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

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a. Granulated material obtained by pouring melted material into water.

b. In the roof of a coal seam, a funnel-shaped downward intrusion of sedimentary rock, usually sandstone. See also: stone intrusion. c. The vertical displacement in a downthrow fault; the amount by which the seam is lower on the other side of the fault. d. In an air lift, the distance the water level sinks below the static head during pumping. e. The small downward descent of the upper section of a drill rod, casing, or pipe into a lower like section when the threads of the box- and pin-threaded parts match, so that upper and lower sections may be screwed together without cross-threading. f. The sudden descent of a bit that occurs when a bit encounters a cavity or cuts through a hard rock and enters a very soft rock. g. To lower drill-string equipment into a borehole. h. To lower the cage to receive or discharge the car when a cage of more than one deck is used. i. To allow the upper lift of a seam of coal to fall or drop down. j. To lose equipment in a borehole.

drop ball

A method of breaking oversize stones left after quarry blasting. The balls weigh from 30 hundredweight (1,360 kg) to 2 st (1.8 t) (many use old cones from gyratory breakers) and are dropped from a crane on to the oversize stone. The drop height varies from about 20 to 33 ft (6.1 to 10.1 m). The method is economical and avoids secondary blasting.

drop-bottom cage

A cage so designed that the middle section of the floor drops a few inches when the cage is lifted from the keps. The mine car is thus kept stationary and secure.

drop-bottom car

A mine car so constructed that all the haulage motor has to do is to pull the loaded trip across the dump. A trigger trips the flaps in the bottom of the car, allowing the coal to drop out, and a second one closes the flaps as the car leaves the dump. See also: mine car.

drop box

Placed at intervals along tailings line to compensate for slope in excess of that required to keep the pulp moving gently through its launders or pipes.

drop cut

The initial cut made in the floor of an open pit or quarry for the purpose of developing a bench at a level below the floor.

drop doors

Hinged doors at the bottom of a cupola furnace, which drop down to allow the furnace to be cleaned.


a. A forging hammer that depends on gravity for its force.

b. A pile driving hammer that is lifted by a cable and obtains striking power by falling freely.

drop log

A timber that in an emergency can be dropped by a remote control across a mine track at the top or bottom of an incline to derail cars.

drop on

Portable rail crossing used to transfer wagons from one track to another.

dropped core

Pieces of core not picked up or those pieces that slip out of the core barrel as the barrel is withdrawn from the borehole.


a. A branch vein pointing downwards. See also: leader.

b. A spar dropping into the lode. c. See: feeder. d. A branch leaving a vein on the footwall side. e. See: car runner; car dropper.

dropping pillars and top coal

Aust. The second working, consisting of drawing the pillars, and in thick seams breaking down the upper portion of the seam that was left temporarily in position.

dropping stones

See: stalagmite.

drop pit

A shaft in a mine, in which coal is lowered by a brake wheel.


Drops of 12 in (30.5 cm) or more in a line of sluices that are formed by allowing the discharge end of one box to rest on the head of the succeeding sluice, instead of telescoping into it. This method ensures a drop of 12 in or more (depending on the depth of the sluice box) at the end of each sluice, which usually is sufficient to disintegrate fairly stiff clay.

drop shaft

A monkey shaft down which earth and other matter are lowered by means of a drop (that is, a kind of pulley with brake attached); the empty bucket is brought up as the full one is lowered. See also: cofferdam.

drop-shaft method

This sinking system consists in the use of a cutting shoe on the bottom of a shaft lining that is being continually augmented as the shoe descends, the material inside the lining being excavated.

drop sheet

N. of Eng. A door, made of canvas, by which the ventilating current is regulated and directed through the workings. See also: curtain.

drop staple

Eng. An interior shaft, connecting an upper and lower seam, through which coal is raised or lowered.


a. An oversized clast in laminated sediment that depresses the underlying laminae and may be covered by "draped" laminae. Most dropstones originate through "ice-rafting"; other sources are floating tree roots and kelp holdfasts.

b. A stalagmatitic variety of calcite. CF: dripstone.

drop sulfur

Granulated material obtained by pouring the melted material into water.

drop warwicks

Steel joists hinged to a substantial cross joist in the roof that are held up by a stirrup during normal running. If a tram runs away down the incline, the stirrup is disengaged by means of a wire operated from the top of the incline; one end of the hinged joist falls into the rail track and arrests the runaway.

drop ways

Openings connecting parallel passages that lie at different levels.

drop weights

A method of breaking oversize stones after primary blasting at a quarry. See also: drop ball.


a. The scum that forms on the surface of molten metals largely because of oxidation, but sometimes because of the rising of impurities to the surface, and which contains metal and metal oxides.

b. Small coal that is inferior or worthless and often mixed with dirt. c. Refuse or impurity formed in melted metal. A zinc-iron alloy forming in a bath of molten zinc while galvanizing iron.

dross bing

Pile of refuse from a washer.


Flooded; said of mines underwater.

drowned level

a. A level that is underwater. See also: blind level.

b. Part of a drainage drift that, being below both discharge and entry levels, is constantly full of water. Also called inverted siphon.

drowned waste

Old workings full of water.

Drucker-Prager criterion

A soil and rock failure criterion, which accounts for the general effect of all three principle stresses by using the invariant of the stress tensor. Use is limited to numerical formulations, such as finite element analysis.

druid stone

One of the large sandstone blocks formerly scattered on the English chalk downs and used in Stonehenge and other Druid temples and circles. Syn: sarsen stone.


a. The large cylinder or cone on which the rope is coiled when hoisting a load up a shaft.

b. A metal cask, for shipment of material, having a liquid capacity of 55 gal (208 L). See also: barrel. c. In a conical mill, the cylindrical central section. d. A general term for a roller around which a belt conveyor is lapped. It may be a driving, jib, loop, tension, or holding-down drum. e. The spoollike part of a hoisting mechanism on which the cable or wire line is wound. f. A cylindrical or polygonal rim type of wheel around which cable, chain, belt, or other linkage may be wrapped. A drum may be driven or driving. The face may be smooth, grooved, fluted, or flanged.

drum counterweight rope

Balance rope direct from drum drive.

drum curb

See: curb.

drum feeder

See: roll feeder.

drum filter

Cylindrical drum, which rotates slowly through trough-shaped bath, fed continuously with thickened ore pulp.

drum horn

Wrought-iron arms or spokes projecting beyond the surface or periphery of a flat-rope drum, between which the ropes coil or lap. See also: spider.


See: slope engineer.


The process of sounding the roof of a mine to discover whether rock is loose.


a. Loose coal or rock that produces a hollow, loose, open, weak, or dangerous sound when tapped with any hard substance to test condition of strata; said esp. of a mine roof.

b. The sound elicited when bad (loose) roof is tested by striking with a bar.

drum pulley

A pulley wheel used in place of a drum. See also: Koepe system.

drum rings

Cast-iron wheels, with projections, to which are bolted the staves or laggings forming the surface for the hoisting cable to wind upon. The outside rings are flanged, to prevent the cable from slipping off the drum.

drum runner

See: incline man.

drum separator

A slowly rotating cylindrical vessel that separates run-of-mine coal into clean coal, middlings, and refuse. It consists of different and adjustable specific gravities. The low gravity medium in one compartment separates a primary float product (clean coal), the sink material being lifted and sluiced into the second compartment where middlings and true sinks (stone) are separated.

drum shaft

See: caisson sinking.


a. An irregular cavity or opening in a vein or rock, having its interior surface or walls lined (encrusted) with small projecting crystals usually of the same minerals as those of the enclosing rock, and sometimes filled with water; e.g., a small solution cavity, a steam hole in lava, or a lithophysa in volcanic glass. CF: geode; miarolitic cavity; vug.

b. A mineral surface covered with small projecting crystals; specif. the crust or coating of crystals lining a druse in a rock, such as sparry calcite filling pore spaces in a limestone. Etymol: German. Adj: drusy.


a. Pertaining to a druse, or containing many druses. CF: miarolitic.

b. Pertaining to an insoluble residue or encrustation, esp. of quartz crystals; e.g., a drusy oolith covered with subhedral quartz.


a. Miner's changehouse, usually equipped with baths, lockup cubicles, and means of drying wet clothing.

b. A borehole in which no water is encountered or a borehole drilled without the use of water or other liquid as a circulation medium. Also called dry hole; duster. c. A borehole that did not encounter a mineral-, oil-, or gas-producing formation. Also called blank hole; dry hole; duster.

dry air

Air with no water vapor.

dry ash-free basis

An analysis expressed on the basis of a coal sample from which the total moisture and the ash have in theory been removed.

dry assay

Any type of assay procedure that does not involve liquid as a means of separation. CF: wet assay. See also: volumetric analysis.

dry block

The intentional act or process of running a core bit without circulating a drill fluid until the cuttings at and inside the bit wedge the core solidly inside the bit. Also called dry blocking.

dry blower

See: dry washer.

dry blowing

A process sometimes used where water is scarce. The separation of free gold from the accompanying finely divided material is effected by the use of air currents. See also: dry cleaning.

dry bone

See: dry-bone ore.

dry-bone ore

a. An earthy, friable, honeycombed variety of smithsonite in veins or beds in stratified calcareous rocks accompanying sulfides of zinc, iron, and lead.

b. A variety of hemimorphite. Syn: dry bone.

dry bulb temperature

Temperature indicated by a conventional dry thermometer; a measure of the sensible heat content of air.

drycleaned coal

Coal from which impurities have been removed mechanically without the use of liquid media.

dry cleaning

The cleaning of coal or ore by air currents as opposed to wet cleaning by water currents. Appliances for the dry cleaning of coal were first introduced about 1850 and since that date a variety of methods have been developed. See also: Kirkup table.

drycleaning table

An apparatus in which drycleaning is achieved by the application of air currents and agitation to a layer of feed of controlled depth on the table surface. See also: Kirkup table.

dry copper

Underpoled copper from which oxygen has been insufficiently removed when refining, so that it is undesirably brittle when worked cold or hot.

dry cyaniding

See: carbonitriding.

dry delta

See: alluvial cone; alluvial fan.

dry density

The weight of a unit volume of a dry sample of soil, after the latter has been heated at a temperature of 103 degrees C.

dry density/moisture ratio

The relationship between the density of a sample of soil in a dry state and its moisture content for a given degree of compaction. Such relationship can be determined from a curve that will reveal the optimum moisture content.

dry diggings

a. Placers not subject to overflow.

b. Placer mines or other mining districts where water is not available.

dry distillation

See: destructive distillation; pyrolysis.

dry drilling

Drilling operations in which the cuttings are lifted away from the bit and transported out of a borehole by a strong current of air or gas instead of a fluid. CF: dry running.

dry ductor

Compressed-air drill that traps and removes drilling dust instead of sludging it with added water.


An apparatus for drying coal. Dryers are of various types, such as revolving kilns, flash, and fluidized bed. See also: coal dryer; dehydrator.

dry fatigue

A condition often appearing in wire rope and often caused by shock loads in winding. These shock loads are produced by picking up the cage from the pit bottom with slack chains or by lifting heavy pithead gates or covers.

dry galvanizing

A process in which steel is fluxed in hot ammonium chloride and subsequently dried by hot air before being passed through a bath of molten zinc.

dry grinding

Any process of reducing particle size without the liquid medium. See also: grinding.

dry hole

A drill hole in which no water is used for drilling, as a hole driven upward. See also: blank hole.


See: changehouse.

dry ice

Solid carbon dioxide.

dry ice test

A test for detecting glass imitations; if a crystalline substance such as a gem mineral is placed on a piece of dry ice (solid CO (sub 2) ), a squeaking noise can be heard. This is not true of noncrystalline substances such as glass or plastic.

dry joint

Positive separation at the plane of contact between adjacent structural components to allow relative movement arising from differences in temperature or shrinkage.

dry kata cooling power

A measure of the rate of heat loss from the bulb of the kata thermometer. Although the cooling power as obtained by this instrument is not a measure of the capacity of an atmosphere to cool the human body, nevertheless, it is useful for comparing different atmospheres and provides a convenient index of the comfort condition of a working place in a mine. Experience indicates that a face will be reasonably comfortable for working if the dry kata cooling power is above 7 on the kata thermometer and the air velocity above 1 m/s. See also: dehumidification; effective temperature.

dry lake

See: playa.

dry milling

The comminution of materials in a suitable mill without the presence of a liquid, either by rods, balls, or pebbles, or autogenously, by the material itself; used if the subsequent process is a dry process.

dry mineral matter free basis

An analysis expressed on the basis of a coal sample from which the total moisture and the mineral matter have in theory been removed.

dry mining

a. In dry mining every effort is made to prevent the ventilating air picking up moisture, and throughout the ventilation circuit there is a wide gap between wet- and dry-bulb temperatures. Dry-bulb temperatures are therefore comparatively high.

b. Refers to the reasonably dry footing required for the equipment. Dry stripping and placer mining with standard earthmoving heavy equipment depends on good footing for the equipment and short hauls to keep costs in line. Syn: dry diggings.

dry ore

Said of lead or copper ore that contains precious metals (gold and silver) but insufficient lead or copper to be smelted without the addition of richer ore. See also: natural ore.

dry placer

Gold-bearing alluvial deposit found in arid regions. In some deposits the gold is in the cementing material that binds the gravel together. Because of the lack of water, various machines have been devised for the dry washing of these deposits; such machines commonly include some form of pulverizer and jigs or tables that use compressed air instead of water in their operation. Also called desert placer.

dry process

a. A method of treating ores by heat as in smelting; used in opposition to wet process, where the ore is brought into solution before extraction of the metal. See also: wet process.

b. The process of making Portland cement in which the raw materials are ground and burned dry. c. Process whereby dry powdered enameling materials are applied to a preheated surface. d. The method of preparation of a ceramic body wherein the constituents are blended dry, following which liquid may be added as required for subsequent processing.

dry puddling

A process of decarbonization on a siliceous hearth in which the conversion is effected rather by the flame than by the reaction of solid or fused materials. As the amount of carbon diminishes, the mass becomes fusible and begins to coagulate (come to nature), after which it is worked together into lumps (puddle balls, loups) and removed from the furnace to be hammered (shingled) or squeezed in the squeezer, which presses out the cinder, etc., and compacts the mass at welding heat, preparatory to rolling. Silicon and phosphorus are also largely removed by puddling, passing into the cinder. See also: puddling.

dry rotary drilling

See: dry drilling.

dry running

To unknowingly or knowingly drill with a bit when the flow of the coolant and cuttings-removal fluid past the bit has been inadvertently or deliberately cut off. CF: dry drilling.

dry sample

A sample obtained by drilling procedures in which water or other fluid is not circulated through the drill string and sampling device; hence the in situ characteristics of the sample have not been altered by being mixed with water or other fluid. CF: drive sample.

dry sampler

Various auger and/or tubular devices designed to obtain unwetted samples of soft rock material, such as clay, sand, soil, etc., by drilling procedures wherein water or other fluid is not circulated during the operation.

dry sand

a. A stratum of dry sand or sandstone encountered in well drilling. A nonproductive sandstone in oilfields.

b. Green sand dried in an oven to remove moisture and strengthen it (a dried-sand mold is a mold of green sand that is treated as above).

dry screening

The screening of solid materials of different sizes without the aid of water.

dry separation

a. The elimination of the small pieces of shale, pyrite, etc., from coal by a blast of air directed upon the screened coal. See also: wind method.

b. See: dedusting.

dry sweating

A process by which impure blister copper is exposed to long oxidizing heating below fusion point.

dry unit weight

The weight of soil solids per unit of total volume of soil mass. Also called unit dry weight. See also: unit weight.

dry wall stone

Thin-bedded limestone or sandstone suitable only for mortarless (dry) fencing or retaining walls.

dry wash

A wash that carries water only at infrequent intervals and for short periods, as after a heavy rainfall. CF: arroyo.

dry washer

a. A machine for extracting gold from dry gravel. It consists of a frame in which there is a rectangular bellows made of canvas; the upper part of the bellows is made by a plane set at an angle of about 20 degrees , across which are riffles. On the top of the machine is a screen on which gravel is shoveled. The screened gravel falls to a riffled plane from which it feeds to the riffles on the bellows. The screen and upper riffles are shaken by an eccentric worked with a crank, and the same crank actuates the bellows, which blow the dust from the gravel passing over the riffles. The gold is caught behind the riffles. Only gravel in which no moisture can be seen can be worked successfully by a dry washer.

b. A person who operates a dry washer. Syn: dry blower.

dry well

A deep hole, covered and usually lined or filled with rocks, that holds drainage water until it soaks into the ground.

dual-drive conveyor

A conveyor having a belt drive mechanism in which the conveyor belt is in contact with two drive pulleys, each of which is driven by a separate motor.

dual haulage

In strip mining, the use of two types of haulage at the same mine for transporting coal from the face to the preparation plant. Usually, coal is transported from the loading shovel to a transfer station by motorized units, and rail haulage is used to haul the coal from this point to the preparation plant.


A variety of dynamite consisting of four to five parts nitroglycerin, three parts sawdust, and two parts potassium nitrate.


See: cryptocrystalline.


Slate size of 24 in by 12 in (61.0 cm by 30.5 cm).


A fabric material, usually of woven cotton but of synthetic fibers also, used to construct conveyor belts and filter cloths.


The name given to a shaking-type combination loading and conveying device, so named from the shape of its loading end and which generally receives its motion from the shaking conveyor to which it is attached.

duckbill loader

See: shaker-shovel loader.

duckbill operator

In bituminous coal mining, one who operates a small power shovel that has a round-nosed scoop, called a duckbill, to load coal into cars in a mine.

duckbill pick

A duckbill-shaped coal-cutter pick that is forged by the roller type of machine from dies and is the type largely used today. The machine shaping of the pick ensures uniformity. It gives a constant clearance as the point wears down and is particularly suitable for fused-carbide tipping.


A pipe bend at the bottom of a shaft column or rising main fitted with a horizontal base sufficiently strong for the weight of the rising main to rest upon it. Also called duckfoot bend.

duckfoot bend

See: duckfoot.

duck machine

An arrangement of two boxes, one working within the other, for forcing air into mines.

duck's-nest tuyere

A tuyere having a cupped outlet.


An intimate mixture of pyrite and chalcocite or the matrix of a blackish copper ore containing grains of pyrite, Tennessee.


Abbrev. for dust concentrator, which is a device used to collect dry cuttings ejected from a borehole in which air or gas is used as a circulation medium.


A pipe or tubing used for auxiliary ventilation in a mine. Generally constructed of coated fabric, metal, or fiberglass.

duct fan

An axial-flow fan mounted in, or intended for mounting in, a section of duct. See also: tube-axial fan; vane-axial fan; mine ventilation auxiliary fan.


a. Said of certain metals and other substances that readily deform plastically.

b. Said of a rock that is able to sustain, under a given set of conditions, 5% to 10% deformation before fracturing or faulting. c. In mineralogy, capable of considerable deformation, esp. stretching, without breaking; said of several native metals and occasionally said of some tellurides and sulfides. d. Pertaining to a substance that readily deforms plastically. e. Capable of being permanently drawn out without breaking; such as, a ductile metal.

ductile cast iron

High-carbon ferrous product containing spheroidal graphite.

ductile crack propagation

Slow crack propagation that is accompanied by noticeable plastic deformation and requires energy to be supplied from outside the body.


The ability of a material to deform plastically without fracturing.


Sections of air duct. See also: ventilation tubing.


A calcian variety of annabergite, (Ni,Ca) (sub 3) (AsO (sub 4) ) (sub 2) .8H (sub 2) O, in which about one-third of the nickel is replaced by calcium; Pibble Mine, Scotland.


The amount of royalty or ore payable to the lord of the manor or owner of the soil.


a. Fine dry coal (usually anthracite) obtained from a coal-preparation plant. The size range is 3/16 to 0 in (4.8 to 0 mm). See also: gum; slack.

b. Smalls, usually with an upper size limit of 3/8 in (9.5 mm). c. Term used among British miners for a fine mixture of coal and rock. d. Aust. The fine coal left after separating the lumps; very fine screenings; dust. e. Coal dust and other unsaleable small coal produced in anthracite mines. See also: anthracite fines.


Aust. An unproductive claim or mine.

Duff furnace

A furnace used for the manufacture of producer gas.


A monoclinic mineral, Fe (super 2+) Fe (super 3+) (sub 4) (PO (sub 4) ) (sub 3) (OH) (sub 5) .2H (sub 2) O ; forms green botryoidal crusts commonly associated with limonite in gossans. Syn: kraurite; green iron ore.


A monoclinic mineral, Pb (sub 2) As (sub 2) S (sub 5) ; sp gr, 5.6; in crystalline dolomite in the Binnental, Switzerland.


An orthorhombic mineral, PbCu(AsO (sub 4) )(OH) ; adelite group; sp gr, 6.4; at Tsumeb, Namibia.


A gold-washing dish used in Jashpur, India.


Som. A method of hoisting coal on an incline from the working face to the pit bottom by a rope attached to the winding engine at surface in such a way that while the cage is going up, the empty trams are running down the incline, and as the cage descends the loaded cars are brought up to the shaft.


a. Brist. Slack ventilation; insufficient air in a mine.

b. As applied to the degree of luster of minerals, means those minerals in which there is a total absence of luster, as chalk or kaolin.

dull attritus

A field term denoting the degree of luster of attrital coal as it compares to the brilliant luster of vitrain associated in the same locality. CF: bright attritus.

dull-banded coal

Coal consisting of vitrain and durain with more or less minor clarain and minor fusain.

dull coal

a. Any coal that absorbs the greater part of incident light instead of reflecting it. Stopes recognizes two kinds of dull coal--durain and fusain.

b. The constituent of banded coal macroscopically somewhat grayish in color, of a dull appearance, less compact than bright coal, and breaking with a rather irregular fracture. It consists mainly of two kinds of material; thin black bands interlayed by a lighter colored granular-appearing matter. Microscopically, it consists of smaller anthraxylon constituents together with a few other constituents, such as cuticles and barklike constituents embedded in a general matrix, the attritus. c. A variety of banded coal containing from 20% to 0% of pure, bright ingredients (vitrain, clarain, and fusain), the remainder consisting of clarodurain and durain.


A Malayan term for hardwood pan shaped like a section of the surface of a sphere and used as a miner's pan in prospecting, sample washing, and manual concentration of cassiterite. See also: pan.

dumb barge

A barge similar to a hopper barge, frequently used to take dredged material from a dredger to the dumping ground.


Choked or clogged, as a grate or sieve in which the ore is beneficiated.

dumb drift

a. A passage leading from an airway to a point in a shaft some distance above an inset to allow the ventilating current to bypass a station where skips or cages are loaded.

b. A roadway driven through the waste in longwall mining to provide packing material.

dumb furnace

A ventilating furnace in which the foul flammable air from remote parts of the mine enters the upcast higher up than the hot gases from the fire.

dumb screen

A chute in which there are no meshes or bars for separating the coal, and down which the run-of-mine coal passes from the tubs direct to the railway wagon. It is used in small mines where the coal is sold as loaded underground or at mines where the coal is conveyed by wagon to a central coal-preparation plant.


a. A short piece of core or core-size cylinder of rubber or other material placed in the core lifter in an empty core barrel to guide the first part of a newly cut core into the core lifter. Syn: guide core.

b. A cathode, usually corrugated to give variable current densities, which is plated at low current densities to remove preferentially impurities from a plating solution. c. A substitute cathode that is used during adjustment of operating conditions.

dummy elevator

A second elevator for boosting tailings to higher stacking levels.

dummy gate

N. of Eng. A small gate made on the face between the mother gate and tailgate for the purpose of getting stone to make strip packs for roof support (when goaf roof is supported and not allowed to cave).

dummy locator

One whose name is used by a locator to secure for the latter's benefit a greater area of mineral land than is allowed by law to be appropriated by a single person, and any location made in pursuance of such a scheme or device is without legal support and void.

dummy maker

In bituminous coal mining, a laborer who fills paper cartridges (cylinders) with clay, adobe, or rock dust, used for stemming (tamping clay or other material on top of explosives) drill holes in the working face to be blasted down.


A monoclinic mineral, Pb (sub 2) (UO (sub 2) ) (sub 3) O (sub 2) (PO (sub 4) ) (sub 2) .5H (sub 2) O ; yellow; secondary; radioactive.


An orthorhombic mineral, Al (sub 7) (BO (sub 3) )(SiO (sub 4) ) (sub 3) O (sub 3) ; fibrous or radiating; Mohs hardness, 7 to 8-1/2; in schists, gneisses, and pegmatite dikes.

dumortierite quartz

A massive, blue, violet-blue, or blue-black, opaque variety of quartz colored by intergrown crystals of dumortierite.

Dumoulin process

A method whereby copper is deposited on a rotating mandrel and later stripped off as a long strip, which is then drawn into wire without recasting.


a. A pile or heap of ore, coal, or waste at a mine.

b. The point where a face conveyor discharges its coal into mine cars. c. The tipple by which the cars are dumped. CF: tipple. d. The fall available for disposal of refuse at the mouth of a mine.

dump bailer

A bailer used in borehole-cementation work, provided with a valving device that empties the contents of the bailer (cement) at the bottom of a borehole. Also called liquid dump bailer.


A cart having a body that can be tilted or a bottom opening downward for emptying the contents without handling.

dumped fill

Excavated material transported and dumped in a heap, generally to preestablished lines and grades. Should be kept free of tree stumps, organic matter, trash, and sod if any future use of the filled area is contemplated.

dump equipment

One of many conveyances that carry and then dump rock or ore. Generally trucks in surface mining and shuttle cars in underground mining.


A wheeled car with an elevated turntable on which is a track. A mine car run on the upper, horizontally revolving track can be dumped sidewise or endwise. Also called hurdy girdy.

dump hook

A chain grabhook having a lever attachment for releasing it.

dump house

The building where the loaded mine cars are emptied into the chutes.

dumping bucket

A lifting bucket with a tilt or drop bottom.

dumping wagon

See: dumper.

dump leaching

Term applied to dissolving and recovering minerals from subore-grade materials from a mine dump. The dump is irrigated with water, sometimes acidified, which percolates into and through the dump, and runoff from the bottom of the dump is collected and mineral in solution is recovered by a chemical reaction. Commonly used to recover gold and copper. See also: heap leaching.


A mass of ground left undisturbed until the final stages of excavation, when it is removed. In the intermediate stages it may be used as a support for timbering to the excavations.

dump motorman

In bituminous coal mining, one who operates a mine locomotive (motor) to haul cars of dirt, rock, slate, or other refuse to the dump at the surface of an underground mine. Also called dirt-dump engineer; refuse engineer.

dump room

Space available for disposing of waste from a mine.

dump skip

A skip with an attachment that dumps the load automatically.

dump wagon

A large-capacity side-, bottom-, or end-discharge wagon (or skip) on tired wheels or crawler tracks; usually tractor towed.


An orthorhombic mineral, PbAl (sub 2) (CO (sub 3) (sub ) ) (sub 2) (OH) (sub 4) .H (sub 2) O ; secondary; in aggregate tufts of minute, radiating needles.


Peridotite in which the mafic mineral is almost entirely olivine, with accessory chromite almost always present. Named by Hochstetter in 1864 from Dun Mountain, New Zealand.

Dunkard series

Continental strata, including thin coal seams, similar to the Pennsylvanian, but of Permian age, occurring in North America. Strata of the same age are marine in Kansas, but include marginal red beds with gypsum, and thick salt deposits were formed later in the Kansas Basin.


A term used in SW England for a shale or massive clay associated with coal.


a. A term used near Matlock, England, for a hard granular yellowish or cream-colored magnesian limestone.

b. A term used in Wales for a hard fireclay or underclay, and in England for a shale.


Trademark for high-velocity permissible explosives furnished in seven grades based upon velocity and cartridge count; poor water resistance. Used for mining coal where lump coal is not a factor.

duoflex checker system

A checker arrangement for hot-blast stoves. The gas used is only partially cleaned and may contain from 0.5 to 1.5 g of dust per cubic meter of gas. The top zone of the checkers is formed of straight-walled vertical passages, and the middle zone of vertical passages in each of which two opposite walls are continuously curved and the other two are straight, while the bottom zone is formed of vertical passages in each of which all four walls are continuously curved.

duplex breaker

A breaker having more than one crushing chamber.

duplex channeler

A type of channeling machine that cuts two channels simultaneously.

duplex compressor

Two compressors, side by side, and made in the combination of simple steam and simple air cylinder, simple steam and compound air cylinders, or compound steam and compound air cylinders. See also: air-conditioning process.

duplexing (duplex process)

Any two-furnace melting or refining process.

duplex pick

A coal-cutter pick that allows a cut to be made in either direction without turning the pick. It is drop forged with a tip of fused tungsten carbide.

duplex pump

A positive displacement pump with two water or liquid cylinders side by side and geared so that the piston strokes in the cylinders alternate. Such a pump may be either single or double action, depending on the number and placement of intake and discharge valves on the cylinder and may be designed so as to deliver a low volume of liquid at high pressures. CF: centrifugal pump; triplex pump.

duplex pump

Displacement pump for handling pulps. Two cylinders are so geared that one piston falls while other rises. Can lift small tonnages to good heights.

duplex steel

Steel produced by first refining it in a Bessemer converter and afterward completing the process in an open-hearth furnace.

duplex Talbot process

A combination of the duplex and the Talbot continuous process. Molten steel from the Bessemer converter, already freed of its carbon, silicon, and manganese contents, is charged into the Talbot furnace. As this molten steel is poured through the oxidized slag, the phosphorus is removed almost immediately. Sometimes pig iron is poured in afterwards, which raises the carbon content of the bath and aids in its deoxidation. A portion of the heat can usually be tapped about an hour after this addition.

duplex wire

Two insulated-copper leading wires wrapped together with paraffined cotton covering.

duplicate sampling

The placing of alternate samples of coal or ore in different containers that are then analyzed separately. Each container thus holds a representative subsample taken at intervals throughout the sampling intervals or period.

Dupont process

A heavy-liquid minerals separation process in which organic liquids of high specific gravity, known as parting liquids, are used. With sp gr 1.00 to 2.96 and very low viscosities, they serve ideally for the medium in the sink-and-float separation of solid materials. This process is used to clean run-of-mine anthracite, refuse banks, or mixtures of the two. The sizes of anthracite coal that can be cleaned are No. 1 buckwheat, and larger. This includes sizes up through broken. See also: parting liquid.


a. The capacity of a gem to withstand abrasion, impact, and chemical alteration.

b. The rate of deterioration of foundry sand due to dehydration of its contained clay.


The term was introduced by M.C. Stopes in 1919 to designate the macroscopically recognizable dull bands in coals. Bands of durain are characterized by their gray to brownish-black color and rough surface with dull or faintly greasy luster; reflection is diffuse; they are markedly less fissured than bands of vitrain, and generally show granular fracture. In humic coals, durain occurs in bands up to many centimeters in thickness. Widely distributed, but with exceptions not abundant. CF: fusain; vitrain. See also: attritus; hards.


A monoclinic mineral, NaAl(AsO (sub 4) )F ; occurs with cassiterite at the Barranca tin mine, Durango, Mexico.


A general term for a hard crust on the surface of, or layer in the upper horizons of, a soil in a semiarid climate. It is formed by the accumulation of soluble minerals deposited by mineral-bearing waters that move upward by capillary action and evaporate during the dry season. See also: ferricrete; silcrete; calcrete; caliche. Etymol: Latin durus, hard, + crust. CF: hardpan.


A process of electrodepositing hard chromium on the wearing surfaces of parts as a protection against wear by friction.


a. Term for the microlithotype consisting principally of the following groups of macerals: inertinite (micrinite, fusinite, semifusinite, and sclerotinite) and exinite, particularly sporinite. Durite contains at least 95% inertinite and exinite. The proportions of these two groups of macerals may vary widely, but each must be greater than the proportions of vitrinite and neither must exceed 95%. Durite E and durite I connote durites rich in exinite and inertinite, respectively. It is found in many coals, in fairly thick bands, principally in durains and the duller type of clarain, generally common.

b. A coal microlithotype that contains a combination of inertinite and exinite totalling at least 95%, and containing more of each than of vitrinite. CF: durain.


A rock-type coal consisting of the maceral vitrinite (telinite or collinite) and large quantities of other macerals, mainly micrinite and exinite. Micrinite is present in lesser quantities than is true with clarodurain. CF: clarodurain.


a. This term was introduced in 1956 by the Nomenclature Subcommittee of the International Committee for Coal Petrology to designate the microlithotype with maceral composition between those of clarite and durite but closer to clarite than durite. Further specification is that the proportion of vitrinite must exceed that of inertinite. It occurs in fairly thick bands, and is widely distributed and, like clarodurite, is a common constituent of most humic coals. The technological properties of duroclarite are intermediate between those of clarite and durite, but because of the predominance of vitrinite over inertinite they resemble those of clarite more closely than those of durite.

b. Coal microlithotype intermediate between clarite and durite; vitrinite, exinite, and inertinite each exceed 5% and the last is less abundant than vitrinite. c. A coal microlithotype containing at least 5% each of vitrinite, exinite, and inertinite, with more vitrinite than inertinite and exinite. It is a variety of trimacerite, intermediate in composition between clarite and durite, but closer to clarite. CF: clarodurite.


Vitrain with minute inclusions of durain. CF: vitrodurain.

Durville process

A casting process that involves rigid attachment of the mold in an inverted position above the crucible. The melt is poured by tilting the entire assembly, causing the metal to flow along a connecting launder and down the side of the mold.


A trigonal mineral, BaFe (sub 3) (AsO (sub 4) ) (sub 2) (OH) (sub 5) ; crandallite group; forms green to yellow-green rosettes or crusts.


See: ash.

dust barrier

See: stone-dust barrier.

dust catcher

a. A device attached to the collar of a borehole to catch or collect dry, dustlike rock particles produced in dry-drilling a borehole. CF: ducon.

b. Any device in which dust is collected or extracted from furnaces, gases, etc.

dust chamber

a. An enclosed flue or chamber filled with deflectors, in which the products of combustion from an ore-roasting furnace are passed, the heavier and more valuable portion settling in the dust chamber and the volatile portions passing out through the chimney or other escape.

b. Room air system, flue or dust extractor, where larger particles can drop out of stream of gas and be periodically removed. Used in conjunction with cyclones, electrostatic precipitators, and bag filters.

dust cloud

Coal or other dust particles carried in suspension in the air by currents and eddies.

dust cloud flammability

The flammability of a coal-dust cloud is its ability to promote spreading flames away from the source of ignition.

dust collection

Removal from atmosphere of mill or from transfer points where dust is thrown up. Partially closed ventilating systems are used, which incorporate bag filters, Cottrells, cyclones, washing chambers, and spray towers.

dust collector

a. A device used on a roof bolting machine while in operation for separating solid particles from air and accumulating them in a form convenient for handling.

b. Device used to collect dust produced in percussion rock drilling, this device has an exhauster operated with compressed air from the available air system. Air laden with dust and cutting is drawn from the boreholes through the bit holes, the hollow drill steel, the adapter, and the suction hose into a filter. The filtered air is excavated with the spent compressed air through an exhaust port, and dust and cuttings settle in a removable storage tank.

dust consolidation

The binding of coal dust on roadway surfaces to prevent it becoming airborne by any disturbance. One method is to spread calcium chloride over the dust so that it absorbs water and forms a pasty cake that does not rise into suspension when workers travel on the roadway. See also: stone dust.

dust counter

A portable apparatus (as the Koltze tube, an impinger, etc.) used to measure dust concentration in a mine or mill, as a health precaution.

dust explosion

An explosion which consists of a sudden pressure rise caused by the very rapid combustion of airborne dust. Ignition of suspensions of combustible dusts can occur in the following ways: (1) initiation by flame or spark, (2) propagation by a gas explosion or blasting, and (3) spontaneous combustion. Little is known about the last-named mechanism, which is relatively rare in mines. The most frequent causes of major coal mine explosions in the United States today are electric arcs, open flames, and explosives. See also: coal-dust explosion.

dust extraction

The removal of solid particles suspended in gas or ambient air.

dust extractor

An appliance to collect or precipitate suspended dust. Dust extraction is often necessary at coal-preparation plants, loading stations, and also underground. The appliance may be a cyclone, fabric filter, spray tower, scrubber, or an electrostatic separator. See also: dust precipitator; dust trap.

dust firing

The burning of coal dust in the laboratory of the furnace.

dust-free conditions

In Great Britain, the arbitrary standards laid down by the National Coal Board in 1949 as representing comparative dust-free conditions in coal mines. These are as follows: stone dust, 450 particles/cm (super 3) (size range, 0.5 to 5.0 mu m); anthracite, 650 particles/cm (super 3) (size range, 1 to 5 mu m); and coal, 850 particles/cm (super 3) (size range, 1 to 5 mu m).

dust gold

Pieces of gold under 2 to 3 pennyweights (3.1 to 4.7 g); very fine gold.

dust hopper

A hopper placed underneath the scraper, rapping roller, or other belt cleaner, to collect the dust and dirt as it is removed from the belt; any tank or vessel to receive and retain dust.

dusting loss

a. Shortfall in expected weight of sands or finely ground materials due to wind action or loss when transported in open trucks.

b. In laboratory sampling, the loss of part of a sample undergoing test, through leakage of particles into the atmosphere.

dust-laying oil

Crude oils, heavy asphalt oils, tars, solutions of petroleum asphalt in gas oils, liquid asphalt, and emulsions of oils and water, used for laying dust on roads.

dustless zone

A section of the mine entry from which dust has been removed as completely as possible by scraping or sweeping, aided by a compressed-air blast.


One who dumps the dust catcher or loads the dust at blast furnaces.

dustpan dredge

A dredge containing a suction head that is pulled over the underwater ground much as a dustpan would be. About 8 in (20 cm) high, the dustpan may be from 20 to 40 ft (3.6 to 7.1 m) long and is supplied with jets along its face to stir up the bottom surface.

dust plan

A plan kept with the book in which stone-dust samples are recorded. It shows the sampling zones in each roadway, distinguished by color, letter, number, or mark, and identified with that roadway.


A vertical iron plate, supporting the slag runner of an iron blast furnace.

dust precipitator

On a large scale, sinter plant gas may be cleaned by precipitators with very high efficiencies. The dust is precipitated in a dry state, suitable for pelletizing and feeding back onto the sinter strand. See also: thermal precipitator.


A surface treatment, as with oil or calcium chloride solution, to prevent or reduce the dustiness of coal in handling.

dust sampling

The taking of air samples to assess their degree of dustiness, either on a mass basis or on particle count in a known volume of air. Numerous instruments have been developed for this purpose. Dust sampling is also necessary to assess the efficiency of stone dusting. See also: sampling instrument; konimeter; size selector; thermal precipitator; tyndallometer.

dust-sampling impinger

A portable instrument for collecting dust samples so that corrective measures can be taken for dust control and the prevention of respiratory diseases. Dust-laden air is impinged in sampling flasks by manual, compressed air, or electrical suction devices. Dust counts are made from the collected air at laboratories with microscopes and counting cells.

dust suppression

The prevention or reduction of the dispersion of dust into the air, for example, by water sprays.

dust-suppression jib

A coal-cutter jib designed to conduct water through ducts, or other arrangement, to the back of the kerf, to suppress dust and reduce the gas-ignition hazard. See also: whale-type jib.

dust-suppression person

A person employed in coal mines to apply measures to allay coal dust on mine roadways and along the coal faces. The worker also may be in charge of dust suppression in rock drivages. See also: rock dust.

dust-suppression system

With this system, dust can be suppressed before it becomes airborne. A series of nozzles discharge a chemical compound in a fine spray to materially reduce the amount of water or other liquids necessary to saturate fly ash and eliminate dust. The compound also aids in the diffusion of the liquid dust suppressant, allowing it to penetrate deeper into the material. This system can be used at any point in the handling of bulk materials, wherever dust is a hazard.

dust trap

An appliance for the dry collection of dust during drilling in rock. The rock chippings, dust, and air are sucked from the borehole through a rubber hose to a drum-type container with filters. The drum is discharged and the filters renewed periodically. In some of the newer types, the dust is extracted through the hollow drill rods. See also: C.P. Hemborn dust extractor; Holman dust extractor.

dust wetting agent

Chemical compounds that aid in the control of dry dusts such as coal and silica to help prevent explosions and respiratory injury to workers. These compounds are of two types. One type is used in a dry state and controls dust by absorbing moisture from the air. The second type is an agent for increasing the wetting effectiveness of water by breaking the surface tension and permitting the water-compound mixture to thoroughly cover the treated area.

Dutch drop

A haulage term for flying switch.

Dutch State Mines Process

A sink-float process used principally for coal cleaning. The process uses a water suspension of loess (a natural claylike material) in special trough-type separators provided with a clean coal weir and a reject drag conveyor.

dutch twill

A type of wire cloth weave; a weave in which the first shute wire crosses over the first and second warp wires, under the third and fourth warp wires, and the second shute wire crosses under the first warp wire, over the second and third warp wires, under the fourth and fifth, etc.


A monoclinic mineral, VO(OH) (sub 2) ; forms minute pale-brown scales as an alteration of montroseite in sandstone on the Colorado Plateau.

duty of giants

The amount of gravel that can be moved by a water cannon, or giant, in a 24-h day by a specified flow of water. The duty of giants varies considerably with local conditions, such as the height of the gravel banks, the nature of the gravel bedrock, head of water obtainable, size of jet, etc.

duty of the miner's inch

The number of cubic yards of gravel that can be broken down and sent through the sluice by 1 miner's inch of water for 24 h. It depends upon the height of the bank, the character of the gravel and the bedrock, the grade of the bedrock, the type of sluice, and the pressure of the water. In well-rounded gravel without large stones, the duty of the miner's inch is from 4.5 to 6 yd (super 3) (3.3 to 4.6 m (super 3) ) of gravel for 24 h. Under less favorable conditions, the duty may range from 2.8 to 4.6 yd (super 3) (2.1 to 3.5 m (super 3) ) for 24 h. See also: miner's inch.


An opaque, dark-brown variety of retinite containing about 0.5% sulfur in lignite at Dux, Bohemia, Czech Republic; is similar to muckite, walchowite, and neudorfite.

dwarf Brinell tester

A portable ball hardness tester in which the load is applied by means of a vise or lever. It carries a special lens for measuring the impression's diameter and from which the Brinell hardness value can be read directly.

Dwight-Lloyd machine

Sintering machine in which feed moves continuously on articulated grates pulled along by chains in belt-conveyor fashion. Controlled combustion on these grates causes the minerals to sinter.

Dwight-Lloyd process

Blast roasting in which air currents are drawn downward through the ore mass.

Dwight-Lloyd roaster

A multihearthed circular furnace, through which horizontal rabbles revolve and move the feed across each hearth, so that it falls peripherally to the one below and then works inward to central discharge for next hearth below. Rising heat and air provide the roasting conditions.


An orthorhombic mineral, Ag (sub 3) Sb ; metallic silver-white, commonly tarnished; sp gr, 9.74; in veins with galena, native silver, and silver sulfosalts; an ore of silver.

dyed stones

Minerals artificially dyed to improve their color or to imitate a more valuable stone; they usually fade or discolor and may include chalcedony, turquoise, jadeite, opal, serpentine, and alabaster.

dye line print

A contact print that has largely replaced the blueprints.


The British spelling of dike.

dynamic braking

A method of retarding an electric winder or haulage, in which a direct current is injected into the alternating-current winder motor stator during the deceleration period; the motor then acts as an alternator, and the negative load of the winding cycle is absorbed as electric power and wasted as heat in the controller. See also: electric braking.

dynamic damping

Usually found in seismographs or seismometers where damping of motion is desired that is in proportion to the velocity of the moving mass.

dynamic geology

A general term for the branch of geology that deals with the causes and processes of geologic phenomena; physical geology.

dynamic head

The head of fluid that would statically produce the pressure of a given moving fluid. Syn: velocity head.

dynamic load

a. An alternating or variable load.

b. See: live load.

dynamic metamorphism

The total of the processes and effects of orogenic movements and differential stresses in producing new rocks from old, with marked structural and mineralogical changes due to crushing and shearing at low temperatures and extensive recrystallization at higher temperatures. It may involve large areas of the Earth's crust, i.e., be regional in character. CF: dynamothermal metamorphism; regional metamorphism. Syn: dynamometamorphism.

dynamic method

See: modulus of elasticity.

dynamic penetration test

See: penetration test.

dynamic positioning

Maintainence of a drill ship's position through the use of outboard engines on opposite sides of the vessel. The position is maintained by automatic centering in a circle of sonar reflectors placed around the drilling target, either on the bottom or suspended by taut wire buoys. Several drilling ships are now equipped with this facility.

dynamic viscosity

See: viscosity coefficient.


a. An industrial explosive that is detonated by blasting caps. The principal explosive ingredient is nitroglycerin. Diethyleneglycol dinitrate, which is also explosive, is often added as a freezing-point depressant. A dope, such as wood pulp, and an antacid, such as calcium carbonate, are also essential. See also: blasting gelatin. Oxidizers, such as ammonium nitrate, and fuels, such as vegetable fiber, are usually added.

b. A general term for detonable explosives in which the principal constituent, nitroglycerin, is contained within an absorbent substance. "Detonable" is a significant part of the definition since there are compositions that contain significant amounts of nitroglycerin but that are not detonable and are not considered to be dynamite.

dynamo exploder

A powerful exploder usually operated by a vertical rack, which, on a downward movement, drives an armature. At the end of the stroke of the rack bar an internal short-circuiting device opens and the current generated by the rapidly revolving armature passes into the shot-firing circuit. See also: blasting machine; exploder.


Augen gneiss containing much microline and orthoclase.


Dynamic metamorphism.


Appliance used in engineering to measure power as output, input, or transitional.


A permissible explosive of the ammonium nitrate group.

dynamothermal metamorphism

A common type of metamorphism involving the effects of directed pressures and shearing stress as well as a wide range of confining pressures and temperatures. It is related both geographically and genetically to large orogenic belts, and hence is regional in character. CF: regional metamorphism; dynamic metamorphism.

Dynobel No. 2

A high-strength, low-density permitted explosive; no water resistance. It is used for coal blasting in a machine-cut seam of medium hardness in dry conditions.


A natural antimonide of silver, Ag (sub 3) Sb ; color and streak, silver-white; luster, metallic; usually tarnished; Mohs hardness, 3.5 to 4; sp gr, 9.74; found in Germany, France, and Canada. An ore of silver. Syn: antimonial silver.


See: microcrystalline.


A brown variety of gahnite containing manganese and iron in Massachusetts and New Jersey.


See: dysprosium oxide.

dysprosium oxide

A rare-earth oxide; white; Dy (sub 2) O (sub 3) ; isometric; sp gr, 7.81 (at 27 degrees C); and melting point, 2,340+ or -10 degrees C. Used as a nuclear-reactor control-rod component and a neutron-density indicator. Syn: dysprosia.

dystome spar

See: datolite.


Having an imperfect fracture or cleavage.


An isometric mineral, In(OH) (sub 3) ; an alteration of indite; associated with cassiterite ores.


Possibly an amorphous lead rhenium sulfide found in the Dzhezkazgab copper ores, Kazakhstan.