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

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A gabbro that is composed chiefly of calcic plagioclase (e.g., labradorite) and olivine with little or no pyroxene. Such rocks commonly are speckled like trout. Syn: forellenstein; troutstone.


See: troegerite


See: dopplerite.


A very rare tetragonal mineral, H(UO (sub 2) )(AsO (sub 4) ) (sub ) .4H (sub 2) O ; autunite group; strongly radioactive; lemon-yellow; in veins with walpurgite, zeunerite, uranospinite, pitchblende, and other uranium minerals. Also spelled troegerite.

Troeger's classification

A quantitative mineralogic classification of igneous rocks proposed by E. Troeger in 1935.


An isometric mineral, CoSe (sub 2) ; pyrite group; dimorphous with hastite; violet.


A hexagonal mineral, FeS ; a meteorite mineral related to pyrrhotite, Fe (sub 1-x) S , in terrestrial rocks.

Trojan coal powder

High explosive used in mines.


a. The grooved wheel, fixed in bearings at the end of a trolley pole, pressed upward in rolling contact with the overhead trolley wire to take off the electric current for operating the locomotive or other piece of motorized equipment. A trolley glider is frequently used in place of the wheel, making a sliding contact with the wire. Also called trolley wheel.

b. A low carriage, mounted on wheels, for carrying timber, supplies, and machines underground. See also: trawley; bogie.

trolley conveyor

A series of trolleys supported from or within an overhead track and connected by an endless propelling medium, such as a chain, a cable, or other linkage, with loads usually suspended from the trolley. Trolley conveyors may be designed for single or multiple plane operation. Syn: overhead conveyor; overhead trolley conveyor.

trolley locomotive

a. A mine locomotive operated by electricity drawn from overhead conductors. Small grooved wheels or gliders are held in contact with the conductors, and the current passes down a trolley arm to the motor. It is very efficient where heavy loads are hauled up relatively steep gradients. Generally restricted to intake airways not nearer than 300 yd (274 m) to a working face.

b. A mine locomotive operated by electricity drawn from overhead trolley wires.

trolley voltage

Although not actually set by law, the generally accepted maximum direct current trolley voltage is considered to be 300 V. The use of alternating current voltages above 220 V in mines is usually permitted, provided the conductors are properly insulated and the cables end in suitable terminal boxes.

trolley wire

The means by which power is conveyed to an electric trolley locomotive. It is hung from the roof and conducts power to the locomotive by the trolley pole. Power from it is sometimes also used to run other equipment.

trolley wire guards

Coverings for exposed trolley wires in mines and other locations where transportation power wires are within reaching height and are a constant source of danger to all personnel. Coverings, made of rubber or some other insulating material, guard workers from severe burns or electrocution by direct contact with the wire.


An apparatus for producing a blast of air by means of a falling stream of water, which mechanically carries air down with it, to be subsequently separated and compressed in a reservoir or drum below. See also: water blast. Syn: trompe.


A revolving cylindrical screen used in size classification of coarsely crushed ore, coal, gravel, and crushed stone. The material to be screened is delivered inside the trommel at one end. The fine material drops through the holes; the coarse material is delivered at the other end. Also called, according to its various uses, sizing trommel, washing drum, and washing trommel. Also spelled tromel. See also: revolving screen; rotary breaker; rotary screen; shaking screen.

trommel screen

A screen in which the screening surface is formed into a cylinder or frustum of a cone, mounted upon a rotating shaft or on revolving rollers. See also: revolving screen.

tromp curve

See: ash curve.

tromp cut point

See: partition density.

Tromp distribution curve

A curve showing the float-sink percentage of each density fraction of the feed coal. The quantity of clean coal recovered is plotted against the mean densities of the density fraction. From this curve the specific gravity of separation and the sharpness of the separation can be determined. Such a curve is independent of the coal being washed and is characteristic of a specific coal-washing device.


See: trombe.

tromp error curve

See: error curve.

Tromp process

a. The Tromp process was the first to introduce (about 1938) the use of magnetite suspension in dense-medium washing. The magnetite is ground to about minus 1/250 in (0.1 mm) and added to water. The process makes use of an unstable suspension with horizontal currents of differing densities at intermediate levels. The process operates within the size range 6 to 200 mm and in practice is used for raw coal down to 1/4 in (6.4 mm). It gives a reasonably accurate three-product separation.

b. A dense-medium process that utilizes a rapidly settling suspension of finely powdered magnetite or sintered roasted pyrite. This process may be used on any size of coal from 10 to 1/4 in (254 to 6.4 mm) and for any specific gravity from 1.3 to 1.9. The grain size of the magnetite or pyrite is minus 0.1 mm. The quick settling of the magnetite particles gives a higher specific gravity in the lower layers of the wash box, which makes it possible to obtain three products: clean coal, middlings, and refuse.


A monoclinic mineral, Na (sub 3) (Co (sub 3) ) ((HCO (sub 3) )X2H (sub 2) O ; soft; vitreous; colorless to white; alkaline tasting; in saline lake deposits and desert soils; a major source of sodium compounds from extensive deposits at Searles and Owens Lakes, CA, and in Wyoming, Hungary, Egypt, Africa, and Venezuela. See also: sodium sesquicarbonate.

Trona process

The method used for the separation and the purification of soda ash (anhydrous sodium carbonate), anhydrous sodium sulfate, boric acid, borax, potassium sulfate, bromine, and potassium chloride from brine at Searles Lake, San Bernardino County, CA.


A light-colored plutonic rock composed primarily of sodic plagioclase (esp. oligoclase), quartz, sparse biotite, and little or no alkali feldspar. Its name, given by Goldschmidt in 1916, is derived from Trondhjem, Norway. Also spelled: trondjemite; trondheimite.


See: trondhjemite.


a. A manganoan variety of willemite occurring in large reddish crystals.

b. A previously unresolvable, rapidly etching, fine aggregate of carbide and ferrite produced either by tempering martensite at a low temperature or by quenching a steel at a rate slower than the critical cooling rate. Preferred terminology for the first product is tempered martensite; for the latter, fine pearlite.

troostitic structure

Fine aggregates of ferrite and cementite in steel; emulsified ferrite.

Tro-Pari survey instrument

Trade name of a single-shot borehole surveying instrument combining a compass and inclinometer, which is locked in place by the action of a preset time clock.

tropic pack

A special type of packing to protect explosives from deteriorating when subjected to hot, humid atmospheric conditions, such as in tropical areas. The explosives, after being sealed with paraffin, are packed in cartons, which are then wrapped in waxed paper and also sealed with paraffin. The filled cartons are then placed inside a satchel-type case liner of bitumen-laminated paper reinforced with sisal fiber and completely sealed with a waterproof adhesive.


a. A channel, open or covered, that contains coal or ore being conveyed on a chain or shaker conveyor. The shape of the cross section depends on the type of conveyor involved. See also: tray.

b. A hollow or undulation in a mineral field, or in a mineral working. In geology, synonymous with basin; synclinal. See also: graben. c. The lowest point of a given stratum in any profile through a fold. CF: trough line. d. A line occupying the lowest part of a fold; the line connecting the lowest parts on the same bed in an infinite number of cross sections. See also: trough plane.

trough banding

Rhythmic layering or alignment of minerals in an igneous rock, confined to troughlike depressions and considered to have been produced by currents set up in the magma during cooling.

trough conveyor

A pan conveyor or gravity conveyor.

troughed belt

A belt conveyor in which the carrying side is made to form a shallow trough by means of troughing idlers.

troughed belt conveyor

A belt conveyor with the belt edges elevated on the carrying run to form a trough by conforming to the shape of the troughed carrying idlers or other supporting surface. See also: belt conveyor.

troughed roller conveyor

A roller conveyor having two rows of rolls set at an angle to form a trough over which objects are conveyed. See also: el conveyor.

trough fault

A fault, generally a normal fault, that bounds a graben or other structural depression.


a. A structural section shaped like a wide U; riveted or welded to form a bridge deck with the U-shaped sections turned alternately upwards and downwards.

b. Making repeated dozer pushes in one track, so that ridges of spilled material hold dirt in front of the blade. c. Eng. In Derbyshire, toadstones filling fissures.

troughing idler

A belt idler having two or more rolls arranged to turn up the edges of the belt so as to form the belt into a trough.

troughing rolls

The rolls of a troughing idler that are so mounted on an incline as to elevate each edge of the belt to form a trough.

trough line

a. The line occupying the lowest part of the fold, or, more precisely, the line connecting the lowest parts of the same bed in an infinite number of cross sections. CF: trough.

b. The line joining the trough points of a given stratum.

trough plane

The plane that joins the troughs of a series of beds in a syncline; generally, but not necessarily, the same as the axial plane. See also: trough.

trough vein

A trough-shaped ore deposit formed between sedimentary beds in the troughs of synclinal structures.

trough washer

a. A washer applying the principle of alluviation in troughs.

b. In its simplest form, a trough washer is a sloping wooden trough, 1-1/2 to 2 ft (0.46 to 0.6 m) wide, 8 to 12 ft (2.4 to 3.7 m) long, and 1 ft (0.9 m) deep, open at the tail end, but closed at the head end. It is used to float adhering clay or fine material from the coarser portions of ore or coal. A log washer.


See: troctolite.


A wooden channel for air or water.

troy ounce

One-twelfth of a pound of 5,760 grains (troy pound), or 480 grains. A troy ounce equals 20 pennyweights, 1.09714 avoirdupois oz, or 31.1035 g. It is used in all assay returns for gold, silver, and platinum-group metals.

troy pound

A unit of weight that equals 5,760 grains, 12 tr oz, 240 pennyweights, 13.1657 avoirdupois oz, 0.82286 avoirdupois lb, or 373.2509 g.

troy weight

These are the weights used for precious metals. The equivalents are 24 grains = 1 pennyweight; 20 pennyweights = 1 oz; 12 oz = 1 lb. The troy grain is the same as the avoirdupois grain, but the ounce is larger on the troy scale; 1 tr oz = 31.103 g; 1 avoirdupois oz = 28.35 g.


Any wheeled vehicle, usually self-propelled, used to transport heavy articles or materials. In mining, usually applied to dump and/or bottom-dump semitrailers used to transport mined waste and ore materials. The number of types of these haulage units varies widely from the small 2-st (1.8-t) standard dump truck to the unit with capacity 200 st (181 t) or greater. For larger stripping operations, where the haulage conditions are not too rugged, a diesel tractor pulling a bottom-dump semitrailer of capacity 40 to 60 st (36 to 54 t) is most common. The newer trucks are equipped with power steering, power brakes, torque converters, and automatic transmissions.

truck mixer

A concrete mixer, generally mounted on a lorry, or crawler-type tracks, which mixes concrete during the journey from the batching plant to the construction site.

truck roller

See: track roller.


A mixture of chloraluminite and natroalunite.

true azimuth

The azimuth measured clockwise from true north through 360 degrees .

true bearing

The bearing expressed as a horizontal angle between a geographic meridian and a line on the Earth; esp. a horizontal angle measured clockwise from true north. CF: magnetic bearing.

true depth

The actual depth of a specific point in a borehole measured vertically from the surface in which the borehole was collared. Syn: true vertical depth.

true dip

a. A syn. of dip, used in comparison with apparent dip. Syn: full dip.

b. The angle at which veins, strata, etc., dip, as measured vertically downward from the horizon along a line at right angles to the strike of the veins, strata, etc.; also, the dip of a vein, strata, etc., as determined on oriented core. See also: core orientation; oriented core; apparent dip. c. The maximum angle which an inclined bed makes with a horizontal plane. It is the direction in which water would flow if poured on the smooth upper surface of the bed at the outcrop. Also called dip. See also: level course. d. See: three-dimension dip.

true lode

See: fissure vein.

true middlings

a. See: bone coal.

b. Comparatively high-ash material so nearly homogeneous that its quality cannot readily be improved by crushing and cleaning.

true strain

The integral, over the whole of a finite extension, of each infinitesimal elongation divided by the corresponding momentary length. It is equal to log (sub e) (1 + epsilon ), where epsilon is the strain as ordinarily defined. See also: strain.

true stress

For an axially loaded bar, the load divided by the corresponding actual cross-sectional area. It differs from the stress as ordinarily defined because of the change in area due to loading. See also: stress.

true vein

An occurrence of ore, usually disseminated through a gangue of veinstone, and having more or less regular development in length, width, and depth. See also: vein; fissure vein.

true vertical depth

See: true depth.

true whiting

A finely divided calcium carbonate prepared by wet grinding and levigating natural chalk; a variety of limestone.

true width

a. The width or thickness of a vein, stratum, etc., as measured perpendicular or normal to dip and strike. The true width is always the width of the vein, etc., at its narrowest point. CF: apparent width.

b. The true width of a vein in sampling may be found by w = h sin a , where h = horizontal width, w = true width, and a = angle of dip. In this formula, angle a is known from previous observations, and the horizontal width can be measured with a level. It is important that horizontal width is measured at right angles to strike.


Fibrous nodular lignite which when struck emits an odor like that of truffles. It occurs in large nodular masses inside a normal lignite of Cretaceous age in France.

truing-machine operator

One who grinds the surfaces of refractory blocks to reduce them to standard dimensions, using a truing machine.


Eng. A channel or passage partitioned off from a shaft or left behind the lining, usually running along one corner of the latter. Used for ventilation.

trumpet log

See: microlaterolog.

truncated spur

A spur that projected into a preglacial valley and was partially worn away or beveled by a moving glacier as it widened and straightened the valley. See also: faceted spur.


a. A long, narrow, inclined box in which fine ore is separated from impurities.

b. A launder for conveying slimes, etc. c. To separate slimes by means of a trunk for further treatment.

trunk conveyor

A high-capacity main road conveyor, usually a belt conveyor. It may extend from the main inby loading point to the shaft bottom or along levels or drifts to the surface. It varies from 42 to 60 in (1.07 to 1.52 m) wide and is powered by a motor of about 200 hp (149 kW). See also: conveyor; gathering conveyor.


a. A detonating cord line used to connect the downlines or other detonating cord lines in a blast pattern. Usually runs along each row of blastholes.

b. The line of detonating cord that is used to connect and initiate other lines of detonating cord, used on the ground surface to initiate downlines.

trunk pumping engine

A pump that commands the drainage of underground waters over a considerable area of mine workings, being a substitute for a number of smaller, independent pumps.

trunk roadway

The main development heading from the pit bottom, usually driven along the strike of the coal seam. Because it will carry heavy traffic and large volumes of air, a trunk roadway is at least 14 ft (4.3 m) wide and wide enough for two rail tracks. At intervals, crossheadings are excavated for opening out conveyor panels in the coal seam. Trunk roadways are usually driven in pairs for ventilation, storage space, and access.


a. Either of two opposite pivots, journals, or gudgeons, usually cylindrical and horizontal, projecting one from each side of a piece of ordnance, the cylinder of an oscillating engine, a molding flask, a converter, etc., and supported by bearings, to provide a means of swiveling or turning.

b. An oscillating bar that allows changes in angle between a unit fastened to its center, and another attached to both ends. c. A heavy horizontal hinge. Also called walking beam; walking bar.

trunnion axis

The horizontal axis about which the telescope of a theodolite can be rotated.

trunnion plate

A metal plate lining the bearings or recesses in which the trunnions rest.


A hexagonal mineral, (Ca,Mn) (sub 14) Si (sub 24) O (sub 58) (OH) (sub 8) .2H (sub 2) O ; in spherical aggregates of white scales; at Benkulen, Sumatra.


a. An assemblage of members, such as beams, bars, and rods, typically arranged in a triangle or combination of triangles to form a rigid framework, such as for supporting a load over a wide area that cannot be deformed by the application of exterior force without deformation of one or more of its members.

b. A framed structure built up entirely from tension and compression members, arranged in panels so as to be stable under load; used for supporting loads over long spans.

trussed beam

A beam of timber or other material that is stiffened so as to reduce deflection.


A green gem variety of garnet. Also spelled tsavorite.


See: cheremchite.


A monoclinic mineral, Ca (sub 2) (Mg,Fe) (sub 3) Al (sub 2) (Si (sub 6) Al (sub 2) )O (sub 22) (OH) (sub 2) ; amphibole group, having Mg/(Mg + Fe) = 0.5 to 1.0 ; forms a series with ferrotschermakite.


A synthetic manganese tourmaline or manganoan elbaite.


A monoclinic mineral, Pb (sub 2) Cu(PO (sub 4) )(SO (sub 4) )(OH) ; brackenbuschite group; in small, tabular, emerald-green crystals; at Tsumeb, Namibia.


a. A tram, wagon, corf, or corve.

b. A small rail-track vehicle for carrying coal or minerals, with a capacity ranging from 10 to 25 hundredweights (453.6 to 1,134 kg). Tub is the term used in most English mines; tram is used in South Wales; and hutch is used in Scotland. c. A box or bucket in which coal or ore is sent up a shaft. A keeve. d. To line, such as in a mine shaft, with tubbing; to keep back water by tubbing. See also: tubbing. e. A large circular base that provides the maximum practical bearing area, and on which is mounted the revolving frame or subbase of a walking dragline.


See: bord-and-pillar working.


A double-pointed pickax; a beele.

tubber man

A person who uses a tubber.


a. The watertight cast-iron lining of a circular shaft built up of segments that are fixed together with flanges. The flanges are internal and bolted in German tubbing; they are external in English tubbing, which gives a smooth inner face because the segments are wedged and not bolted. The space outside the tubbing is grouted to add strength and improve watertightness. See also: tub; suspended tubbing.

b. Eng. A lining of timber or metal for a shaft, as in a mine, esp. a watertight shaft lining consisting of a series of cast-iron cylinders bolted together and used to sink through water-bearing strata. c. A shaft lining of casks or cylindrical caissons of iron or wood. See also: plank tubbing; wooden tubbing.

tubbing wedge

A small wooden wedge hammered between the joints of tubbing plates.

tube-axial fan

An airfoil (propeller) or disk fan within a cylinder and including driving-mechanism supports either for belt drive or direct connection.

tube blower

A person who cleans boiler tubes.

tube clamp

a. A clamp or clip for gripping a tube or pipe; esp., a jawed tool used in hoisting and lowering well tubes in drilling.

b. A misnomer for casing clamp.

tube mill

A revolving cylinder, usually lined with silex, nearly half filled with glacial or water-worn flints, used for fine grinding of certain ores, preliminary to further treatment. The material to be ground, mixed with water, is fed through a trunnion at one end and passes out the opposite trunnion as a slime. This is an exceptionally long mill with a relatively small diameter. Syn: cylindrical mill.

tubercle texture

In mineral deposits, a texture in which gangue is replaced by automorphic minerals. CF: atoll texture.


A mineral exhibiting very irregular rounded surfaces, often giving rise to gnarled, rootlike shapes.

tub hooker

The person who hooks or unhooks the hoisting rope to or from the buckets.


a. The tube lining of boreholes; casing.

b. Hollow cast-iron segments placed in a shaft to dam water or sink through quicksand. Also spelled tubbing. c. See: ventilation tubing. d. A small-diameter removable pipe, suspended and immobilized in a well inside a large-diameter casing and opening at a producing zone, through which fluids are produced (brought to the surface). e. The act or process of placing tubing in a well. f. The act of lining a deep borehole by driving down iron tubes. See also: casing. g. A misnomer for casing. h. Small-diameter removable pipe through which oil and gas are produced from the well.

tubular screw conveyor

See: screw conveyor.


See: scarbroite.

tucking frame

A frame in timbering in which the poling boards are supported by walings at their upper and lower ends.

tucking space

The space between the blocks separating the cap in a heading set from the poling driven. This space provides for driving a second set of poling boards.

tue irons

Blacksmith's tongs.


A chemical sedimentary rock composed of calcium carbonate, formed by evaporation as a surficial, spongy, porous, semifriable incrustation around the mouth of a hot or cold spring or seep, or along a stream carrying calcium carbonate in solution, and exceptionally as a thick, bulbous, concretionary or compact deposit in a lake or along its shore. It may also be precipitated by algae or bacteria. The hard, dense variety is travertine. The term is rarely applied to a similar deposit consisting of silica. It is not to be confused with tuff. Etymol: Italian tufo. CF: sinter. Syn: calcareous tufa; calc-tufa; tophus; tuft; petrified moss.


Pertaining to or like tufa. Not to be confused with tuffaceous.


A general term for all consolidated pyroclastic rocks. Not to be confused with tufa. Adj: tuffaceous. CF: crystal tuff.


Said of sediments containing up to 50% tuff. CF: tufaceous.

tuff breccia

A pyroclastic rock consisting of more or less equal amounts of ash, lapilli, and larger fragments.


A tuff containing both pyroclastic and detrital material, but predominantly pyroclasts.

tuff lava

Applied to consolidated, lavalike tuff consisting primarily of lenses of black and gray obsidian lying in a tuffaceous matrix that displays a streaky, varicolored banding or eutaxitic structure. Rocks of this sort are generally considered to be the product of ash flows or ardentes. Syn: welded tuff.


Eng. Any porous or soft stone, such as the sandstone in the Alston district of Cumberland; tufa.

tuft stone

a. Eng. Tufa near Newport, Monmouthshire, and Dursley, Gloucestershire.

b. Eng. Toadstone, Derbyshire. See also: toadstone.


See: air hoist.

tugger hoist

An air hoist for mines.

tugger man

See: tugger operator.

tugger operator

In mining, a person who operates a small portable or semiportable hoist (tugger), powered by compressed air or electricity, to raise coal, ore, rock, or supplies in a shaft or stope or along an incline inside a mine. Also called tugger man.


A tetragonal mineral, Na (sub 4) AlBeSi (sub 4) O (sub 12) Cl ; in the Ilimaussaq massif, southwest Greenland. Formerly called beryllosodalite.


The working openings at the discharging end of a glass furnace.

Tukon hardness test

A method of determining the hardness of microconstituents by using the Knoop or Vicker's type of diamond indenter. See also: microhardness; Vickers hardness test.


To smooth, clean, or polish, as castings, by friction with each other or with a polishing material in a rotating box or barrel; to rattle.


Semiprecious and precious stones, cleaved carbon, or other diamonds, the sharp edges and corners of which have been rounded and blunted by tumbling action in a barrel-shaped vessel.


a. A projecting piece on a revolving shaft or rockshaft for actuating another piece. In dredges, both an upper and a lower tumbler support the bucket line.

b. Any piece of equipment that polishes gemstones by a tumbling action.

tumbler test

Test for determining relative friability of a particular size of sized coal.


An operation in which the work, usually castings or forgings, is rotated in a barrel with metal slugs or abrasives to remove sand, scale, or fins. It may be done dry or with an aqueous solution. Sometimes called rumbling or rattling.

tumbling barrel

A revolving barrel, cask, or box in which objects or materials (such as small metal parts, castings, plastics, leather, or clothing) undergo a process (such as finishing, polishing, coating, softening, or drying) by being whirled about and so brought into vigorous frictional contact. Also called rattler; rumble; scouring barrel.

tumbling box

A tumbling barrel for small objects.

tumbling mill

Any horizontally mounted cylindrical mill in which contents are tumbled when rotating. Name often used in connection with cleaning of objects.

tumbling shaft

The camshaft used in stamp mills.

tumbling stone

N. of Eng. Boulders or detached masses of rock.


The swelling of a volcanic edifice due to accumulation of magma in the reservoir. It may or may not be followed by an eruption. Syn: inflation.


A treeless, level or gently undulating plain characteristic of arctic and subarctic regions. It usually has a marshy surface, which supports a growth of mosses, lichens, and numerous low shrubs and is underlain by a dark, mucky soil and permafrost.

tundra placer

See: gravel plain placer.


A monoclinic mineral, SrB (sub 6) O (sub 9) (OH) (sub 2) .3H (sub 2) O ; subvitreous to pearly; colorless; forms compact fine-grained secondary nodules; also prismatic and tabular crystals; at Kramer and in the Furnace Creek area of Death Valley, CA.

tune work

Labor paid for by the day or the hour, in contrast to piecework.


A mineral containing the radical (WO (sub 4) ) (super 2-) , in which the hexavalent tungsten ion and its four oxygens form a flattened square rather than a tetrahedron, e.g., the wolframite series, (Fe,Mn)WO (sub 4). Tungsten and molybdenite may substitute for each other.


A hard, brittle, white or gray metallic element. Symbol, W. Also known as wolfram. Found combined in certain minerals such as wolframite, (Fe,Mn)WO (sub 4) ; scheelite, CaWO (sub 4) ; huebnerite, MnWO (sub 4) ; and ferberite, FeWO (sub 4) . Tungsten and its alloys are used extensively for filaments for electric lamps, electron and television tubes, X-ray targets, and numerous space missile and high-temperature applications. See also: wolframite. Syn: wolfram.

tungsten alloy

An alloy used in drill-bit-crown matrices and in making bit and reaming-shell inserts by powder methods in which the principal constituent is tungsten, generally in the form of carbide. Tungsten carbide powder usually is mixed with a powdered cobalt or other metal to bind it together in a cohesive mass.

tungsten carbide

A mixture consisting of 85% to 95% tungsten carbide and 5% to 15% cobalt; sp gr, 12 to 16; Mohs hardness, about 9.0; it is not affected by severe high industrial temperatures. Used for machine tools and for abrasives for machining and grinding metals, rocks, molded products, porcelain, and glass.

tungsten carbide bit

A drilling bit tipped with tungsten carbide. A 9% cobalt carbide generally gives the best results, and comparisons are usually referred to bits of this standard. Tests with tungsten carbide bits indicate that efficient drilling is possible only up to a hardness of about 55 Shore; beyond this, wear increases rapidly until, at 62 Shore, the cost becomes prohibitive. Several factors affect the cutting life of the bits, including the grade of carbide used, the rake angle of the cutters, the length of cutting edges, and support of cutters. See also: steel bit; coal-cutter pick; Shore hardness test; sintered carbide-tipped pick.

tungsten carbide insert

a. A small plate or slug of tungsten carbide alloy mounted in the crown or shank of a bit or in grooves on the outside surface of a reaming shell to provide wear-resistant or rock-cutting surfaces or edges. The term is sometimes incorrectly applied to diamond-set plates of tungsten carbide alloy inset as reaming surfaces in reaming shells.

b. In mining, a slug composed of tungsten carbide alloy shaped and mounted in the bit face so that the slug acts as the cutting edge of the bit. c. Hemispherical-ended cylinders of sintered carbide are inserted in place of the usual teeth to give 10 to 15 times the total footage and 2 to 3 times the cutting rate. However, hard rocks are drilled more economically by diamond boring.

tungsten direct-from-ore process

An electrowinning method developed by the U.S. Bureau of Mines for producing high-quality tungsten powder directly from ore. A strong electric current separates the metal from the ore, which has been placed in solution, and deposits it as a pure powder on an electrode. Electrowon tungsten compares favorably with hydrogen-reduced tungsten.


A trigonal or hexagonal mineral, WS (sub 2) ; forms dark, lead-gray, minute, foliated or earthy scales; at the Emma Mine, Utah.

tungstic ocher

See: ferritungstite; tungstite. Also called wolfram ocher.


An orthorhombic mineral, WO (sub 2) (OH) (sub 2) ; yellow to green; in oxidized zone of tungsten deposits. Syn: tungstic ocher; wolframine.


A Welsh term for a hoisting bucket; a bowk; a kibble.


a. A horizontal or inclined stone drivage for development or to connect mine workings, seams, or shafts. It may be open to the surface at one end and used for drainage, ventilation, or haulage or as a personnel egress (walking or riding) from the mine workings. See also: tunneling.

b. See: crut. c. A leaden tube used in making sulfuric acid to connect adjoining chambers in a series. d. A long, narrow subterranean passageway. e. A horizontal or nearly horizontal underground passage that is open at both ends. The term is loosely applied in many cases to an adit. An adit, if continued through a hill, would be a tunnel. Any level or drift in a mine open at one end, or which may serve for an adit. Often used as a syn. for adit; drift; gallery. See also: adit. f. To penetrate with or as if with a tunnel; to make a passage through or under; to make or use a tunnel; to undermine.

tunnel blast

a. A blast effected by the detonation of great quantities of explosive, loaded in small tunnels driven into the face at the level of the quarry floor or at the level of the terrain at the foot of the slope of the deposit. This blasting method is called tunneling.

b. See: heading blast.

tunnel blasting

A method of heavy blasting in which a heading is driven into the rock and afterwards filled with explosives in large quantities. This is similar to a borehole on a large scale, except that the heading is usually divided into two parts on the same level at right angles to the first heading. This forms a T, the ends of which are filled with explosives and the intermediate parts of which are filled with inert material like an ordinary borehole. Similar to gopher hole blasting. See also: gopher hole blasting.

tunnel borer

Any boring machine for making a tunnel; often a ram armed with cutting faces operated by compressed air.

tunnel carriage

A rapid tunneling procedure, consisting of a combined drill carriage and manifold for water and air so that immediately when the carriage is at the face, drilling may commence with no lost time for connecting up, waiting for drill steels, etc. The air is supplied at pressures of 95 to 100 psi (655 to 690 kPa).

tunnel claim

When a lode or vein is discovered in a tunnel, the tunnel owner is called upon to locate the area containing the vein or lode on the surface and thus create a mining claim.

tunnel column

A heavy bar used for mounting machine drills in large drifts or tunnels, and usually holding two machines.

tunnel excavation

Excavation carried out completely underground and limited in width and height.

tunnel face

The working face in an excavation or tunnel or other working place from which driving is carried out.


The operation of excavating, driving, and lining tunnels.

tunnel kiln

A long tunnel-shaped furnace through which the charge is generally moved on cars, passing progressively through zones in which the temperature is maintained for preheating, firing, and cooling.

tunnel-kiln operator

One who controls the operation of a tunnel kiln in which bricks are fired, and a preheating chamber in which bricks are heated prior to firing and after drying.

tunnel lining

a. The timber, brick, concrete, or steel supports erected in a tunnel to maintain dimensions and safe working conditions. See also: steel tunnel support; lining.

b. See: ring; tunnel support.


In anthracite coal mining, one who drives a tunnel in rock from one coal seam to another or through a fault (the movement of the earth having separated a once continuous seam into two sections).

tunnel miner

A miner experienced in the use and handling of rock drills and shovel loaders, and in tunnel-blasting methods. Such a miner is wholly employed on tunneling and is usually paid a fixed rate per shift with perhaps a bonus payment for high rates of tunnel advance.

tunnel right

A right to enter upon and occupy a specific piece of ground for the purpose of carrying out work in a tunnel and extracting waste rock or earth necessary to complete the tunnel, and making such use after completion as may be necessary to work the mining ground or lode owned by the party running the tunnel. By implication, the grant of such a right carries with it every incident and appurtenant thereto, including the right to dump the waste rock at the mouth of the tunnel on the land owned by the grantor at the time of the conveyance of the tunnel right, such right or easement being necessary for the full and free enjoyment of the tunnel right.

tunnel set

Timbers of sufficient strength to support the roof of the tunnel. They are sometimes set upon sills and usually capped with short crosspieces.

tunnel shaft

A shaft sunk, such as in a hill, to meet a horizontal tunnel. Also called tunnel pit.

tunnel site

a. An area for a tunnel. The locator of a tunnel site is given the right to all veins cut by the tunnel within 3,000 ft (915 m) of its portal, and 1,500 ft (457 m) on the strike of each blind vein cut; this length may be all on one side of the tunnel or divided as desired. The veins must be blind lodes not previously known to exist.

b. There is no distinction between a tunnel claim under which a tunnel is run for the development of veins or lodes already located, and one where a tunnel is projected for blind veins or lodes.

tunnel support

See: steel tunnel support; tunnel lining.

tunnel system

A method of mining in which tunnels or drifts are extended at regular intervals from the floor of the pit into the orebody. The extension of the drift beyond the working face is made great enough to facilitate the handling of several cars at a time. The ore is mined above the drift level, and the cars are loaded by lifting short boards that span an opening, through the lagging on and above the centerline of the drift. The method avoids the construction of raises and chutes and facilitates the filling of the cars.


The ram or monkey, or falling weight, of a piledriver, drophammer, etc.; specif., the heavy head of a steam hammer in which the upper pallet is secured.


An orthorhombic(?) mineral, Cu (sub 5) (VO (sub 4) ) (sub 2) (OH) (sub 4) (?) ; weakly radioactive; green; forms reniform crusts and spherical concretions having a radial fibrous structure with other vanadium and uranium minerals; in cavities in limestone; at Tyuya Muyun, Fergana, Turkistan.


Stirred up or disturbed, such as by sediment; not clear or translucent, being opaque with suspended matter, such as of a sediment-laden stream flowing into a lake; cloudy or muddy in physical appearance, such as of a feldspar containing minute inclusions.


An instrument for measuring or comparing the turbidity of liquids in terms of the reduction in intensity of a light beam passing through the medium. See also: transmissometer.


Measurement of the amount of suspended or slow-settling matter in a liquid; the measurement of the decrease in intensity of a light beam passed through a medium. CF: nephelometry.


A sediment or rock deposited from, or inferred to have been deposited from, a turbidity current. It is characterized by graded bedding, moderate sorting, and well-developed primary structures.


a. The state, condition, or quality of opaqueness or reduced clarity of a fluid, due to the presence of suspended matter.

b. A measure of the ability of suspended material to disturb or diminish the penetration of light through a fluid.

turbidity current

A density current in water, air, or other fluid, caused by different amounts of matter in suspension, such as a dry-snow avalanche or a descending cloud of volcanic dust; specif. a bottom-flowing current laden with suspended sediment, moving swiftly (under the influence of gravity) down a subaqueous slope and spreading horizontally on the floor of the body of water, having been set and/or maintained in motion by locally churned- or stirred-up sediment that gives the water a density greater than that of the surrounding or overlying clear water. Such currents are known to occur in lakes, and are believed to have produced the submarine canyons notching the continental slope. They appear to originate in various ways, such as by storm waves, tsunamis, earthquake-induced sliding, tectonic movement, oversupply of sediment, and heavily charged rivers in spate with densities exceeding that of sea-water. The term is applied to a current due to turbidity, not to one showing that property. Syn: suspension current.

turbidity size analysis

A kind of particle-size analysis based upon the amount of material in turbid suspension, the turbidity decreasing as the particles settle.

turbine pump

A pump with a shrouded impeller and receiving the water at its center. A diffusion ring containing vanes surrounds the impeller and directs the impeller discharge into a circular casing, which delivers into the eye of the next impeller in series. The diffusion ring converts the high-velocity discharge of the impeller into pressure head. The turbine pump is widely used in mines. See also: diffuser chamber.

turboaxial fan

An axial flow fan with a turbine rotor-type impeller.


The type of machine commonly installed at a colliery today where a large volume of compressed air is required. A single unit can deliver 10,000 ft (super 3) /min (283 m (super 3) /min) or more of free air, and the floor space occupied is a minimum for these capacities. It is also ideally suited for direct drive by a steam turbine, and this combination is commonly found at collieries. The compressor consists essentially of a number of impellers keyed to a shaft and running in a fixed casing with specially shaped passages. Each impeller is in the form of a hollow wheel, the two sides being united by curved vanes. See also: air-conditioning process.


In rotary drilling, a drill bit that is directly rotated by a turbine attached to the drill pipe at the bottom of the hole and driven by drilling mud pumped under high pressure. It was developed in the former U.S.S.R. for drilling deep oil wells.


A system of drilling in which the bit is directly driven by a turbine at the bottom of the hole.


See: turbulent flow.

turbulent flow

a. Water flow in which the flow lines are confused and heterogeneously mixed. It is typical of flow in surface-water bodies. CF: laminar flow. Syn: tortuous flow; turbulence.

b. Fluid motion in which random motions of parts of the fluid are superimposed upon a simple pattern of flow. All or nearly all fluid flow displays some degree of turbulence. Opposite of streamline flow. c. A fluid flow in which there is an unsteady motion of the particles, the motion at a fixed point being inconstant. Turbulent flow occurs at a speed above the critical velocity of Reynolds. Also called tortuous flow; sinuous flow; eddy flow. d. When air flows over roughnesses on the sides of the airway or passes obstructions at over a certain velocity, eddies are set up in the air and its flow becomes turbulent. Opposite of laminar flow. e. When the fluid particles are moving in directions other than in a straight line parallel to the axis of the pipe or duct.

turbulent resistance

Resistance that causes vortices and eddies to form behind a moving particle because of the rapid displacement of the liquid when the body moves through it. CF: viscous resistance.


a. Same as peat. There are several varieties, as white, brown, black, stone, gas, or candle turf.

b. Sod, the upper strata of topsoil filled with the roots of grass and other small plants.


An iron ore and sandstone cement consisting of hematite with adsorbed water. It is fibrous and red in mass with an orange tint where powdered. Also spelled turjite. Syn: hydrohematite.

Turkey slate

A whetstone or honestone. See also: Turkey stone.

Turkey stone

A very fine-grained siliceous rock, containing up to 25% calcite, quarried in central Turkey and used as a whetstone; novaculite. Syn: Turkey slate. See: novaculite; turquoise.


A turquoise.

turmeric paper

Paper impregnated with an extract of turmeric. Used as a test for alkaline substances, which turn it from yellow to reddish-brown, and for boric acid, which turns it red-brown.


a. A curve into a pillar.

b. The time or period during which coal, etc., is raised from a mine. Also called run; shift. c. To open rooms, headings, or chutes off from an entry or gangway. d. The number of cars allowed each miner. Good turn means many cars for each miner. e. To draw or wind coal up a shaft or up an inclined plane to the surface. f. Curved tramrails, often made of cast iron, laid round a corner or turn. g. To set undried bricks on edge to facilitate drying.

turn angles

To measure the angle between directions with a surveying instrument.

turn bat

A wooden stick used in turning the tongs that hold a bloom under the hammer.

turn bolt

A bolt turned in a lathe to a close tolerance and used in steel-to-steel connections.

turned vertical shaft

A shaft sunk vertically in the hanging wall block until it intersects a reef, after which it is sunk down at an angle in the footwall parallel to the reef. This unusual practice is sometimes adopted on the Rand because it enables the mine to become productive at an earlier stage. See also: incline shaft.


A yellowish-brown variety of monazite.


a. A point where workings turn from a crosscut to a level along the lode.

b. The first cutting on a lode after it is cut in a crosscut. Syn: house.

turning effect

See: moment of force.

turning over and packing shift

On mechanized longwall faces, the shift during which face conveyors are moved over, and the operations of ripping, packing, and drawing supports from the wastes are performed.

turning point

a. A surveying point on which a level rod is held, after a foresight has been made on it, and before the differential-leveling instrument is moved to another station so that a backsight may be made on it to determine the height of instrument after the resetting; a point of intersection between survey lines, such as the intervening point between two bench marks upon which rod readings are taken. It is established for the purpose of allowing the leveling instrument to be moved forward (alternately leapfrogging with the rod) along the line of survey without a break in the series of measured differences of elevation. Abbrev: TP.

b. A physical object representing a turning point, such as a steel pin or stake driven into the ground.

turning vane

Curved strips placed in a sharp bend or elbow in rectangular duct to direct the air around the bend in a streamlined flow.

turn keeper

See: motor boss.


a. The branching off of one rail track from another.

b. A contrivance for passing from one track to another. c. A siding or bypass in an underground haulageway. d. A switch on a mine railroad.


a. The distance the conveyor is advanced during each cycle of operations; i.e., approx. the depth of machine cut. See also: conventional machine mining.

b. A device used to rotate an object through approx. 180 degrees so that its carrying surface is changed to the opposite side. c. See: move-up.

turn pulley

A sheave fixed at the inside end of an endless or tail-rope hauling plane, around which the rope returns. See also: tail sheave.


A term used with any device used to change the direction of a shaker conveyor trough line; e.g., curved trough turn, adjustable angle turn, right angle turn, etc. The angle turn corresponds to the bell crank drive in principle of operation.


See: flat sheet.


a. A triclinic mineral, 1[CuAl (sub 6) (OH) (sub 8) (PO (sub 4) ) (sub 4) .4H (sub 2) O] with Fe replacing Al toward chalcosiderite; forms waxy blue-green reniform masses having a botryoidal surface, rarely with minute crystals; occurs in arid regions where surface water acted on aluminous rock; may be a gemstone. Also spelled turquois. Syn: Turkey stone; calaite.

b. The mineral group aheylite, chalcosiderite, coeruleolactite, faustite, planerite, and turquoise.

turret coal cutter

A coal cutter in which the horizontal jib can be adjusted vertically to cut at different levels in the seam, for example, an overcut. The center of gravity of such a machine makes it top heavy and less stable than the ordinary undercutter. See also: overcutting machine; universal coal cutter.

turret jib

A vertical rotating jib fitted with cutter picks and driven from the end sprocket of the bottom jib of a coal cutter. The turret jib is satisfactory in seams where the coal parts readily from the roof and is not too hard. See also: mushroom jib; curved jib.

turtle back

A name for chlorastrolite (pumpellyite), esp. the green variety with patches of color; also, turquoise matrix or variscite matrix.

turtle stone

See: septarium.


Large, nodular concretions found in certain clays and marls. In form, they have a rough resemblance to turtles, and this appearance is increased by their being divided into angular compartments by cracks filled with spar, reminding one of the plates on the shell of a turtle.

Tuscarora quartzite

An important source of raw material for silica refractories. A typical analysis is 97.8% SiO (sub 2) , 0.9% Al (sub 2) O (sub 3) , 0.7% Fe (sub 2) O (sub 3) , and 0.4% alkalies.


A former name for calciocopiapite.


a. A white alloy, resembling German silver, used in making tableware, etc., with varying proportions of copper, zinc, nickel, and sometimes a little lead or iron.

b. Zinc or spelter, esp. that from China and the East Indies.


A foam-producing agent used in fire extinguishers.


Sometimes used for piecework or contract work.


A pyroxene mineral, (Na,Al,Ca,Mg)Si (sub 2) O (sub 6) ; midway in composition between diopside and jadeite; pea-green; massive; at Tuxtla, Mexico. Formerly called diopside-jadeite. Also spelled tuxlite.


A tube or opening in a metallurgical furnace through which air is blown as part of the extraction or refining process. In a blast furnace, the tuyeres are water-cooled metal tubes which pass through the refractory lining of the bosh (tube).

tuyere arch

An arch in a blast furnace to admit a tuyere. See also: tuyere.

tuyere brick

A refractory shape containing one or more holes through which air and other gases are introduced into a furnace.


A counterweighted furnace door, opening vertically. Also spelled tuille.


a. See: divining rod.

b. Thin strip of plastic fire clay used in ceramic modeling, esp. in imitation basketwork.

twill cloth

Weave used in screens and filters, in which two or more warp threads interweave one wood thread.

twin axis

The crystal axis about which one individual of a twin crystal may be rotated (usually 180 degrees ) to bring it into coincidence with the other individual. It cannot be coincident with the axes of twofold, fourfold, or sixfold symmetry. Syn: twinning axis.

twin colors

See: dichroic colors.

twin-core shot-firing cable

See: shot-firing cable.

twin crystal

A composite of two or more crystal individuals having a definite crystallographic relationship to each other. The orientation of one individual may be the mirror image of the other across a twin plane, or an orientation that can be derived by rotating the twin portions about a twin axis, or some other rational twin law. Twinned individuals in a twin crystal commonly show reentrant angles between crystal faces or on cleavage planes. A twin crystal may exhibit symmetry higher than that of its crystal individuals.

twin crystals

Crystals in which one or more parts, regularly arranged, are in reverse position with reference to the other part or parts. They often appear externally to consist of two or more crystals symmetrically united, and sometimes have the form of a cross or star. They also exhibit the composition in the reversed arrangement of part of the faces, in the striae of the surface, and in re-entering angles; in certain cases, the compound structure can only be surely detected by an examination in polarized light.

twin entry

A pair of parallel entries, one of which is an intake air course and the other a return air course. Rooms can be worked from both entries. Often called double entry.

twin laminae

The laminae or thin plates in repeated or polysynthetic twins. CF: polysynthetic twinning; repeated twinning.

twin law

A statement or statements of the symmetrical relationships between the members of a twin crystal, e.g., the twin plane or the twin axis that resolves one crystal individual into congruity with another in a twin crystal. The twin law cannot be an element of symmetry of the point group of the twin parts, although it may be an element in a point group with higher symmetry in the same crystal system.

twinning axis

See: twin axis.

twinning law

The special and characteristic method according to which twin crystals of any mineral are formed.

twinning plane

In a twin crystal, a plane normal to the twinning axis.


A type of instrument used to detect and mark twinning and determine the sense of orientation in etched sections.


An instrument employing a directed beam of light used to examine etched wafers for twinning.

twin packer

A packer designed so that a borehole can be sealed simultaneously at two separated points.

twin plane

In a twin crystal, a plane through which one twin individual forms a mirror image of the other, or the plane at right angles to the axis about which one individual is rotated with respect to the other. The twin plane is commonly the composition plane across which the individuals are joined. With rare exceptions, a twin plane is a possible crystal face for the crystal individuals.

twist conveyor

An L-shaped conveyor in which the carrying surface and guard gradually exchange their functional duties.

twist drill

A drill made by twisting a length of steel of rectangular or oval section into a spiral form, hence the term twist drill. Many hand-operated coal drills are of this type, and the rotation of the drill spiral removes the cuttings from the hole. See also: auger; coal auger.

twisted-loop splice

Splice made by holding the bared wires side by side. Half of their length is bent back to form a loop at the end. The loop is then twisted around the main shank of wire.

twister operator

In the asbestos products industry, one who twists together two or more strands of wire and asbestos yarn for use in weaving asbestos products, such as brake linings.

twisting force

A force, such as the force on the shaft of a rotating motor.


The breaking off of a member of the drill string, caused by excessive torsional stress.

two-circle goniometer

A device permitting rotation of a small crystal about two orthogonal axes for optical observation. CF: goniometer.

two-component explosives

Consist of two or more unmixed, commercially manufactured, prepackaged chemicals, including oxidizing chemicals, flammable liquids, or solids that are not independently classified as explosives. When combined, however, the mixture is classified as an explosive and is stored, transported, and handled as an explosive.

two-cone bit

See: roller rock bit.

two-fan auxiliary ventilation

An arrangement, using two auxiliary fans, for ventilating a mine tunnel or hard heading. It consists of an exhausting fan with rigid ducting to within about 100 ft (30 m) of the face, and a forcing fan using a flexible duct discharging air about 20 ft (6 m) from the face. The ducts of the two units overlap by at least 30 ft (9 m) to minimize the recirculation of air. The air delivered by the forcing fan does not exceed about one-third of that removed by the exhaust fan. See also: overlap auxiliary ventilation; auxiliary ventilation; recirculation of air; reversible auxiliary ventilation.


A symmetry axis requiring two repetitions to complete 360 degrees and return to identity. Syn: diad.

two-high mill

Contains two horizontal rolls, one above the other. In some two-high mills the direction of rolling can be reversed, and these are known as reversing mills; i.e., when a piece has passed through the rolls, the rolls are stopped and then rotated in the opposite direction, thus imposing another pass on the steel, the operation being repeated until the desired reduction is attained. Between passes, adjustment is made to the height of the top roll, and/or the piece is moved sideways by means of manipulators, to be in line with other grooves in the rolls.

two-hinged arch

A rigid frame hinged at both supports. It may have an arched or rectangular form.

two intakes

The provision of two intake airways, generally side by side, to a ventilating area of a mine.

two-jaw chuck

A chuck equipped with two movable clamping or holding devices by means of which the motion of the chuck is imparted to the drill rods.

two-leg sling

A sling having two chains or ropes which hang from a thimble. See also: single sling.

two-liquid differential manometer

Consists of two concentric glass tubes, each expanded into a large bulb at the upper end. The lower end of the outer tube is sealed, and the inner tube reaches nearly to the bottom of the outer tube. Two liquids are used, and the movement of the interface between the two liquids down the central tube is used as an index against which the change in pressure is measured. See also: manometer.

two-mica granite

A granite containing both dark mica (biotite) and light mica (muscovite). This rock was called true granite by Rosenbusch and binary granite by Keyes. CF: aplogranite.

two-part line

A single strand of rope or cable doubled back around a sheave so that two parts of it pull a load together.

two-piece set

A set of timbers consisting of a cap and a single post. If the ground is loose and must be supported over the side or back, lagging, commonly of 2-in (5.1-cm) boards, is used. These boards extend from the center line of the post or cap to the middle of the next post or cap. If they are placed touching each other, such an arrangement is called tight lagging; if a few inches apart (which depends on the nature of the ground to be held back), it is called open lagging. See also: timber set.

two-plane idler

A troughing idler in which the troughing roll shafts are in a vertical plane separate from but parallel to a vertical plane through the shaft of the center roll or rolls.

two-process washer

A method of cleaning raw coal in which the material from 8 to 1/16 in (203 to 1.6 mm) in size is treated in heavy-medium washers, and the fines below 1/16 in are treated by froth flotation.

two-speed differential

A differential having a high-flow gearshift between the drive shaft and the ring gear.

two-stage compression

Air compression carried out in two stages as is usual for pressures exceeding 60 psi (414 kPa) or for outputs greater than 100 hp (74.6 kW). See also: intercooler.

two-stage hoisting

Deep-shaft hoisting with two winders, one at the surface and the other at middepth in the shaft. The surface engine winds minerals from the middepth pocket, and the other winds from the pit bottom to the middepth point. The arrangement is often adopted in turned vertical shafts. See also: tandem hoisting.

two-step control system

In flotation, a system in which the manipulated variable alternates between two predetermined values.

two-stroke cycle

A working cycle of a piston in an internal combustion engine consisting of two strokes, in which the piston during the first stroke compresses the fuel mixture on one side while receiving the expansive thrust of previously compressed gases on the other side, and during the second draws in a fresh charge on one side while expelling burnt gases on the other.

two-way ram

A hydraulic cylinder in which fluid can be supplied to either end, so the piston can be moved by power in two directions. Syn: double-acting ram.


An isometric mineral, Na (sub 6) Mg (sub 2) (CO (sub 3) ) (sub 4) (SO (sub 4) ) , having iron replacing magnesium toward ferrotychite; isomorphous with northupite, Na (sub 6) Mg (sub 2) (CO (sub 3) ) (sub 4) Cl (sub 2) , with which it occurs; forms small white octahedra; at Borax Lake, San Bernadino County, CA.

tying across and behind

Systematic exploration by a mine rescue team of all intersecting and adjacent passageways so that the team is never forward (toward the working face) of an accessible, unexplored area.

Tyler sieve

See: sieve.

Tyler Standard series

The series of carefully woven, square-mesh wire screens most commonly used in the United States in screening ores.


Eng. A horizontal roof timber in a coal mine; a cap or lid.

tymp stone

A large clay plug filling an open space in the front jackets of a smelting furnace, through which the taphole passes.


See: tyndallometer.

Tyndall effect

The scattering or reflection of a strong beam of light by suspended colloids; no such scattering or reflection comes from true solutions.


An instrument that measures the intensity of the light scattered at an angle from the incident beam by a dust cloud. It correlates well with the concentration determined by a thermal precipitator and surface area calculated from such a count. It needs to be calibrated for each type of dust against the thermal precipitator. Syn: tyndalloscope. See also: dust sampling.


See: tyndallometer.


a. See: rock type.

b. A coal classification based on the constituent plant materials. CF: rank; grade. c. Those differences in coals that are due to variations in the kind of plant material of which the coal is composed, whereby such varieties as common banded coal, cannel coal, algal coal, and splint coal are produced. d. A kind, particularly in petrology (rock type); either general (for example, basalt is a rock type) or particular (for example, a particular basalt from a particular locality is a unique type specified by a description).

type-D drift indicator

A single-shot borehole-surveying instrument utilizing photographic paper on which is recorded the compass bearing and inclination of the course of a borehole. The type-D instrument, when mounted in a special thin-walled protective container, is small enough to be used in an AX-size hole.

type-M drift indicator

A single-shot borehole-surveying instrument that records the compass bearing and inclination of the course of a borehole through the action of a strong beam of light directed through the plumb bob onto a light-sensitive paper disk. It is similar to, but larger than, a type-D drift indicator.

type of coal

a. The concept type provides a means for classifying standard varieties of coal microscopically on the basis of simple proportions of anthraxylon or anthraxylon and opaque attritus, including their subdivision into banded and non-banded coals.

b. A type of coal is a variety initially determined by the nature of the ingredient matter, the conditions of deposition, and the extent of operation of the first or biochemical process of coal making.

type section

The originally described sequence of strata that constitute a stratigraphic unit. It serves as an objective standard with which spatially separated parts of the unit may be compared, and it is preferably in an area where the unit shows maximum thickness and is completely exposed (or at least shows top and bottom).

type specimen

A specimen or individual designated as type of a species or lesser group and serving as the final criterion of the characteristics of that group.

type-W drift indicator

A mechanical single-shot borehole-surveying instrument for use where exceptionally high temperatures are encountered in a hole. It records the compass bearing and inclination of a borehole by making a dot on a special paper by means of a plumb bob, incorporating a depressible stylus.

typhonic rocks

Rocks that have come from the depths of the Earth; i.e., plutonic and eruptive rocks.

typomorphic mineral

A mineral that is typically developed in only a narrow range of temperature and pressure. CF: index mineral.


a. A variety of fergusonite found near Arendal, Norway.

b. See: sipylite.

tyre valve

Adjustable annular ring, made of plastic, used to control the aperture area at the apex of a hydrocyclone.


An orthorhombic mineral, Ca (sub 2) Cu (sub 9) (AsO (sub 4) ) (sub 4) (OH) (sub 10) .10H (sub 2) O ; forms green crystal aggregates having foliated micaceous structure. Formerly called trichalcite.


An orthorhombic mineral, Ca(UO (sub 2) ) (sub 2) (VO (sub 4) ) (sub 2) .8H (sub 2) O ; soft; waxy; yellow; fluoresces yellow-green; in secondary encrustations in limestones, sandstones, or concentrated by organic matter; associated with malachite, ferghanite, turanite, barite, calcite, carnotite, and vanadium minerals; widely distributed in the Colorado Plateau area; source of uranium and vanadium. Formerly called calciocarnotite.