Appendix:Dictionary of Mining, Mineral, and Related Terms/A/2

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A monoclinic mineral, NiSeO (sub 3) .2H (sub 2) O; forms a series with cobaltomenite; rose colored; vitreous luster; no cleavage; conchoidal fracture; strongly pleochroic, X rose, Y pale green, Z brown green; from Pacajake, Bolivia.


In a soil profile, the uppermost zone from which soluble salts and colloids have been leached and in which organic matter has accumulated. See also: B-horizon.


a. An orthorhombic mineral, PbCuBiS (sub 3) ; sp gr, 6.1 to 6.8; an ore of lead, copper, and bismuth. Syn: acicular bismuth; aciculite; needle ore; acicular bismuth; aciculite.

b. Wolframite pseudomorphous after scheelite.


See: hemafibrite.


American Institute of Mining and Metallurgical Engineers.


a. The mixture of gases that surrounds the Earth and forms its atmosphere; composed by volume of 21% oxygen and 78% nitrogen; by weight about 23% oxygen and 77% nitrogen. It also contains about 0.03% carbon dioxide, some aqueous vapor, argon, and other gases.

b. The current of atmospheric air circulating through and ventilating the workings of a mine. c. Atmospheric air delivered under compression to bottom of drill hole through the drill stem and used in place of water to clear the drill bit of cuttings and to blow them out of the borehole. d. Air piped under compression to work areas and used to operate drilling or mining machinery. See also: air circulation.


See: hemafibrite.

air-avid surface

A surface that seems to prefer contact with air to contact with water. A particle (or mineral) of this sort will adhere to an air bubble and float out of a flotation pulp; otherwise, the particle will not float. Also called water-repellent surface; hydrophobic. CF: water-avid surface.

air barrage

The division of an opening in a mine by an airtight wall into two sides; one side is used as an air intake, the other side as a return.

air bell

In froth flotation, the small air pocket inducted or forced into the pulp at depth; e.g., bell and the two-walled semistable bubble after emergence from pulp into froth have different characteristics and gas-to-liquid, area-to-volume relationships, hence the distinction. These bubbles vary in attractive and retaining power for aerophilic grains and are a critical component of the flotation process. Syn: air bubble.

air belt

In a cupola furnace, an annular air space around the furnace, from which air is forced into the furnace.


a. A term improperly used by some diamond drillers as a syn. for air circulation. See also: air circulation.

b. A disturbance in underground workings accompanied by a strong rush of air. The rush of air, at times explosive in force, is caused by the ejection of air from large underground openings, the sudden fall of large masses of rock, the collapse of pillars, slippage along a fault, or a strong current of air pushed outward from the source of an explosion.


A method of blasting in which compressed air at very high pressure is piped to a steel shell in a shot hole and discharged.

air block

Air trapped in the upper end of an unvented inner tube of a double-tube core barrel, which, when sufficiently compressed, acts like a solid and stops further advance of core into the inner tube. Syn: air cushion.

airborne electromagnetic prospecting

Electromagnetic surveys carried out with airborne instruments.

airborne magnetic prospecting

See: aeromagnetic prospecting.

airborne magnetometer

An instrument used to measure variations in the Earth's magnetic field while being transported by an aircraft. See also: magnetometer.

air box

a. A rectangular wooden pipe or tube made in lengths of 9 to 15 ft (2.7 to 4.6 m) for ventilating a heading or a sinking shaft.

b. A box for holding air. c. The conduit through which air for heating rooms is supplied to a furnace.

air breakers

A method of breaking down coal by the use of high-pressure compressed air.

air brick

A hollow or pierced brick built into a wall to allow the passage of air.

air bridge

A passage through which a ventilating current is conducted over an entry or air course; an overcast. See also: air crossing.

air bubble

See: air bell.

air chamber

A vessel installed on piston pumps to minimize the pulsating discharge of the liquid pumped. The chamber contains air under pressure and is fitted with an opening on its underside into which some of the liquid from the pump is forced upon the delivery stroke of the piston. The air acts as a cushion to lessen the fluctuation of the liquid flow between the suction and delivery strokes of the piston.

air change

a. The quantity of infiltration of ventilation air in cubic meters per second divided by the volume of the room gives the number of so-called air changes during a given interval of time. Tables of the recommended number of such air changes for various rooms are used for estimating purposes.

b. The act of instituting a different pattern of air flow in a mine.

air channels

In a reverberatory furnace, flues under the hearth and fire bridge through which air is forced to avoid overheating.

air circulation

a. A large volume of air, under compression, used in lieu of a liquid as a medium to cool the bit and eject drill cuttings from a borehole. Syn: air flush. See also: airblast.

b. The general process of moving air around the openings of a mine. See also: air.

air classification

a. In powder metallurgy, the separation of powder into particle-size fractions by means of an airstream of controlled velocity; an application of the principle of elutriation.

b. Sorting of finely ground minerals into equal settling fractions by means of air currents. These are usually controlled through cyclones, which deliver a coarse spigot product and a relatively fine vortical overflow. See also: infrasizer. c. A method of separating or sizing granular or powdered materials, such as clay, through deposition in air currents of various speeds. This principle is widely used in continuous pulverizing of dry materials, such as frit, feldspar, limestone, and clay. See also: air classifier; air elutriator.

air classifier

An appliance for approx. sizing crushed minerals or ores by means of currents of air. See also: air classification; air elutriator.

air cleaning

A coal-cleaning method that utilizes air to remove the dust and waste from coal. Air cleaning requires that the coal contain less than 5% of surface moisture as a rule. It is effective only in the coarse sizes (plus 10 to 28 mesh) and is best suited to coals having a sharply defined line between coal and refuse material. Predrying to reduce the moisture content of the coal ahead of the air treatment is not uncommon. It is a less expensive and also a less accurate method of cleaning coal than the wet-cleaning method.

air compartment

An airtight portion of any shaft, winze, raise, or level used for ventilation.

air conditioning

The simultaneous control, within prescribed limits, of the quality, quantity, temperature, and humidity of the air in a designated space. It is essentially atmospheric environmental control. Control of only one or two of these properties of the atmosphere does not constitute air conditioning. The definition and correct usage require that the purity, motion, and heat content of the air must all be maintained within the prescribed limits.

air-conditioning process

When conditioning is designed to perform only one or a limited number of functions, then it should be so designated. Air-conditioning processes include dust control, ventilation, dehumidification, cooling, heating, and many others. See also: aftercooler; air receiver; compressed air; duplex compressor; rotary compressor; turbocompressor.

air-cooled blast-furnace slag

The material resulting from solidification of molten blast-furnace slag under atmospheric conditions. Subsequent cooling may be accelerated by application of water to the solidified surface.

air course

a. Ventilating passage underground.

b. A passage through which air is circulated, particularly a long passageway driven parallel to the workings to carry the air current. See also: airway.

air coursing

The system of colliery ventilation, introduced about 1760, by which the intake air current was made to traverse all the underground roadways and faces before passing into the upcast shaft.

air creep

Stain formed by air entering at edges of mica sheets and penetrating along cleavage planes.

air crossing

A bridge where a return airway passes over (overcast) or under (undercast) an intake airway. It is generally constructed with concrete blocks, structural steel, and/or sheet metal, and is made airtight to prevent intermixing of the two air currents. The mining law requires an air crossing to be so constructed as not to be liable to be damaged in the event of an explosion. Syn: air bridge; bridge; overcrossing; overgate. See also: overcast; undercast.

air current

a. The flow of air ventilating the workings of a mine. Syn: airflow; air quantity.

b. A body of air moving continuously in one direction.

air cushion

Air trapped in the bottom of a dry borehole by the rapid descent of a tight string of borehole equipment. Syn: air block.

air cyclone

Primarily a vessel for extracting dust from the atmosphere.

air decking

The use of air space or a void within a blast hole between an explosive charge and inert stemming to enhance the shock wave detonation force.

air dome

A cylindrical or bell-shaped container closed at the upper end and attached in an upright position above and to the discharge of a piston-type pump. Air trapped inside the closed cylinder acts as a compressible medium, whose expansion and contraction tends to reduce the severity of the pulsations imparted to the liquid discharged by each stroke of a pump piston. Syn: bonnet; pressure dome. CF: dome.

air door

A door erected in a roadway to prevent the passage of air. When doors are erected between an intake and a return airway, they may be known as separation doors. Syn: door; separation door; trapdoor.


A system for breaking down coal by which compressed air, generated locally by a portable compressor at 10,000 psi (69.0 MPa), is used in a releasing cylinder, which is placed in a hole drilled in the coal. Thus, slow breaking results, with no flame, in producing a larger percentage of lump coal than is made by using explosives. Its principal advantage is that it may be used with safety in gaseous and dusty mines. See also: compressed-air blasting.

air drain

A passage for the escape of gases from a mold while the molten metal is being poured.


Said of minerals naturally dried to equilibrium with the prevailing atmosphere.

air-dried basis

An analysis expressed on the basis of a coal sample with moisture content in approximate equilibrium with the surrounding atmosphere.

air drift

a. An opening driven for ventilation purposes, often inclined and driven in stone.

b. A drift connecting a ventilation shaft with the fan.

air drill

a. A small diamond drill driven by either a rotary or a reciprocating-piston air-powered motor; used principally in underground workings.

b. As used by miners, a percussive or rotary-type rock drill driven by compressed air. CF: air rig.


a. Dry to such a degree that no further moisture is given up on exposure to air. Most air-dry substances contain moisture that can be expelled by heating them or placing them in a vacuum.

b. Said of timber the moisture content of which is in approximate equilibrium with local atmospheric conditions.

air duct

a. Tubing that conducts air, usually from an auxiliary fan, to or from a point as required in the mine.

b. An air box, canvas pipe, or other air carrier for ventilation.

air elutriation

Method of dividing a substance into various particle sizes by means of air currents.

air elutriator

An appliance for producing, by means of currents of air, a series of sized products from a finely crushed mineral (e.g., for the paint or abrasive industries). See also: air classification; air classifier.

air endway

A narrow roadway driven in a coal seam parallel and close to a winning headway chiefly for ventilation; it usually acts as a return and is connected at intervals of 10 yd (9 m) or so to the headway by crosscuts.

air-float table

Shaking table in which ore is worked dry, air being blown upward through a porous deck so as to dilate the material.


See: air current.

airflow-equalizing device

A flow-equalizing device that is fitted to tube breathing apparatus. There are two kinds in general use, one consisting of a flexible, corrugated rubber tube and the other a canvas fabric bag. On inspiration, air is drawn partly from the equalizer, which is reduced in volume, and partly from the tube. On expiration, the equalizer restores itself to its original volume and in doing so draws air through the tube. Thus the air is kept flowing very nearly in a continuous stream, and the wearer, without the aid of bellows or rotary blower, experiences very little resistance to breathing.

airflow meter

An instrument that measures and provides readout of the flow of air in a pipe or hose in cubic meters per second.

air flush

See: air circulation.

air flushing

The circulation of air through the drilling apparatus during drilling to cool the bit and to remove the cuttings from the hole.

airfoil fan

A fan with an airfoil-shaped blade that moves the air in the general direction of the axis about which it rotates.

air gate

Malleable-iron furnace. �� ��� ��� � � k DICTIONARY TERMS:air gate a. Mid. An underground roadway used princi

a. Mid. An underground roadway used principally for ventilation. b. An air regulator.


A tool in which a hammerhead is activated by means of compressed air. The airhammer is called a jackhammer in coal mining and jackleg-hammer in hardrock mining. The tool is used to drill blastholes to grade or take up bottom or to advance a stope.

air heater

An appliance to warm the air as it enters the downcast shaft or intake drift. In countries where the winter is very cold, nearly all mines are equipped with air heaters of the oil-fired, gas-fired, or electric type.

air hoist

a. Hoisting machinery operated by compressed air.

b. A small portable hoisting machine usually mounted on a column and powered by a compressed air motor. Also called tugger.


a. A small excavation or hole made to improve ventilation by communication with other workings or with the surface. See also: cundy.

b. A venthole in the upper end of the inner tube of a double-tube core barrel to allow air and/or water entrapped by the advancing core to escape. c. A void, cavity, or flaw in a casting or bit crown.

air horsepower

The rate at which energy is consumed, in horsepower or kilowatt units, in moving air between two points.

air hp

Abbrev. for air horsepower.


Operation in which air is blown through molten copper in a wire bar or anode furnace. Sulfur is removed as SO, and impurities are slagged off.

air intake

a. The airway or airways through which fresh air is brought into a mine.

b. A device for supplying a compressor with clean air at the lowest possible temperature.

air jig

A machine in which the feed is stratified by means of pulsating currents of air and from which the stratified products are separately removed.

air lancing

a. Removing or cutting away loose material by means of compressed air, using an air lance; airblasting.

b. In founding, a cleaning operation, as cleaning sand from molds and castings, using an air lance; airblasting. c. Opening passages for molten materials.

air leakage

a. The short-circuiting of air from intake to return airways (through doors, stoppings, wastes, and old workings) without doing useful work in flowing around the faces. The total air leakage is usually within the range of 35% to 53% of that passing through the surface fan.

b. The air that escapes from compressed-air lines by leakage from joints, valves, hoses, etc.

air leg

a. A cylinder operated by compressed air, used for keeping a rock drill pressed into the hole being drilled.

b. A device, incorporating a pneumatic cylinder, providing support and thrust for a jackhammer.

air-leg support

An appliance to eliminate much of the labor when drilling with handheld machines. It consists of a steel cylinder and air-operated piston, the rod of which extends through the top end of the cylinder and supports the drilling machine. The air leg and machine can be operated by one worker. Syn: pneumatic drill leg.

air level

Eng. A level or airway (return airway) of former workings used in subsequent deeper mining operations for ventilation.

air lift

An apparatus used for pumping water from wells either temporarily or for a permanent water supply; for moving corrosive liquids such as sufuric acid; for unwatering flooded mines; for elevating mill tailings, sands, and slimes in cyanide plants; and for handling the feed to ball mills. In operation, compressed air enters the eduction pipe and mixes with the water. As the water and air rise, the air expands and is practically at atmospheric pressure at the top of the discharge pipe. The efficiency of the air lift is calculated on the basis of the foot-pounds of work done in lifting the water, divided by the isothermal work required to compress the air.

air-lift dredge

Dredge in which solids suspended in a fluid are lifted. By injecting air into a submerged pipe beneath the water surface, the density of the fluid column inside the pipe can be lessened, forcing the fluid column to rise in the tubular pipe. Syn: airlift sampler.

airlift sampler

See: air-lift dredge.

air-line lubricator

See: line oiler.

airline respirator

An atmosphere-supplying respirator in which the respirable-gas supply is not designed to be carried by the wearer (formerly called supplied-air respirator).

air lock

a. A casing at the top of an upcast shaft to minimize surface air leakage to the fan. It consists of a large double casing enveloping the whole of the upcast-shaft top and extending into the headgear. Some are fitted with power-operated doors and allow high-speed winding with little leakage. A modern light-alloy structure raised through spring-loaded attachments by the top of the cage on ascending has proved efficient. Syn: shaft casing.

b. A system of doors arranged to allow the passage of workers or vehicles without permitting appreciable airflow.


A worker who constructs brattices. Syn: brattice worker.

air mat

A mat made of porous material, usually canvas, and used to subdivide and distribute air in certain pneumatic-type flotation machines.

air mover

A portable compressed-air appliance, which may be used as a blower or exhauster. It converts the compressed air into a large induced volume of moving air. The compressed air is fed through a side inlet and is expanded at a high velocity through an annular orifice. It is useful for emergency ventilation in workings where auxiliary fans cannot be installed. Syn: injector; static air mover. See also: auxiliary ventilation.

air-operated winch

A small, compressed-air drum haulage or hoist used for lifting, dragging, or skidding work in mines. With capacities ranging from 660 to 4,400 lb (300 to 2,000 kg), these winches have powerful piston motors and are capable of continuous operation. They are easy to move from job to job and are used for shaft sinking and moving wagon drills at quarry and opencast operations.

air photograph

See: aerial photograph.

air pit

See: air shaft.

airplane-strand wire rope

A small 7- or 19- wire galvanized strand made from plow steel or crucible-steel wire.

air-power-operated mine door

Mine doors help to keep the air flow in shafts and mine working areas constant. In cases of explosions, doors "give" to relieve the pressure, then close automatically. The doors are mobile and can be set up in any location. They are opened and closed by a compressed-air cylinder and are designed to be used where haulage equipment operates on a trolley wire.

air pressure

a. For rock drills, the air pressure ranges from 70 to 90 psi (480 to 620 kPa), the most economical pressure for such machines being from 90 to 95 psi (620 to 655 kPa), when high drilling speed is attained.

b. To operate the percussive tool and to flush the hole of cuttings, surface mounted drills use 690 to 1,725 kPa air pressure.

air-pressure drop

The pressure lost or consumed in overcoming friction along an airway.

air propeller

A rotating set of blades designed to impart momentum to an air mass.

air pump

A pump for exhausting air from a closed space or for compressing air or forcing it through other apparatus. CF: vacuum pump.

air-purifying respirator

A respirator in which ambient air is passed through an air-purifying element that removes the contaminants. Air is passed through the air-purifying element by means of the breathing action or by a blower.

air quantity

The amount of air flowing through a mine or a segment of a mine, in cubic meters per second. Air quantity is the product of the air velocity times the cross-sectional area of the airway. See also: air current. Syn: air volume.

air ramming

A method of forming refractory shapes, furnace hearths, or other furnace parts by means of pneumatic hammers.

air receiver

A vessel into which compressed air is discharged to be stored until required. See also: air-conditioning process.

air-reduction process

See: roasting and reaction process.

air regulator

An adjustable door installed in permanent air stoppings or in an airway without a stopping to control ventilating current.

air requirements

The quantity of air required by law or practical considerations to maintain adequate ventilation of a mine. This quantity will depend on (1) the length of face room in production, (2) the average distance from the shafts to the faces, (3) the gas emission rate, (4) the depth of the workings, and (5) the volumetric efficiency of the mine ventilation. See also: air volume; ventilation planning.

air rig

A drill machine powered by an airdriven motor. CF: air drill.

air rod puller

See: rod puller.

air rotary drilling

Drilling technique that utilizes compressed air to lift the cuttings up the borehole and to cool the bit. Used when possible for environmental monitoring, because no drilling fluids are introduced into the formation. Feasible only in consolidated or semiconsolidated formations.

air-sand process

See: Fraser's air-sand process.

air seal

A method for the prevention of the escape of warm gases from the entrance or exit of a continuous furnace, or tunnel kiln, by blowing air across the opening.

air separation

In powder metallurgy, the classification of metal powders into particle size ranges by means of a controlled airstream.

air separator

A machine for the size classification of the fine ceramic powders, such as china clay; the velocity of an air current controls the size of particle classified.

air set

a. The property of a material to develop high strength when dried; e.g., air-setting mortars.

b. In a material such as a castable refractory, refractory mortar, or plastic refractory, the ability to harden without the application of heat.

air shaft

A shaft used wholly or mainly for ventilating mines, for bringing fresh air to places where miners are working, or for exhausting used air. It may be used as an intake (downcast) shaft or a return (upcast) shaft. See also: downcast; upcast. Syn: air pit.

air shooting

In seismic prospecting, a technique of applying a seismic pulse to the ground by detonating explosive charges in the air.

air shot

A shot prepared by loading (charging) in such a way that an airspace is purposely left in contact with the explosive for the purpose of lessening its shattering effect.

air shrinkage

The volume decrease that a clay undergoes in drying at room temperature.


Slaked by exposure to the air; as lime.


Exposure of quicklime to the atmosphere to give slow hydration.

air slit

York. A short heading driven more or less at right angles to and between two headings or levels for ventilation. See also: stenton.

air slug

A mass of air under compression entrapped in the liquid circulated through a borehole drill string or a liquid-piping system.

air sollar

A compartment or passageway carried beneath the floor of a heading or of an excavation in a coal mine for ventilation. See also: sollar.

air-space ratio

The ratio of a volume of water that can be drained from a saturated soil under the action of force of gravity to a total volume of voids.

air-sparged hydrocyclone

A separator consisting of two concentric right-vertical tubes, a conventional cyclone header at the top, and a froth pedestal at the bottom. The inner tube is a porous-wall tube. The slurry is fed tangentially through the cyclone header to develop a radial swirl flow. Air is sparged through the jacketed, inner porous tube wall and is sheared into small bubbles by the swirl flow. Hydrophobic coal particles in the slurry attach to the air bubbles and report as overflow product. The hydrophilic refuse particles remain wetted and report as underflow product.

air split

The division of the main current of air in a mine into two or more parts. See also: split.

air stack

A chimney formerly used to ventilate a mine.

air stain

Gas trapped beneath mica cleavage surfaces in flattened pockets, tiny bubbles, or groups of closely spaced bubbles.

air starter

A starter used on large coal haulers that permits the elimination of all batteries except the 6-V units for the headlights. These starters are operated by compressed air supplied at 100 psi (690 kPa) from a storage tank on the tractor. Trucks can stand idle for 4 or 5 days and there is still enough air in the tanks to start the engines.

air-stowing machine

The machine used for blowing the stone chippings into the waste area in pneumatic stowing. It consists of a steel paddle wheel revolving in an adjustable casing. Stowing dirt is fed continuously from a hopper to the machine, which in turn blows the material through pipes 5 to 6 in (13 to 15 cm) in diameter into the waste area. See also: pneumatic stowing.

air streak

In mica, a series of air inclusions connected (or nearly connected) to form a relatively long, thin streak. Also known as silver streak.

air survey

In mining, a check on ventilation, gas, and dust in a mine.

air-swept ball mill

See: ball mill.

air-swept mill

A tumbling mill used in dry grinding, from which finished material is removed by means of regulated air currents that can be so controlled as to produce a closed circuit.

air swivel

A device similar to a water swivel but designed to conduct air under compression into a rotating drill stem when air instead of a liquid is used as an agent to flush drill cuttings out of a borehole. CF: water swivel.

air table

A shaking table used when water is scarce to effect gravity concentration of sands. Air is blown upward through a porous deck, over which a layer of finely crushed ore passes. The heavy and light minerals stratify and gravitate to separate discharge zones. Syn: pneumatic table.

air-track drill

A heavy drilling machine for quarry or opencast blasting. It has continuous tracks and is operated by independent air motors. It tows its rotary compressor and drills holes 3 in or 4 in (7.6 cm or 10.2 cm) in diameter at any angle, but it is chiefly used for vertical holes up to 80 ft (24.4 m) in depth.

air transport

A method employed in some mines in which material is transported and stowed pneumatically through pipelines.

air trunk

A large pipe or shaft for conducting air, such as for ventilation or to a furnace.

air tub

The cylinder on a blowing engine that pumps a blast of wind or air.

air turbolamp

A lamp coupled to the compressed air mains, which may be at any pressure between 275 kPa and 700 kPa. It consumes 0.025 m (super 3) /s of free air. The electrical power is produced by a small turboalternator with a six-pole permanent magnet rotor.

air valve

The valve that controls the alternate admission and release of compressed air to each cell of a Baum-type washbox.

air velocity

The rate of motion of air in a given direction; in mine ventilation it is usually expressed in meters per second. This is usually measured conducting a vane anemometer traverse over a selected cross section, the area of which is also measured.

air vessel

A small air chamber fixed to the pipeline on the discharge side of a reciprocating pump that acts as a cushion to minimize the shock produced by the pulsations of the pump.


A device for handling dusty materials, built on the principle of a pneumatic cleaner. The system used is a suction system, whereby the material (soda ash, salt cake, cement, or powdered lime) is drawn from the car through a flexible hose into a vacuum tank designed to recover a large percentage of the dust floating in the air.

air-void ratio

The ratio of the volume of air space to the total volume of voids in a soil mass.

air volume

In mining, the quantity (Q) of air flowing in cubic meters per second. It is obtained by multiplying the average velocity (V) in meters per second by the area (A) of the airway in square meters; i.e., Q = AV. See also: air requirements; air quantity.

air washer

Air washers make use of water sprays or cooling coils for evaporative and sensible cooling of mine air. Their use has largely been limited to shallow coal mines in the United States, where it is desirable to reduce the dry-bulb temperature of the intake air during the hot summer months to prevent slaking of the roof due to excessive expansion. An air washer is essentially a heat exchanger and is similar to the type of unit employed for heat transfer with refrigeration or evaporative-cooling systems.

air wave

The acoustic-energy pulse transmitted through the air as a result of a pressure (sound) source; e.g., explosion, near-surface seismic shot, or supersonic aircraft.


Any underground gallery or passage through which a portion of the ventilation passes; i.e., the air is carried. Syn: air course; wind road.

Airy hypothesis

A concept of the mechanism of isostasy, proposed by George Bedell Airy, that postulates an equilibrium of crustal blocks of the same density but of different thickness; thus the topographically higher mountains would be of the same density as other crustal blocks but would have greater mass and deeper roots. CF: Pratt hypothesis.


A high-strength, high-density, gelatinous permitted explosive having good water resistance; used for dry and wet conditions both in rock and in the breaking of hard coal. See also: Polar Ajax.


A pale-yellow to dark reddish brown, sulfur-bearing fossil resin found in brown coal. Also spelled ajkite.


Roman term designating size of water delivery pipes and outlet spouts. Syn: adjutage.


A tetragonal mineral, ferric oxyhydroxide beta-FeO(OH,Cl) ; rust colored; occurs in soils.


A hexagonal mineral (epsilon-MnO (sub 2) ), trimorphous with pyrolusite and ramsdellite. See: pyrolusite.

Akins' classifier

Used for separating fine-size solids from coarser solids in a wet pulp; consists of an interrupted-flight screw conveyor operating in an inclined trough.


A monoclinic mineral, Mn (sub 4) Mg(AsO (sub 4) ) (sub 2) .4H (sub 2) O ; forms reddish-brown rounded aggregates.


An orthorhombic mineral, MgB (sub 6) O (sub 7) (OH) (sub 6) .2H (sub 2) O.


An isometric mineral, manganese sulfide, MnS ; iron-black; in epithermal vein deposits; an ore of manganese. Formerly called alabandine. Syn: manganblende; manganese glance.


A massive form of gypsum; very fine grained; commonly snow-white and translucent but may be delicately shaded or tinted with light-colored tones. Because of its softness, it can be easily carved and polished. Widely used for ornamental purposes. Chemically it is CaSO (sub 4) .2H (sub 2) O . It is a beautifully banded form of stalagmitic calcite occurring in Algeria and in Egypt. Syn: oriental alabaster; onyx marble.


Impure ozokerite containing an admixture of country rocks and found in the region of the Caspian Sea.


A monoclinic mineral, PbSiO (sub 3) . Syn: lead silicate; lead metasilicate.


In the United States, a commonly used term for a granitic rock containing few, if any, dark minerals. The term is used to designate granitoid rocks in which quartz constitutes 20% to 60% of the felsic minerals and in which the ratio of alkali feldspar to total feldspar is greater than 90%; i.e., the equivalent of alkali granite. Alaskite is a commercial source of feldspar near Spruce Pine, NC. CF: aplogranite.


A dark brown to black asphaltic pyrobitumen with conchoidal fracture occurring as veins 1 to 16 ft (0.3 to 4.9 m) wide in the Albert Shale of Albert County, NB, Can. It is partly soluble in turpentine, but practically insoluble in alcohol. It was earlier called albert coal.

albert shale

An early name for albertite.


a. A triclinic mineral, NaAlSi (sub 3) O (sub 8) ; feldspar group, with up to 10 mol % CaAl replacing NaSi; a member of the plagioclase and the alkali feldspar series; prismatic cleavage; a common rock-forming mineral in granite, intermediate to felsic igneous rocks, low-temperature metamorphic rocks, and hydrothermal cavities and veins; can be used as a glaze in ceramics.

b. The pure sodium-feldspar end member in the plagioclase series. Syn: sodium feldspar; white feldspar; white schorl.

albite-epidote-amphibolite facies

The set of metamorphic mineral assemblages (facies) in which basic rocks are represented by hornblende + albite + epidote. Equivalent to Eskola's epidote-amphibolite facies, it is of uncertain status, transitional between the greenschist facies and the amphibolite facies. It is generally believed to be favored by the higher pressures of regional metamorphism.

albite porphyrite

See: albitite.


A porphyritic igneous rock, containing phenocrysts of albite in a groundmass chiefly consisting of albite. Muscovite, garnet, apatite, quartz, and opaque oxides are common accessory minerals. Syn: albitophyre; albite porphyrite.


Introduction of, or replacement by, albite, usually replacing a more calcic plagioclase.


See: albitite.


A kaolinitic clay found in Dorsetshire, England. It is used as a low-percentage addition to natural molding sands.


The immature chemistry of the Middle Ages, characterized by the pursuit of the transmutation of base metals into gold, and the search for the alkahest and the panacea.


C (sub 2) H (sub 5) OH ; made from grain. Not to be confused with methyl hydroxide or methanol. Syn: ethanol.

alexandrine sapphire

Incorrect name for alexandritelike sapphire; also for so-called synthetic alexandrite.

alexandrite effect

The property of some chrysoberyl and other minerals and stones to appear green in sunlight, but red under incandescent illumination.

alexandritelike tourmaline

See: chameleonite.


A waxlike resin from Kaluga, Russ, which resembles compact turf. Also spelled alexjejevite.


Photosynthetic, almost exclusively aquatic, plants of a large and diverse division (Algae) of the thallophytes, including seaweeds and their fresh-water allies. It ranges in size from simple unicellular forms to giant kelps several meters long, and displays extremely varied life-cycles and physiological processes, with, e.g., different complexes of photosynthetic pigments. Algae range from the Precambrian. An individual plant is called an alga.


Of, pertaining to, or composed of algae.

algal coal

Coal composed mainly of algal remains, such as Pila, Reinschia, etc. Also called boghead coal.

algal limestone

A limestone composed largely of the remains of calcium-carbonate-producing algae, or one in which such algae bind together the fragments of other calcium-carbonate-producing forms.

algal reef

An organic reef in which algae are or were the principal organisms producing calcium carbonate, e.g., off the coast of Bermuda. The reefs may be up to 10 m high and more than 15 m across.

algal stromatolite

See: stromatolite.


A general term for a bitumen derived from algae.

alga sapropel

Equivalent to peat of the humic coal series.

Algerian onyx

See: oriental alabaster.


Designates the characteristic maceral of boghead coal. In reflected light it is very difficult to recognize the cellular structure of the algae. The reflecting power of the maceral is much weaker than that of vitrinite and is also weaker than that of sporinite in coals of low rank. In transmitted light, alginite sometimes shows structure (of colonies of algae). The color is yellow to orange. Alginite is best recognized by luminescent microscopy; it shows marked luminescence of varying color--silvery blue, green, yellowish brown. The humic constituents either are not luminescent or show a different kind of luminescence to the alginite. Syn: algite.


The constituent petrological unit, or maceral, of algal material present in considerable quantity in algal or boghead coal. See also: alginate.


a. Arsenide of copper occurring as a white incrustation in the Algodona silver mine, Chile.

b. An orthorhombic mineral, Cu (sub 6) As ; pseudohexagonal.

Algoman orogeny

Orogeny and accompanying granitic emplacement that affected Precambrian rocks of northern Minnesota and adjacent Ontario about 2.4 billon years ago; it is synonymous with the Kenoran orogeny of the Canadian classification.


a. In mine surveying, a movable arm used to read horizontal angular distances.

b. A device having a level bubble combined with a quarter or a half circle graduated in degrees that is used by drillers to determine the inclination of a drill stem and/or borehole at the collar of the borehole. Also called angle level; angle rule; clinometer; clinometer rule. c. An instrument used in planetable surveying, consisting of a telescope or sighting device pivoted to swing through a vertical graduated arc atop a vertical stand attached to a steel rule, one edge of which is parallel with the sight line of the telescope. d. Sometimes incorrectly used as a syn. for transit; theodolite. e. A rule equipped with simple or telescopic sights, used for determining the directions of objects, specif., a part of a surveying instrument consisting of a telescope or other sighting device, with index and reading or recording accessories. f. A surveying instrument used with a planetable for mapping; e.g., peep-sight alidade and telescopic alidade.

alien filling

Filling material brought from the surface or from some place other than the mine.


a. To position a drill so that its drill stem is centered on a point and parallel to a predetermined angle and compass direction. Also called line in; lineup.

b. To reposition a drill and bring its drill stem over the center and parallel with a newly collared drill hole.


a. The planned direction of a tunnel or other roadway driven irrespective of coal seam or orebody structure; the planned direction of longwall panels or face lines.

b. Formation or position in line, or, more properly, in a common vertical plane. c. The laying out of the axis of a tunnel by instrumental work. d. See: coplaning. e. In railway or highway surveying, the ground plan, showing the alignment or direction of the route to be followed, as distinguished from a profile, which shows the vertical element. f. The act of laying out or regulating by line; adjusting to a line.

alinement clamp

A setscrew-equipped, universal-type clamp from one side of which a slotted angle-iron wand, about 18 in (45.7 cm) long, extends outward from a clamping device at 90 degrees . May be made to fit any size drill rod and is used in pairs, leapfrog fashion, to orient successive rods in a specific compass direction as these are lowered into a borehole being surveyed by the acid-bottle method. By this means, the bearing and inclination of a drill hole may be determined in formation or under conditions where a Maas- or other-type magnetic compass cannot be used.


Of, relating to, or derived from fat; fatty; acyclic. Applied to a large class of organic compounds characterized by an open-chain structure and consisting of the paraffin, olefin, and acetylene hydrocarbons and their derivatives (as the fatty acids).


A discredited term referring to massive apple-green, hydrated magnesium-nickel silicate similar to genthite.


A massive, deep indigo-blue copper-lead sulfide, Cu (sub 2) S.PbS . It contains 53.63% copper and 28.25% lead. Tarnishes quickly.

Aliva concrete sprayer

A compressed-air machine for spraying concrete on the roof and the sides of mine roadways. Used in coal mines for the fireproofing of roadways, for reducing air leakages, and for spraying tunnels supported by roof bolts. See also: guniting; gunite.


Said of coal when it makes a rustling sound as it bursts, cracks, and breaks off while under pressure. The rising of methane from the coal causes a similar sound. CF: dead.


a. Any strongly basic substance, such as a hydroxide or carbonate of an alkali metal (e.g., sodium, potassium). Plural: alkalies. Adj. alkaline; alkalic. Said of silicate minerals that contain alkali metals but little calcium; e.g., the alkali feldspars.

b. Any substance having marked basic properties; i.e., being capable of furnishing to its solution or other substances the hydroxyl ion, OH (super -) .

alkali bentonite

A bentonite containing easily exchangeable alkali cations and having original properties that are not permanently destroyed by the action of sulfuric acid, but can be restored by treatment with an alkali salt followed by regulated dialysis. This group includes Wyoming-type bentonite and other similar bentonites.


a. Said of an igneous rock that contains more alkali metals than is considered average for the group of rocks to which it belongs.

b. Said of an igneous-rock series that contains more sodium and/or potassium than is required to form feldspar with the available silica. c. Said of an igneous-rock series containing less than 51% silica when the weight percentages of CaO and of K (sub 2) O + Na (sub 2) O are equal. d. Said of an igneous rock belonging to the Atlantic suite. Syn: alkali; alkaline.

alkalic feldspar

See: alkali feldspar.

alkali earth

One of a group of elements (Group II) forming divalent cations; esp. calcium, strontium, and barium, but also includes beryllium, magnesium, and radium.

alkali feldspar

a. Those feldspars composed of mixtures or crystal solutions of potassium feldspar, KAlSi (sub 3) O (sub 8) , and sodium feldspar, NaAlSi (sub 3) O (sub 8) , with little or no calcium feldspar, CaAl (sub 2) Si (sub 2) O (sub 8) .

b. The subgroup of the feldspar group including albite, anorthoclase, microcline, orthoclase, and sanidine. Syn: alkalic feldspar. CF: plagioclase.

alkali flat

A level area or plain in an arid or semiarid region, encrusted with alkali salts that became concentrated by evaporation and poor drainage; a salt flat. See also: playa.

alkali garnet

A general term for members of the sodalite group that are closely related crystallographically and chemically to the true garnets.

alkali granite

a. A coarse-grained, plutonic rock carrying free quartz and alkali feldspar.

b. A granitoid rock with accessory sodic amphibole or sodic pyroxene.

alkali-lime series

Igneous rocks that contain soda-lime (plagioclase) feldspars.

alkali metal

A metal in group IA of the periodic system; namely, lithium, sodium, potassium, rubidium, cesium, and francium. They form strong alkaline hydroxides; hence, the name. Syn: alkaline metal.


a. An apparatus for measuring the strength or the amount of alkali in a mixture or solution.

b. An apparatus for measuring the amount of carbon dioxide (as that liberated from a weighed sample of carbonate-containing material by reaction with acid).


Adj. of alkali. See: alkalic.

alkaline-earth bentonite

A bentonite containing easily exchangeable alkaline-earth cations and, either before or after acid treatment, capable of being made to assume properties of an alkali bentonite by treatment with an alkali salt followed by regulated dialysis.

alkaline-earth metal

A metal in group IIA of the periodic system; namely, beryllium, magnesium, calcium, strontium, barium, and radium; so called because the oxides or earths of calcium, strontium, and barium were found by the early chemists to be alkaline in reaction.

alkaline metal

See: alkali metal.


The extent to which a material exhibits the property of yielding hydroxyl ions in a water solution. See also: pH.

alkali soil

A saline soil having 15% or more exchangeable sodium.

alkali subbentonite

A bentonite containing easily replaceable alkali bases but having original properties that are destroyed by acid treatment.


A member of the paraffin series, such as methane, ethane, etc.


A member of the hydrocarbon group series (CnH (sub 2) n); e.g., ethylene, propylene.


A discredited term referring to a compound of lead, copper, bismuth, and sulfur.


One of a group of organic compounds containing a carbon-to-carbon triple bond; e.g., acetylene, allylene. Also spelled alkine.


A monoclinic mineral, Mn (sub 7) (AsO (sub 4) ) (sub 2) (OH) (sub 8) ; vitreous; resembles the axinites. Also spelled allaktit.


A heavy dull-red or green altered carbonated rhodonite. Syn: diaphorite.


A monoclinic mineral, 2[(Ca,Y,Ce) (sub 2) (Fe,Al) (sub 3) O(OH)(Si (sub 2) O (sub 7) )(SiO (sub 4) )] ; epidote group; massive, pitchy, slightly radioactive, and metamict; a minor accessory in felsic igneous rocks and pegmatites. Formerly called orthite; cerine; bucklandite; treanorite. Syn: yttro-orthite.


A mineral, Ag (sub 1-x) Sb (sub x) with x=0.09 to 0.16.


Former name for a variety of goethite.


A monoclinic mineral, Mn (sub 5) (SiO (sub 4) ) (sub 2) (OH) (sub 2) ; humite group; dimorphous with ribbeite; in skarns.


A mixture of stibarsen, SbAs , and arsenic or antimony. Syn: arsenical antimony. CF: antimonial arsenic.

Allen cone

A conical tank used in mineral flotation to separate sand from slime using a float-controlled spigot on peripheral overflow. See also: cone classifier.

Allen-O'Hara furnace

A horizontal, double-hearth furnace for calcining sulfide ores.


See: rectorite.

alley stone

See: aluminite.


Said of minerals that have an odor of garlic when rubbed, scratched, or heated; e.g., arsenical minerals.


a. See: safety clamp.

b. Any of several types of machines for metalworking, rock crushing, etc., in which work is accomplished by two massive jaws, one or both of which move as, e.g., alligator shears (preferably, lever shears) or an alligator crusher (preferably, lever crusher). c. A prolonged, steel hingelike device by means of which the abutting ends of a flat drive belt can be fastened or laced together.

all-mine pig

Iron smelted entirely from raw ore.


A collective term introduced by Folk (1959) for one of several varieties of discrete and organized carbonate aggregates that serve as the coarser framework grains in most mechanically deposited limestones, as distinguished from sparry calcite (usually cement) and carbonate-mud matrix (micrite). Important allochems include silt-, sand-, and gravel-size fragments torn up and reworked from the deposit; ooliths; pellets; lumps; and fossils or fossil fragments (carbonate skeletons, shells, etc.). Syn: allochemical.


See: allochem.


a. A calcium-chromium garnet.

b. A reddish brown variety of andradite garnet.


a. Descriptive of crystals that exhibit electrical conductivity under the influence of light.

b. A gem stone with a coloring agent extraneous to its chemical composition. Opposite of idiochromatic. c. Color produced by a chromophore that is not essential to mineral composition.

allochromatic mineral

Mineral that would be colorless if chemically pure, but which commonly exhibits a range of colors due to the presence of small quantities of one or more coloring elements. Chief among these elements are those having atomic numbers 22 to 29; namely, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper. Corundum, beryl, spinel, and quartz are examples of allochromatic gemstones. See also: idiochromatic mineral.


a. A mass of rock that has been moved from its place of origin by tectonic processes, as in a thrust sheet or nappe. Many allochthonous rocks have been moved so far from their original sites that they differ greatly in facies and structure from those on which they now lie. Ant. autochthon. Syn: allochthonous. Also spelled allochthone.

b. A mass of redeposited sedimentary materials originating from distant sources.


a. Originated by Gumbel and applied to rocks, the dominant constituents of which have not been formed in place. CF: autochthonous.

b. Coal formation according to the drift theory. c. Formed or produced elsewhere than in its present place; of foreign origin, or introduced. The term is widely applied; e.g., to coal or peat that originated from plant material transported from its place of growth, or to an allochthon on a low-angle thrust fault. The term is similar in meaning to allogenic, which refers to constituents rather than whole formations. Ant. autochthonous. See also: allochthon.

allochthonous coal

Coal originating from accumulations of plant debris that have been transported from their place of growth and deposited elsewhere. The debris can be differentiated as coming from near or from far, and likewise whether it represents recent (dead or still living) or already fossilized material. Syn: drift coal. See also: drift theory.

allochthonous peat

Drift peat of lacustrine character. It is subdivided into Gyttja type and Dry type.


A monoclinic mineral (Co,Fe)AsS ; steel gray; dimorphous with glaucodot. Formerly called alloclase.

alloclastic breccia

See: volcanic breccia.


Generated elsewhere; applied to those constituents that came into existence outside of, and previously to, the rock of which they now constitute a part; e.g., the pebbles of a conglomerate. CF: authigenic.


See: herderite.


Of the same crystalline form but of different chemical composition. Syn: isomorphous. CF: allomorphous.


a. Syn: paramorph (obsolete); pseudomorph.

b. A polymorph or dimorph. Adj. allomorphous.


Changes produced in minerals without gain or loss of components; e.g., the change from kyanite to sillimanite. See also: paramorphism.


Obsolete term for barite, esp., pseudomorphous after anhydrite.


Of the same chemical composition but of different crystalline form. CF: allomeric.


a. A nearly silver-white palladium, found in hexagonal plates in the Harz Mountains, Germany.

b. Former name for stibiopalladinite. c. Palladium crystallizing in the hexagonal system (as opposed to isometric palladium).


a. Al (sub 2) O (sub 3) .SiO (sub 2) .nH (sub 2) O . A clay mineral composed of hydrated aluminosilicate gel of variable composition; P (sub 2) O (sub 5) may be present in appreciable quantity. Syn: riemannite.

b. A mineral gel, amorphous hydrous aluminum silicate; soft; has pale tints; in soils developed from volcanic glass and ash. It changes from glassy to earthy upon dehydration.


An obsolete syn. of allophane.


Clays of the allophane, halloysite, and montmorillonite groups.


A constituent of a metamorphic rock which, in the new rock, has not changed its original crystal outlines.


See: xenomorphic.


See: xenomorphic.


Applied by Berzelius to those substances that exist in two or more forms, such as diamond and graphite. See also: polymorphism.


See: allotropy.


a. The existence of a substance, esp. an element, in two or more different modifications usually in the same phase, such as different crystalline forms of carbon, iron, phosphorus, and sulfur.

b. Polymorphism in a chemical element; e.g., isometric and hexagonal carbon (diamond and graphite), monoclinic and orthorhombic sulfur (rosickyite and sulfur). An allotrope is one of the crystal forms. Syn: allotropism. Adj. allotropic.

allowable bearing value

The maximum pressure that can be permitted on foundation soil giving consideration to all pertinent factors, with adequate safety against rupture of the soil mass or movement of the foundation of such magnitude that the structure is impaired. Also called allowable soil pressure.

allowable pile-bearing load

The maximum load that can be permitted on a pile with adequate safety against movement of such magnitude that the structure is endangered.

allowable stress

If a member is so designed that the maximum stress as calculated for the expected conditions of service is less than some certain value, the member will have a proper margin of security against damage or failure. This certain value is the allowable stress, of the kind, and for the material and condition of service in question. The allowable stress is less than the "damaging stress" because of uncertainty as to the conditions of service, nonuniformity of material, and inaccuracy of stress analysis. The margin between the allowable stress and the damaging stress may be reduced in proportion to the certainty with which the conditions of service are known, the intrinsic reliability of the material, the accuracy with which the stress produced by the loading can be calculated, and the degree to which failure is unattended by danger or loss. CF: factor of safety. Syn: working stress.


A substance having metallic properties, and composed of two or more chemical elements, of which at least one is a metal.


The act or process of alloying; specif., in minting, of alloying the precious metals with baser ones to form a harder alloy.

alloy sludger

A laborer who salvages sludge from furnace pots for use in recovery of metals. Also called sludger.

alloy system

All the alloys that can be made by mixing two metals from a binary alloy system, three metals from a ternary alloy system, and so on. The limits of temperature and composition within which the constituents in a system are stable are represented by the constitutional diagram.


a. A monoclinic mineral, Na,Ca)Fe (super +2) (Mn,Fe (super +2) ,Fe (super +3) ,Mg) (sub 2) (PO (sub 4) ) (sub 3) ; alluaudite group; forms a series with ferroalluaudite; in pegmatites.

b. The mineral group alluaudite, caryinite, ferroalluaudite, hagendorfite, maghagendorfite, and varulite.


Seldom-used plural of alluvium.


a. Said of a placer formed by the action of running water, as in a stream channel or alluvial fan; also said of the valuable mineral, e.g., gold or diamond, associated with an alluvial placer.

b. Pertaining to or composed of alluvium, or deposited by a stream or running water; e.g., an alluvial clay or an alluvial divide.

alluvial clay

A clay that has been deposited by water on land, usually in association with rivers or streams.

alluvial cone

An alluvial fan with steep slopes; it is generally higher and narrower than a fan, and is composed of coarser and thicker material believed to have been deposited by larger streams. The term is sometimes used synonymously with alluvial fan. CF: alluvial fan. Syn: debris cone; dry delta; wash.

alluvial deposit

See: alluvium.

alluvial fan

A low, outspread, gently sloping mass of loose rock material, shaped in plan view like an open fan or a segment of a cone; deposited by a stream (esp. in a semiarid region) at the place where it issues from a narrow mountain valley upon a plain or broad valley, or where a tributary stream is near or at its junction with the main stream, or wherever a constriction in a valley abruptly ceases or the gradient of the stream suddenly decreases; it is steepest near the mouth of the valley where its apex points upstream, and it slopes gently and convexly outward with gradually decreasing gradient. CF: alluvial cone; bajada. Syn: fan; detrital fan; talus fan; dry delta.

alluvial flat

A small alluvial plain bordering a river, on which alluvium is deposited during floods. CF: alluvial plain. Syn: river flat.

alluvial mining

The exploitation of alluvial deposits by dredging, hydraulicing, or drift mining. See also: placer mining.

alluvial ore deposit

See: placer.

alluvial plain

A level or gently sloping tract or a slightly undulating land surface produced by extensive deposition of alluvium, usually adjacent to a river that periodically overflows its banks; it may be situated on a flood plain, a delta, or an alluvial fan. CF: alluvial flat. Syn: wash plain; river plain; bajada.

alluvial slope

A surface underlain by alluvium, which slopes down and away from the sides of mountains and merges with a plain or a broad valley floor; an alluvial surface that lacks the distinctive form of an alluvial fan or a bajada. See also: bajada.

alluvial tin

Stream tin, or cassiterite pebbles in the gravel along the courses of valleys and rivers on the bedrock. Generally, the purest tin ore. See: stream tin.

alluvial values

In placer mining, the minerals recoverable from the alluvium. These include cassiterite, gold, diamond, gemstones, zirconia, rutile, monazite, and platinum.


a. The deposition or formation of alluvium or alluvial features (such as cones or fans) at places where stream velocity is decreased or streamflow is checked; the process of aggradation or of building up of sediments by a stream along its course, or of covering or filling a surface with alluvium.

b. A hydraulic effect on solids suspended in a current of water, whereby the coarsest and heaviest particles are the first to settle out, and the finest muds the last, as gradient or velocity of a stream is decreased.


See: alluvium.


a. A general term for clay, silt, sand, gravel, or similar unconsolidated detrital material, deposited during comparatively recent geologic time by a stream or other body of running water, (1) as sediment in the bed of the stream or on its flood plain or delta, (2) as a cone or fan at the base of a mountain slope; esp., such a deposit of fine-grained texture (silt or silty clay) deposited during time of flood. Syn: alluvial deposit; alluvion.

b. A driller's term for the broken, earthy rock material directly below the soil layer and above the solid, unbroken bed or ledge rock. Etymol: Latin alluvius, from alluere, to wash against. Plural: alluvia; alluviums.


Sp. A deep-red ocher originally from Andalusia, Spain, similar to Indian red. Used as a pigment and in polishing glass and metals. Also spelled almagre.


a. An isometric mineral, 8[Fe (sub 3) (super 2+) Al (sub 2) Si (sub 3) O (sub 12) ] ; pyralspilite subgroup of the garnet group, with Fe replaced by Mg, Mn, and Ca; in red to brownish-black dodecahedral and trapezohedral crystals, or massive; Mohs hardness, 7-1/2; occurs in medium-grade metamorphic rock and felsic igneous rocks; used as a gemstone and an abrasive. Formerly called almandite; alamandine; almond stone.

b. A violet or mauve variety of ruby spinel; a reddish-purple to purplish-red spinel. c. A reddish-purple sapphire (almandine sapphire).

almandine ruby

A violet-colored magnesium spinel. Syn: ruby spinel.


Former spelling of almandine.

almeria ore

A Spanish hematite.

almond furnace

A furnace in which the slags of litharge left in refining silver are reduced to lead by being heated with charcoal.

almond stone

Former name for almandine.


A lamprophyre chiefly composed of biotite or phlogopite and melilite as essential minerals, commonly with olivine, calcite, and clinopyroxene. Perovskite, apatite, nepheline, and garnet may be present. Its name (Rosenbusch, 1887) is derived from Alnoe, Sweden. Also spelled allnoeite; alnoeite.


Trade name for fused crystalline alumina or artificial corundum used as an quartz and beta quartz.

b. Adj. Of or relating to one of two or more closely related minerals and specifying a particular physical structure (esp. a polymorphous modification); specif. said of a mineral that is stable at a temperature lower than those of its beta and gamma polymorphs (e.g., "alpha cristobalite" or "alpha -cristobalite," the low-temperature tetragonal phase of cristobalite). Some mineralogists reverse this convention, using alpha for the high-temperature phase (e.g., "alpha carnegieite," the isometric phase of carnegieite stable above 690 degrees C). c. In crystallography the angle between the b and c axes.

alpha alumina

A white, anhydrous, nonhygroscopic powder, Al (sub 2) O (sub 3) , produced when precipitated Al(OH), is calcined at 1,000 degrees C. It is the natural product of the Bayer process and other processes used (or proposed) to treat bauxite, clay, or other aluminum-bearing materials.

alpha celsian

A silicate of aluminum and barium, BaAl (sub 2) Si (sub 2) O (sub 8) . An artificial feldspar, similar to anorthite, but containing barium instead of calcium. Hexagonal prisms. Uniaxial, negative.

alpha chalcocite

See: digenite.

alpha hyblite

A porcelain-white, hydrous acidic sulfosilicate of thorium with some uranium, iron, and lead; isotropic. An alteration product of thorite. From Hybla, ON, Can.

alpha mercuric sulfide

See: vermilion.

alpha quartz

A quartz polymorph stable below 573 degrees C; a common constituent of crustal rocks. Syn: low quartz.

alpha zinc sulfide

Colorless when pure; hexagonal; ZnS; mol wt., 97.43; sp gr, 3.98 to 4.1; Mohs hardness, 3.5 to 4.0; luster, resinous; transformation temperature from beta zinc sulfide to alpha zinc sulfide, 1,020+ or -5 degrees C: sublimes at 1,180 degrees C or 1,185 degrees C; melting point, 1,850 degrees C (at 150 atm); insoluble in water and in acetic acid; and very soluble in other acids. Occurs as the brownish-black mineral wurtzite, which is unstable compared with its stable dimorph, the mineral sphalerite (beta zinc sulfide), to which it inverts during alteration and from which it is formed by heating sphalerite to the transformation temperature. Can be crystallized from acid solutions above 250 degrees C. See also: wurtzite; zinc sulfide. CF: beta zinc sulfide.


a. Pertaining to, characteristic of, or resembling the European Alps or any lofty mountain or mountain system, esp. one modified by intense glacial erosion. Spelled Alpine when referring specif. to European Alps.

b. Characteristic or descriptive of the mountainous regions lying between timberline and snowline; said of the climate, flora, relief, ecology, etc. Less strictly, pertaining to high elevations and cold climates. c. A general term for topographical and structural features that resemble in grandeur and complexity those of the European Alps, regardless of the age or location of the mountains and features so described.

Alpine diamond

See: pyrite.


A coarse-grained variety of galena used by potters in preparing a green glaze.


A variety of titanite containing yttria; found in Sweden.


A triclinic mineral, BaCa(CO (sub 3) ) (sub 2) ; pseudo-orthorhombic and trimorphous with barytocalcite and paralstonite. Formerly called bromlite.


An isometric mineral, PbTe ; in veins with gold, sulfides, and other tellurides.


Any change in the mineralogic composition of a rock brought about by physical or chemical means, esp. by the action of hydrothermal solutions; also, a secondary, i.e., supergene, change in a rock or mineral. Alteration is sometimes considered as a phase of metamorphism, but is usually distinguished from it because of being milder and more localized than metamorphism is generally thought to be.

altered mineral

A mineral that has undergone chemical change by geologic (esp. weathering or hydrothermal) processes.

altered rock

A rock that has undergone changes in its chemical and mineralogic composition since its original formation.

altered stone

a. Said of a stone that has undergone chemical and/or mineralogical changes under geologic processes.

b. Any stone of which the appearance, esp. the color, has been changed by any artificial means whatsoever. For example, heat is often used to improve or alter color. Such change may be either external or internal. See also: treated stone; stained stone.

alternate pillar and stope

See: square-set stoping.

alternate polarity

Arrangement in magnetic separator whereby ore travels alternately through normal concentration and entropy fields, thus stirring attracted material and shaking out entrained nonmagnetics.

alternating-current ampere

Current that will produce heat at the same rate as a direct-current ampere, when flowing through a given ohmic resistance.


A term used in the southwestern United States for a bluff, height, or hill. Etymol: Sp., high ground.


a. Any hydrous, alkali aluminum sulfate mineral, including kalinite, potassium alum, sodium alum, mendozite, tschermigite, and lonecreekite. Syn: potash alum.

b. A former name for kalinite and potassium alum. c. Any salts that are double sulfates of aluminum, chromium, iron, or manganese and one of the alkali metals.

alum cake

A product of the action of sulfuric acid on clay, consisting chiefly of silica and aluminum sulfate.

alum earth

An argillaceous rock, commonly a shale, containing marcasite or pyrite which, as it decomposes, forms sulfuric acid that attacks the shale and produces alum. Many such rocks are carbonaceous. See also: alum shale.


An oxide of aluminum, Al (sub 2) O (sub 3) ; the mineral corundum; an important constituent of clay minerals, Al (sub 2) Si (sub 2) O (sub 5) (OH) (sub 4) , determining their suitability for firebrick and furnace linings. Synthetic alumina is used as the feed material in aluminum smelters; it is also used in the preparation of paints called lakes, in dyeing, and in calico printing; in granular form it is used for abrasives and grinding or cutting tools of high tensile strength. Most alumina is made via the Bayer process from hydrated aluminum oxides, as found in bauxite, diaspore, and gibbsite. Aluminum oxide can also be made in an electric furnace by fusing bauxite or corundum. Suitably doped alumina is the feed material for boules of synthetic ruby and sapphire made by the Verneuil flame-fusion process. Fused alumina is crushed and used as an abrasive, a refractory, a heating element for electrical heaters, and as a filtering medium.


A compound having the general formula, MAlO (sub 2) or M (sub 3) AlO (sub 3) , in which M indicates a monovalent metal. Mineral aluminates, such as MgAl (sub 2) O (sub 4) , are termed spinels.

alumina trihydrate

A (sub 2) O (sub 3) .3H (sub 2) O or Al(OH) (sub 3) ; monoclinic; white; crystalline powder, balls, or granules; sp gr, 2.42; obtained from bauxite and used as a source of aluminum.


A monoclinic mineral, Al (sub 2) (SO (sub 4) )(OH) (sub 4) .7H (sub 2) O ; pseudo-orthorhombic, formerly called websterite. Syn: alley stone; argil.

aluminosilicate refractory

A general term that includes all refractories of the fireclay, sillimanite, mullite, diaspore, and bauxite types.

aluminous abrasive

An abrasive produced by fusing aluminum oxide.

aluminous ore

Ore in which the gangue consists principally of alumina.


A light, silvery-white, ductile metal with high electrical conductivity and good resistance to corrosion. Obtained from bauxite. Symbol, Al. It is the lightest of the metals in general use commercially and is the basis for light alloys used in the construction of modern aircraft and rockets; aluminum coatings are used for telescope mirrors, decorative paper, packages, and toys. The oxide, alumina, occurs naturally as ruby, sapphire, corundum, and emery.

aluminum detonator

See: Briska detonator.

aluminum silicates

Varying proportions of Al (sub 2) O (sub 3) and SiO (sub 2) . Occur naturally in clays. Used in the glass and ceramics industry.


See: alunite.


A variety of opal with alumina and lime as impurities.


An amorphous aluminum hydroxide that is a constituent of bauxite. Formerly called cliachite, diasporogelite, and sporogelite.

alum rock

See: alunite.

alum salt

Natural salt from which alum can be made. See also: halloysite; kaolinite.

alum schist

See: alum shale.

alum shale

An argillaceous, often carbonaceous, rock impregnated with alum, originally containing iron sulfide (pyrite, marcasite) which, when decomposed, formed sulfuric acid that reacted with the aluminous and potassic materials of the rock to produce aluminum sulfates. Syn: alum earth; alum schist; alum slate.

alum slate

See: alum shale.


a. A trigonal mineral, KAl (sub 3) (OH) (sub 6) (SO (sub 4) ) (sub 2) ; massive or disseminated; in pale tints; formed from sulfuric acid acting on potassium feldspar in volcanic regions (alunization), and around fumaroles. Formerly called alumstone, alum rock, alumite.

b. A mineral group including jarosite.


Introduction of, or replacement by, alunite.


A triclinic mineral, Al (sub 2) (H (sub 2) O) (sub 12) (SO (sub 4) ) (sub 3) .5(H (sub 2) O) ; in fibrous masses or crusts; white, tinged yellow to reddish, with sharp acid taste; in acid environments filling crevices in coals, slates, gossans, and fumaroles. Syn: feather alum; hair salt.


A monoclinic mineral, (Zn,Ni)Al (sub 4) (VO (sub 3) ) (sub 2) (OH) (sub 12) .2H (sub 2) O ; forms light-blue-green rosettes in the vanadium deposits of Karatau, Kazakhstan.


The lungs can be thought of as two elastic bags containing millions of little distensible air sacs. These air sacs or alveoli are all connected to the air passages, which branch and rebranch like the twigs of a tree.


A zirconium mineral; a source of hafnium, containing 16% HfO (sub 2) ; tetragonal. Obtained from Alve, Norway.