and physically associated with a known mineral deposit, but outside of the identified parts.

extensional fault

See: tension fault.

extension fracture

A fracture that develops perpendicular to the direction of greatest stress and parallel to the direction of compression; a tension fracture. See also: extension joint.

extension joint

A joint that forms parallel to the direction of compression; a joint that is an extension fracture. See also: extension fracture.

extension ore

Ore believed to exist ahead of ore exposed in the face of a drift. See also: probable ore.


a. Instrument used for measuring small deformations, deflections, or displacements.

b. An instrument for measuring changes caused by stress in a linear dimension of a body.

external sintered tip pick

See: sintered carbide-tipped pick.


In polarized-light microscopy with crossed polars and an anisotropic mineral in the light train, when the two electric vectors (permitted light or vibration directions) of a randomly oriented crystal are each parallel to those of the polars, no light is transmitted and the crystal is at extinction. Isotropic crystals and anisotropic crystals viewed parallel to an optic axis remain extinct upon stage rotation, while randomly oriented anisotropic crystals go extinct four times upon stage rotation of 360 degrees . CF: anisotropy; extinction angle; extinction direction; inclined extinction; optic axis; parallel extinction; undulatory extinction.

extinction angle

The angle between a crystallographic direction and a position of maximum extinction of an anisotropic crystal as viewed with a polarized-light microscope or polariscope. It can be diagnostic in mineral identification. Syn: angle of extinction. CF: inclined extinction; extinction.

extinction direction

In polarized-light microscopy, the angular position of extinction with respect to a crystallographic axis, a crystal face, a cleavage plane, or a twin plane. CF: extinction.

extinctive atmosphere

An atmosphere created behind mine seals when the supply of oxygen is completely cut off, thereby bringing combustion to an end.

extractable metal

Metal that can be extracted from a sample by a specified chemical treatment, ordinarily only part of the metal that is in the sample. Often abbreviated as "Ex Zn, Ex Cu," etc., indicating the metal of interest. The process is referred to as partial extraction, or selective extraction. Syn: readily extractable metal.


In solvent extraction, the active organic reagent that forms an extractable complexion with the metal.


a. The process of mining and removal of coal or ore from a mine.

b. Used in relation to all processes of obtaining metals from ores. Broadly, these processes involve breaking down ore both mechanically (crushing) and chemically (decomposition), and separating the metal from the associated gangue. Extractive metallurgy may be conveniently divided into beneficiation, pyrometallurgy, hydrometallurgy, and electrometallurgy. c. A designation for that part of the metallic content of the ore obtained by a final metallurgical process, e.g., the extraction was 85%. CF: recovery. d. The process of dissolving and separating out specific constituents of a sample by treatment with solvents specific for those constituents. e. In chemical engineering, the operation wherein a liquid or solid mixture is brought into contact with an immiscible or partially miscible liquid to achieve a redistribution of solute between the phases.

extraction metallurgy

Process of producing metal from ores or their concentrates.

extraction ratio

Ratio of the mined volumes to the total volumes. Also called strip ratio.

extraction ventilation

The ventilation of a tunnel face (or mine) by an exhaust fan. See also: exhausting auxiliary fan. Syn: exhaust ventilation.

extraction water

Superheated water pumped into wells to melt and to extract molten sulfur from salt domes.

extractive metallurgy

The extraction of metals from their ores or from the naturally occurring aggregates of minerals by various mechanical and chemical methods. The major divisions of extractive metallurgy may be classified as mineral dressing, pyrometallurgy, hydrometallurgy, and electrometallurgy.


The exterior arc of an arch, as in a tunnel.


The fractured ground outside of the fracture zone. In many mines, extradosal bursts occur more frequently than intradosal; i.e., the extradosal ground ahead of the working face serves as an abutment that supports the superincumbent rock to the surface. CF: intradosal.

extra dynamite

Differs from straight dynamite in that a portion of the nitroglycerin content is replaced with sufficient ammonium nitrate to maintain the grade strength, manufactured in grade strengths of from 20% to 60%. It is lower in velocity and water resistance than straight dynamite, but is less sensitive to shock and friction and less flammable. See also: ammonia dynamite; low-density explosive.

extraflexible hoisting rope

A rope consisting of 8 strands of 19 wires each with a large hemp center.


Unusually dangerous; specif. used in insurance in classifying occupational risks, as mining is extrahazardous.


Situated or extending beyond the sides; specif. noting the right of a mine owner to the extension of a lode or vein from his or her claim beyond the sidelines, but within the vertical planes through the endlines.

extralateral rights

Among numerous provisions, the statute (30 USC 26) provides that extralateral rights to veins, lodes, and ledges that come to an apex within the boundary lines and dip downward so as to extend outside the vertical planes through the side lines belong to the owner of such lode location. The extralateral portion of the vein is that part that extends on its downward dip through the vertical planes along the side lines.


An explosive mixture consisting of ammonium nitrate and carbonate, liquid and solid hydrocarbons, and zinc chlorate.

extraneous ash

Ash in coal that is derived from inorganic material introduced during formation of the seam, such as sedimentary particles, or filling cracks in the coal. See also: ash; ash yield; inherent ash. Syn: secondary ash; sedimentary ash.

extraneous electricity

Electrical energy, other than actual firing current or the test current from a blasting galvanometer, that is present at a blast site and that could enter an electric blasting circuit; such electricity can include lightning, current from high tension powerline, and static charge carried on a person.

extraordinary ray

Light passing through anisotropic crystals is doubly refracted with one or both ray directions not parallel to their wave normals. Such light rays do not follow Snell's law [n=(sin i)/(sin r)] of ordinary refraction and are termed "extraordinary." Also written E-ray or e-ray. CF: law of refraction.


Projection of a graphic curve beyond the line of points established from plotting data.

extra-special improved plow

A grade of wire rope used for winding, with a tensile strength of between 115 st/in (super 2) and 125 st/in (super 2) (16.2 t/cm (super 2) and 17.6 t/cm (super 2) ).

extraterrestrial mining

The mining of metals and minerals on locations other than the Earth through space colonization of planets and moons.

extraterritorial rights

Sometimes affect employment in alien countries by giving immunity from some laws. May affect working conditions.


a. The emission of relatively viscous lava onto the Earth's surface; also, the rock so formed. CF: effusion.

b. The operation of producing rods, tubes, and various solid and hollow sections, by forcing heated metal through a suitable die by means of a ram; applied to numerous nonferrous metals, alloys, and other substances. c. The act or process of extruding; thrusting or pushing out; also, a form produced by the process; a protrusion. d. The emission of magmatic material (generally lavas) at the Earth's surface; also, the structure or form produced by the process, such as a lava flow, a volcanic dome, or certain pyroclastic rocks. e. Lava or mud forced out, as through a vent or fissure, onto the Earth's surface. f. Plastic clay forced through a mouthpiece of a pugmill or a press, forming a rod or a tube, which can be cut to the desired length.


Said of igneous rock that has been erupted onto the surface of the Earth. Extrusive rocks include lava flows and pyroclastic material such as volcanic ash. An extrusive rock. CF: intrusive. Syn: effusive; volcanic; eruptive.


The action by which all or a portion of the low-melting constituent of a compact is forced to the surface during sintering. Sometimes referred to as "bleed out." Syn: sweating.

ex vessel

A price quoted ex vessel used in connection with a port name means all costs paid until free of the ship's tackle at the port designated.


a. The top or mouth of a shaft.

b. The central or intake opening of a radial-flow fan. c. The entrance to a mine working at which daylight can be seen from within. d. The hole in a pick or hammer head, that receives the handle. e. The opening at the top of a beehive coke oven for charging. f. The opening in the bottom of a pot furnace through which the flame enters.

eye agate

Agate displaying concentric bands, commonly of various colors, about a dark center suggesting an eye. Also called Aleppo stone.


A rod or bolt having an eye or loop at one end and threaded at the other end.


A window or other opening in a tuyere through which the operator can see into the melting zone of the blast furnace.


A triclinic mineral, Na (sub 4) B (sub 10) O (sub 17) .7H (sub 2) O ; (super ) (sub ) associated with kernite, borax, and tincalconite at the Tincalayu borax mine, Salta province, Argentina.