Appendix:Dictionary of Mining, Mineral, and Related Terms/D/4

dore
 * Gold and silver bullion that remains in a cupelling furnace after the lead has been oxidized and skimmed off. Syn: dore bullion.

dore bullion
 * See: dore.

dore metal
 * See: dore silver.

dore silver
 * Crude silver containing a small amount of gold, obtained after removing lead in a cupelling furnace. Syn: dore bullion; dore metal.

dornick
 * a. A piece of rock of approx. fist size.

b. A boulder of iron ore.

Dorr mill
 * A tube mill designed for operation as a closed-circuit wet-grinding unit. See also: tube mill.

Dorr rake classifier
 * A mechanical classifier consisting of an inclined settling tank and a rake-type conveying agitating mechanism. Feed introduced at the low end of the tank flows over a distributing apron toward the high end of the tank. The heavier materials of sand size settle into the rake zone and are raked up the slope and out the tank; slime and finer sands are carried over the rear wall in suspension.

Dosco miner
 * A heavy, crawler-tracked, 200-hp (149-kW) cutter loader designed for longwall faces in seams over 4-1/2 ft (1.37 m) thick, and takes a buttock 5 ft (1.52 m) wide. The maximum cutting height is 7-1/2 ft (2.29 m). Dimensions: length 17-3/4 ft (5.41 m), width 4-1/2 ft (1.37 m), and height 3-3/4 ft (1.14 m). The cutterhead consists of seven cutter chains mounted side by side and can be moved up and down radially to cut the coal from roof to floor. It delivers the coal onto the face conveyor by a short cross conveyor. Capacity is more than 400 st (363 t) per machine and more than 4 st (3.63 t) output per worker per shift.

dose
 * a. A special charge used in a blast furnace, designed to cure furnace troubles.

b. The amount of ionizing radiation energy absorbed per unit mass of irradiated material at a specific location, such as a part of the human body. Measured in reps, rems, and rads.

dot chart
 * a. A graphic aid used in the correction of station gravity for terrain effect, or for computing gravity effects of irregular masses. It can also be used in magnetic interpretation.

b. A transparent graph-type chart used in the calculation of the gravity effects of various structures. The dots on the chart represent unit areas.

double
 * In rotary drilling, two pieces of drill rod left fastened together during raising and lowering. Also called couple; couplet.

double
 * A. One of several terms (or letter symbols) used to designate medium-quality drill diamonds.

double-acting pump
 * Scot. A pump that discharges at both forward and backward stroke.

double-acting ram
 * See: two-way ram.

double-action press
 * A press handling two operations each revolution. It carries two rams, one inside the other, so actuated that one motion immediately follows the other.

double-action pump
 * A pump whose water cylinders are equipped with intake and discharge valves at each end; hence liquid is delivered by the pump on both the forward and the backward strokes of the pump piston.

double bank
 * a. To take up a claim parallel with and adjoining another claim containing an auriferous vein or deposit.

b. Working with double sets or relays of persons.

double block
 * a. A pair of multiple-sheave blocks reeved with rope or lines; a block and tackle.

b. Two pulleys or small sheaves mounted on a single shaft within a frame or shell.

double-burned
 * Burned at a high temperature. This does not mean two firings.

double-burned dolomite
 * a. Dolomite, with additions of oxides of iron, burned at a high temperature. This does not mean two firings.

b. Clinkered dolomite.

double core barrel
 * A core barrel with an inner tube to hold the core. The inner tube does not rotate during drilling, thereby giving a better core recovery. Syn: double-tube core barrel.

double crib
 * Eng. Two crib sets are placed back to back to form a two-compartment crib-lined raise. This technique is employed in weak ground in place of a double compartment separated by only a single dividing member.

double-cut sprocket
 * For double-pitch roller chains, a sprocket having two sets of effective teeth. Tooth spaces for the second set are located midway between those of the first set.

double-deck gangway
 * A method of silling or working out 10 ft (3 m) or so above the haulage level and forming a double-deck gangway. Chutes are constructed at intervals for ore transfer into mine cars.

double-double unit conveyor
 * A longwall conveyor layout in which the center or main gate serves two double units, one on each side. The gate belts from each double unit deliver the coal onto cross-gate belts, which in turn deliver to the main gate conveyor and then by trunk conveyor or cars to the pit bottom.

double drum
 * Hoisting device having two cable spools or drums rotating in opposite directions.

double-drum hoist
 * A hoist with two drums that can be driven separately or together by a clutch. See also: main-and-tail haulage.

double-duo mill
 * Has two pairs of rolls, mounted in one stand, one pair of rolls being higher than, and in advance of the other.

double-ended
 * A term applied to any cutter loader that can cut both ways on a longwall face without turning at each end. This requires cutting units at both ends of the machine and duplication of other essential parts.

double-ended pick
 * A diamond-shaped coal-cutter pick that is held in a special holder and chain. Both ends of the pick are used and then discarded. The type is used widely in the United States. See also: coal-cutter pick.

double-engine plane
 * Loads are raised or lowered on a slope by a stationary engine and wire rope, as in an inclined shaft. There is a double track, or three rails and turnout; the descending trip assists the engine to raise the ascending trip, thus eliminating dead load, except rope.

double entry
 * a. A pair of entries in flat or gently dipping coal so laid out that rooms can be driven from both entries; twin entries. See also: entry.

b. A system of ventilation by which the air current is brought into the rooms through one entry and out through a parallel entry or air course. c. See: main entry.

double-entry room-and-pillar mining
 * See: room-and-pillar.

double-entry zone test
 * A test in which coal dust is placed in each of two connected parallel entries.

doubleheader
 * Applied to quarry equipment consisting of two independent channeling machines on a single truck, operated by one person.

double headings
 * The driving of two coal headings, parallel and side by side, for development purposes. Usually a pillar 10 to 20 yd (9.14 to 18.29 m) wide is left between them. Formerly it was the practice at many coal mines to drive only one heading from which the stalls were turned off right and left. Two headings simplify ventilation and provide a second egress in an emergency.

double helical bag conveyor
 * Closely spaced parallel tubes with right- and left-hand rounded helical threads rotating in opposite directions, on which bags or other objects are carried while being conveyed. Syn: helical bag conveyor.

double-inlet fan
 * A centrifugal fan in which air enters the impeller on both sides. Also called double-width fan.

double jack
 * a. A two-hand heavy hammer, usually weighing about 10 lb (4.54 kg). CF: single jack.

b. A double or twin-screw drill column.

double jigback
 * An aerial ropeway in which two parallel track ropes are used, each carrying a carriage.

double-leg bucket elevator
 * A type of bucket elevator having the carrying and return runs enclosed in separate casings between the head and boot. See also: bucket elevator.

double leg en masse conveyor
 * A conveyor or elevator in which the carrying and return runs are operated in separated parallel and adjacent casings.

double load
 * A charge in a borehole separated by a quantity of inert material for the purpose of distributing the effect, or for preventing part of the charge blowing out at a seam or fissure, in which case the inert material is placed so as to include the seam.

double packing
 * A form of strip packing that removes the localized high roof pressure from the vicinity of a roadway into a region in the goaf. It consists of two parallel packs adjacent to, and on each side of, the roadway, with the packs immediately at the roadsides built of such a width as to offer less resistance than wider and stronger packs (called buttress packs) more remote from the roadway. The principle of double packing was developed by D.W. Phillips in Great Britain. See also: gate side pack; strip packing; yield-pillar system. CF: single packing.

double parting
 * A bypass for mine cars. See also: junction.

double-pitch roller chain
 * A roller chain having double the pitch of a standard roller chain, but otherwise having standard pins, bushings, and rollers.

double-pulley-drive conveyor
 * A conveyor in which power is transmitted to the belt by two pulleys.

double-refracting spar
 * See: Iceland spar.

double refraction
 * Refraction shown by certain crystals that split the incident ray into two refracted rays, polarized in perpendicular planes. See also: birefringence.

double-roll breaker
 * a. A coalbreaker that relies on the impact of special teeth for the bulk of reducing, rather than on the compression between the rolls. An important feature is adjustment, which may be made during operation. The machines are flexible enough to produce top size ranging from 6 to 14 in (15.4 to 35.56 cm).

b. See: double-roll crusher.

double-roll crusher
 * A machine for breaking down ore, rock, or coal and to discharge the crushed material below. See also: spring-roll crusher; roll crusher; single-roll crusher.

double-roll press
 * A press in which pressure is applied by the mating of one or more pairs of indented rolls of equal diameter, revolving in opposite directions. Syn: Belgian press.

double-room system
 * See: room-and-pillar.

double-round nose
 * The cross-sectional view of the cutting face portion of a coring bit when its profile is a full half circle, the radius of which is one-half the wall thickness or kerf of the bit face. CF: single-round nose.

double setting
 * A leveling procedure whereby observations are duplicated by resetting the instrument to detect errors of measurement immediately. Also called dual setting.

double-shift places
 * At collieries where there is only one recognized coal-winning shift in 24 h, it is a general practice to have double shifts (and sometimes treble) of workers in development headings that require a speedy advance.

double-spaced neutron log
 * This method employs two neutron logging tools with different spacings between the source and the detector or two detectors in the same tool at different spacings. The spacings usually differ by 6 to 10 in (15.24 to 25.4 cm). The long-spaced log is run slowly and with a large time constant so that its statistical variation is not excessive, for the counting rate is much lower than that of the regular-spaced log. This technique has proved to be a potent technique for discriminating gas sands from oil sands in Venezuela.

double spiral cut
 * A cylindrical drill-round cut whose spiral hole pattern gives the widest opening and permits opposite holes to be ignited successfully. This gives the best cleaning of the opening and safety in the advance is increased, since one section of the double spiral can give breakage irrespective of the other.

double stall
 * An earlier system of working thick seams in South Wales. Two narrow stalls are turned off the heading and after advancing some 8 to 12 yd (7.32 to 10.97 m) (so as to leave a pillar of coal next to the heading) are connected and the coal between them worked as a single face. Double stalls are intermediate between pillar-and-stall and longwall.

doublet
 * An assembled gem substitute composed of two pieces of material fused or cemented together. If both parts are of the species being imitated, it is a genuine doublet; if one part, it is a semigenuine doublet; if it contains no parts of the species being imitated, it is a false doublet; or if no part is a mineral, it is an imitation doublet. CF: triplet.

double-track portable switch
 * A tub-changing arrangement for a tunnel face. The double-track loop is superimposed on the tunnel track and equipped with ramps, clamps, and spring switches so arranged that the loaded cars take one track outward while the empties take the other track inward. Syn: portable shunt.

double-trolley system
 * A system of electric traction where, instead of the running rails, a second insulated contact wire is used for the return or negative current.

double-tube core barrel
 * A double-tube core barrel having the upper end of the inner tube coupled to the core-barrel head by means of an antifriction device, such as a roller or ball bearing; hence, the inner tube tends to remain stationary when the outer tube, which is rigidly coupled to the core-barrel head, is rotated.

double-unit conveyor
 * A longwall conveyor layout from 200 to 280 yd (183 to 256 m) long, developed between two tailgates with a main gate in the center of the face. The main gate conveyor is served by two face conveyors and may act as an intake or a return airway. The tailgates may serve as supply roads. See also: double-double unit conveyor; main gate.

double wedge cut
 * A drill-hole pattern consisting of a shallow wedge within an outer wedge, which is often used to obtain deep pull in hard rock. See also: wedge cut.

double wicket
 * A method of working in which rooms are driven from adjacent headings to meet at their extremities.

double working
 * N. of Eng. Two hewers (miners) working together in the same heading. Syn: hewing double.

doubly plunging fold
 * A fold that plunges in opposite directions from a central point. In a doubly plunging anticline, the plunge is away from this point; in a doubly plunging syncline, the plunge is toward this point.

doubly refractive
 * Causing double refraction. See also: birefringent.

dough
 * Alternate spelling of daugh.

doughnut
 * The cylinder of coal formed by a coal auger.

Douglas furnace
 * A horizontal, revolving cylindrical furnace having a central flue.

Douglas process
 * See: Hunt and Douglas process.

douk
 * Eng. A soft dark clay found in veins. Probably derived from the Saxon deagan, meaning to knead or mix with water. Syn: dowk.

dousing
 * See: dowsing.

dousing rod
 * Commonly used by drillers as a name applied to a wooden wand, rod, forked tree limb, or twig (usually witch hazel) supposedly useful in locating formations bearing water, oil, or mineral. Also called divining rod; doodlebug; dowsing rod.

doverite
 * See: synchysite.

Dow cell
 * The Dow electrolytic cell is a steel shell about 16 ft (4.88 m) long, 5 ft (1.52 m) wide, and 6 ft (1.83 m) deep. The electrolyte contains about 60% NaCl, 15% CaCl (sub 2), and 25% MgCl (sub 2) ; it is maintained at a temperature of 700 to 750 degrees C by controlled firing underneath the cell.

dowk
 * See: douk.

downbuckle
 * See: tectogene.

downcast
 * a. The shaft through which the fresh air is drawn or forced into the mine; the intake. See also: air shaft; intake.

b. That side of a fault on which the strata have been displaced downward in relation to the upthrow or upcast side.

downcast shaft
 * The shaft down which the fresh air enters the mine or workings. See also: upcast shaft.

downcomer
 * A pipe to conduct something downward, such as: (1) a pipe for leading the hot gases from the top of a blast furnace downward to the dust collectors and flue system, and (2) a tube larger in diameter than the water tubes in some water-tube boilers for conducting water from each top drum to a bottom drum under the influence of thermal circulation.

downdip
 * Parallel to or in general direction of the dip of a bed, rock stratum, or vein.

downdraft
 * A downward current of air or other gas (as in a mine shaft, kiln, or carburetor). Syn: downcast.

downdrift
 * In a mine drift, the direction of predominant water movement.

downhole
 * a. A borehole drilled at any angle inclined downward in a direction below the horizon.

b. adj. In a borehole; e.g., downhole equipment.--adv. Deeper; e.g., to perforate downhole.

downline
 * A line of detonating cord or plastic tubing in a blast hole that transmits the detonation from the trunkline or surface delay system down the hole to the primer.

downslope
 * The land surface between the projected outcrop of the lowest coalbed being mined along each highwall and a valley floor.

downspouts
 * Lanc. Pipes fixed down the side of a shaft for conducting water from one level or sump to another.

downstream face
 * The dry side of a dam.

down-the-hole drill
 * A percussive or hammer drill in which the bit-driven mechanism is located immediately behind the drill bit and is small enough in diameter to permit it to enter and follow the bit down into the hole drilled.

down-the-hole extensometer
 * A device used to measure differential strains in a drill hole.

downthrow
 * a. The downthrown side of a fault.

b. The amount of downward vertical displacement of a fault. CF: upthrow; heave.

downthrow fault
 * A fault that displaces the strata downward relative to the workings approaching it. It would be an upthrow fault to workings on the opposite side.

downthrow side
 * The lower side of a fault.

Downtonian
 * Uppermost Silurian or lowermost Devonian.

downward continuation
 * a. Interpretation method in which the values of a component of the magnetic field at lower levels are computed from the values at the surface.

b. The process of determining, from values measured at one level, the value of a potential (e.g., gravitational) field at a lower level.

downward course
 * In mining, the course of the vein from the surface downward. Also called course downward.

downward enrichment
 * See: supergene enrichment.

downward percolation
 * See: sand leaching.

Dow process
 * A process for the production of magnesium by electrolysis of molten magnesium chloride.

dowsing
 * The practice of locating ground water, mineral deposits, or other objects by means of a divining rod or a pendulum. A dowser may claim also to be able to diagnose diseases, determine the sex of unborn babies, etc. Syn: dousing; water witching. CF: rhabdomancy.

dowsing rod
 * See: divining rod.

Dowson gas
 * A mixture of producer gas and water gas obtained by passing steam and air over heated coal or coke in a Dowson producer.

Dowson producer
 * A furnace used for the manufacture of producer gas.

Dowty hydraulic tub retarder
 * A retarder that consists of lengths of steel channel with attached rubbing strips that operate on the face of the wheels above center. The action is controlled by a hydraulic cylinder containing opposed pistons. The hydraulic pressure is supplied from an accumulator in which pressure is maintained by means of a 5-hp (3.7-kW) electric motor-driven pump that is sufficient for 10 retarder unit.

Dowty prop
 * A prop that is in effect a self-contained hydraulic jack consisting of two tubes, the upper one telescoping into the lower. The upper (or inner) tube acts both as a reservoir for the oil and as a container for the pump, yield valve, and other accessories.

Dowty roofmaster
 * A self-contained, oil-operated steel support for use on a mechanized long-wall face. It has support frames constructed of rigid roof and floor members supported by yielding hydraulic props. Two- and three-prop units are connected alternately to the armored conveyor by means of jacks mounted in the floor members, to carry long and short cantilever roof beams, respectively. See also: self-advancing supports.

dozer
 * Abbrev. for bulldozer; shovel dozer. See also: bulldozer.

dozer shovel
 * A tractor equipped with a front-mounted bucket that can be used for pushing, digging, and truckloading.

dozzle
 * See: core.

D.P. reagents
 * Flotation reagents made by DuPont are D.P. 243, a 50% aqueous paste of lorolamine (lorol being a mixture of primary straight-chain alcohols) and D.P.Q., lauryl trimethyl ammonium bromide. Others include D.P.Q.B., D.P.C., D.P.N., and D.P.L.A.

dradge
 * Corn. The inferior portions of ore separated from the best ore by cobbing.

draft
 * A survey line in a traverse. Syn: leg.

draft engine
 * Corn. An engine used for pumping.

draft gage
 * An instrument used to measure the small pressure differentials below atmospheric; e.g., an inclined manometer to measure the pressure difference between a flue and the atmosphere for combustion control.

draft hole
 * An opening through which air is supplied to a furnace.

draftsman
 * In petroleum production, one who specializes in drawing subsurface contours in rock formations from the data obtained by a geophysical prospecting party. The draftsman plots maps and diagrams from computations based on recordings of seismograph, gravimeter, magnetometer, and other petroleum prospecting instruments, and from prospecting and surveying field notes.

drag
 * a. The frictional resistance offered to a current of air or water; resistance created by friction.

b. Fragments of ore torn from a lode by a fault. Such fragments are scattered along the line of the fault and are usually inclosed within crushed or brecciated pieces of the rock traversed by that fault. c. The flexuring of strata associated with faults. In a normal fault, the coal seam often bends upward on the downthrow side and downward on the upthrow side. Thus, drag is an indication of direction of displacement of the beds. Also called terminal curvature. See also: coal lead. d. In an inclined stope, the weight of the arch block is resolved into two components, one at right angles to the dip, which tends to close the opening, and one parallel to the dip, which tends to produce movement of the hanging wall with respect to the footwall. This movement is known as drag, or creep. Syn: creep. e. See also: drag ore. f. An appliance to be attached to the rear of a loaded train of cars to prevent the cars from running down the incline or grade in case the cable should break. See also: backstay. g. The uptilted or downtilted curve in rock beds or strata adjacent to a fault. h. The force exerted by a flowing fluid on an object in or adjacent to the flow. i. The bending of strata on either side of a fault, caused by the friction of the moving blocks along the fault surface; also, the bends or distortions so formed. CF: bull. Syn: trailer.

drag angle
 * The angle at which the leading surface of a cutting plane or point meets the surface to be cut. If less than 90 degrees, the angle is said to be negative; if over 90 degrees , it is called a positive rake or drag angle. CF: rake.

drag bit
 * a. A noncoring or full-hole boring bit that scrapes its way through strata that must not be too hard. It may be a two-, three-, or four-bladed pattern with various curves and cutaways. The drilling fluid passes down through the hollow drill stem to the cutting point. See also: roller bit.

b. Various kinds of rigid steel bits provided with fixed (as contrasted to the movable or rolling cutting points of a roller bit) and sometimes replaceable cutting points, which are rotated to drill boreholes in soft to medium-hard rock formations. See also: bit; fishtail bit; mud bit.

drag bolt
 * A coupling pin.

drag brake
 * On a revolving shovel, the brake that stops and holds the drag (digging) drum.

drag breccia
 * Fragments of rock in the brecciated zone of a fault.

drag bucket
 * A bucket widely used in sampling sea-floor rock deposits in all depths up to and exceeding 30,000 ft (9.1 km). See also: drag dredging.

drag cable
 * In a dragline or hoe, the line that pulls the bucket toward the shovel.

drag-chain conveyor
 * A type of conveyor having one or more endless chains that drag bulk materials in a trough. See also: chain conveyor; drag conveyor; portable drag conveyor. Syn: bar flight conveyor.

drag classifier
 * Inclined trough that receives ore pulp, and classifies it into settling solids and relatively fine pulp overflow. The settled material is continuously dragged up slope and out by a continuous belt, perhaps provided with transverse scrapers.

drag conveyor
 * A conveyor in which an endless chain, having wide links carrying projections or wings, is dragged through a trough into which the material to be conveyed is fed; it is used for loose material. See also: chain conveyor.

drag cut
 * a. A cut on which groups of holes are drilled at increasing heights above floor level and at increasing angles from the free face. The shots are fired to break out successive wedges of strata across the width of the face.

b. A drill-hole pattern widely used in high-speed drilling. The cut holes are inclined downward to cut a wedge along the floor, the other holes being drilled to break to the cut holes. Also called horizontal cut. c. A cut in which the cut holes are angled in the vertical plane toward a parting in order to breakout the ground along the parting. Drag cut rounds are suitable for small drifts 6 to 7 ft (1.83 to 2.13 m) wide or where shallow pulls are sufficient, but the drag cut does not find much application in large-scale drifting practice. See also: bottom cut.

drag dip
 * Local change of attitude as a result of drag near a fault.

drag dredging
 * A method in which the bucket is lowered to the sea floor and dragged over the ocean floor for some distance in order to collect samples. Dredge and trawl hauls normally can only give a rough indication of heavy or light concentrations of the minerals within an area.

drag engineer
 * See: slope engineer.

drag fold
 * A minor fold, usually one of a series, formed in an incompetent bed lying between more competent beds, produced by movement of the competent beds in opposite directions relative to one another. Drag folds may also develop beneath a thrust sheet. They are usually a centimeter to a few meters in size.

drag head
 * The underwater end of a hydraulic dredging system that comes in contact with bottom sediments and through which a dredge pump recovers a slurry of water and sediment.

dragline
 * A type of excavating equipment that casts a rope-hung bucket a considerable distance; collects the dug material by pulling the bucket toward itself on the ground with a second rope; elevates the bucket; and dumps the material on a spoil bank, in a hopper, or on a pile. See also: boom; excavator.

dragline boom
 * A crane boom used with a drag bucket.

dragline dredge
 * An excavation system involving a digging bucket, cable, and boom, which permits the recovery of sediments and rocks from trenches, canals, and pits that contain or are covered by water.

dragline engineer
 * See: slope engineer.

dragline excavator
 * A mechanical excavating appliance consisting of a steel scoop bucket that is suspended from a movable jib; after biting into the material to be excavated, it is dragged toward the machine by means of a wire rope.

dragline scraper
 * An apparatus for moving soil, gravel, or other loose material. It ordinarily consists of a scraper attached to an endless cable or belt operated by a drum or sprocket wheel, and can be drawn back and forth by the operator at the drum.

drag loader
 * See: dragman.

dragman
 * One who operates a scraper loading machine, known as a drag, to load ore into cars or chutes. Also called drag loader; drag operator.

dragon
 * S. Staff. A barrel in which water is raised from a shallow shaft.

dragonite
 * A rounded quartz pebble representing a quartz crystal that has lost its brilliancy and angular form; in gravels, once believed to be a fabulous stone obtained from the head of a flying dragon.

dragon's skin
 * Miner's term for part of a fossil tree trunk, such as Lepidodendron or Sigillaria, with a leaf-scar pattern suggesting scales.

drag operator
 * See: dragman.

drag ore
 * Crushed and broken fragments of rock or ore torn from an orebody and contained in and along a fault zone. See also: trail of a fault. Syn: drag.

drag-out loss
 * Misplacement of relatively fine material due to its adherence to a coarser fraction being settled and dragged out in mechanical classification or heavy-media separation.

drag rake
 * See: negative rake.

drags
 * Steel bars with a hook at one end and prongs at the other, which are inserted in the drawbar at the rear of the tub ascending an incline so as to prevent it running back.

drag scraper
 * a. A digging and transporting device consisting of a bottomless bucket working between a mast and an anchor.

b. A towed bottomless scraper used for land leveling. Called leveling drag scraper to distinguish from cable type.

dragshovel
 * A shovel equipped with a jack boom, a live boom, a hinged stick, and a rigidly attached bucket, that digs by pulling toward itself. Also called hoe; backhoe; pullshovel.

dragstaff
 * A pole projecting backward and downward from a vehicle, to prevent it from running backward. See also: backstay; drag.

drag-stone mill
 * A mill in which ores are ground by means of a heavy stone dragged around on a circular or annular stone bed. See also: arrastre.

drag tank
 * See: dredging sump.

drain
 * A conduit or open ditch for carrying off surplus ground or surface water. Closed drains are usually buried.

drainage
 * The manner of gravity flow of water or the process of channelization, for removal at a point remote from a mining operation. See also: drain tunnel; water hoist.

drainage basin
 * a. The area from which water is carried off by a drainage system; a watershed or a catchment area.

b. See: basin.

drainage head
 * a. The furthest or highest spot in a drainage area.

b. Difference in elevation between two points in an area to be drained.

drainage level
 * See: water level.

drainage trench
 * A channel cut alongside a mine roadway to provide for drainage and enable the proper ballasting of the rail track. The trench may be lined with precast concrete sections to a carefully laid gradient.

drainage tunnel
 * See: drain tunnel.

drained shear test
 * A shear test on a clay sample after completed consolidation under normal load, carried out in drained conditions. The strengths given by drained tests are higher than those from undrained tests.

drain hole
 * a. A borehole drilled into a water-bearing formation or mine workings through which the water can be withdrawn or drained.

b. Any hole provided in the base covering or housing on a machine through which oil or liquids can be withdrawn.

drainman
 * A laborer who regulates flow of tailings, through flumes or pipes (mixture of waste materials and water resulting from treatment of ore for recovery of valuable minerals) in back filling (filling of working places from which all ore has been mined) in such manner that water will be drawn off and the sand left for filling purposes.

drain tunnel
 * A tunnel constructed for disposing of mine water. Long tunnels have been driven in some mining districts for the purpose of passing under the lower workings of several mines and tapping the water for the entire group. Where topographic features permit, a drain tunnel--more properly called an adit--may also be driven to serve a single mine. The chief advantages of a drain tunnel lie in saving the cost of pumping and eliminating the danger of the mine being flooded through failure of the pumps. Also called drainage tunnel. CF: drainage. See also: water level.

dranyam
 * A new cutter loader devised by Maynard Davies and developed at the Central Engineering Establishment of the National Coal Board of Great Britain. A shearer drum is carried on a vertical shaft in contrast to the horizontal shaft in the Anderson shearer.

draper washer
 * Vertical-current separator (obsolete) used to separate shale from coal.

draping
 * Warping in the beds overlying a reef, as a result of differential compaction.

draft
 * a. S. Staff. The quantity of coal hoisted in a given time.

b. The pressure required to supply air to a furnace and to remove the flue gases from the furnaces. Natural draft is produced by a chimney, while artificial draft is produced by fans and is controlled by the speed of the fans, by variation in the pitch of the fan blades, or by dampers.

dravite
 * A trigonal mineral, 3[NaMg (sub 3) Al (sub 6) (OH,F) (sub 4) (BO (sub 3) ) (sub 3) Si (sub 6) O (sub 18) ] ; tourmaline group; forms series with schorl and with elbaite; in triangular or hexagonal prisms; pyroelectric and piezoelectric; in metamorphic and metasomatic lime-rich rocks; slices are used to measure transient blast pressures.

draw
 * a. The horizontal distance on the surface ahead of an underground coal face over which the rocks are influenced by subsidence. See also: angle of draw.

b. The break in strata from a coal face to the surface; the angle between this break and the vertical. c. To remove broken ore by gravity from stopes, chambers, or ore bins by aid of chutes or conveyors. d. To mine out or rob the pillars in a mine, after the rooms are worked out. e. To pull bit-bank metal toward a diamond by peening and calking when handsetting a diamond bit. f. See: pull. g. The effect of creep upon the pillars of a mine. h. To raise ore, coal, rock, etc., to the surface; to hoist. i. To transport by hand; to put; to tram. j. To allow ore to run from working places and stopes through a chute into trucks. k. To withdraw timber props from overhanging coal, so that it falls ready for collection.

drawability
 * A measure of the workability of a metal subject to a drawing process. This term is usually expressed to indicate a metal's ability to be deep-drawn.

draw a charge
 * Remove explosives.

draw bead
 * a. A bead or offset used for controlling metal flow.

b. Riblike projections on draw rings or hold-down surfaces for controlling metal flow.

drawcut
 * a. In underground blasting, cut holes that are inclined upward.

b. In rock blasting, bottom cut. c. See: drag cut.

drawer
 * a. Scot. A man or boy who takes ore or rock from the working face to the shaft, or terminus of the horse or haulage road. One who pushes trams or drives a horse underground.

b. Derb. A man who hoists ore or rock by means of a windlass, or otherwise, from a shaft. c. Putter; trammer; wagoner; a person who moves tubs either manually or with a machine.

draw firing
 * Removal of the load from a furnace for a short time, prior to the completion of burning, to equalize heating of all areas. Also called draw burning.

drawgear
 * The term includes drawbars, chains, shackles, detaching hooks, etc., used in haulage, winding, and hoisting.

draw hole
 * An aperture in a battery through which the coal or ore is drawn.

drawing
 * a. Recovering the timbers, chocks, etc., from the goaves. This work is commonly performed with the use of the dog and chain.

b. Knocking away the sprags from beneath the coal after holing. c. Raising coal through a shaft or slope. d. In hydraulic mining, throwing the water beyond the dirt to be removed and causing it to flow toward the giant. CF: goosing. e. Removing or pulling out the crown bars in a tunnel. f. The movement of tubs. g. Forming recessed parts by forcing the plastic flow of metal in dies. h. Reducing the cross section of wire or tubing by pulling it through a die. i. A misnomer for tempering. j. Continuous forming of sheet, tube or fibrous glass from molten glass.

drawing an entry
 * Removing the last of the coal from an entry.

drawing down
 * Reduction of cross section of steel by forging.

drawing lift
 * The lowest lift of a Cornish pump, or that lift in which the water rises by suction (atmospheric pressure to the point where it is forced upward by the plunger). Also called drawlift.

drawing small
 * When a winding rope, from the effects of wear and tear, has become less in diameter or in thickness from that cause, it is said to be "drawing small."

drawing timber
 * The removal of timbers and supports from abandoned or worked out mine areas. This work is highly specialized and should be attempted only by the most experienced persons. Generally, timbers are pulled by a timber puller that permits the operator to be under a safe roof while doing this work. In some cases, where so much weight is resting on the timber that it cannot be removed safely, it must be shot out by use of explosives, and the roof allowed to fall. See also: sylvester. Syn: timber drawing.

draw kiln
 * Scot. A limekiln in which the process of calcination is carried on continuously, the raw limestone and fuel being put in at the top and the lime withdrawn at the bottom.

drawman
 * See: grizzly worker.

drawn
 * The condition in which an entry or room is left after all the coal has been removed. See also: rob.

drawn clay
 * Clay that is shrunk or decreased in volume by burning.

drawn tube
 * A tube produced by drawing a tube bloom through a die.

drawpoint
 * a. A spot where gravity fed ore from a higher level is loaded into hauling units.

b. Heavy chisel cut across the face of a bit blank a short distance from a diamond to serve as a starting point for calking the metal toward and around a diamond being handset.

draw slate
 * A soft slate, shale, or rock approx. 2 in (5.08 cm) to 2 ft (0.61 m) in thickness, above the coal, and which falls with the coal or soon after the coal is removed.

draw works
 * In rotary drilling, that part of the equipment functioning as a hoist to raise or lower drill pipe and in some types, to transmit power to the rotary table. See also: hoist.

dredge
 * a. Large floating machine used in underwater excavation for developing and maintaining water depths in canals, rivers, and harbors; raising the level of lowland areas and improving drainage; constructing dams and dikes; removing overburden from submerged orebodies prior to openpit mining; or recovering subaqueous deposits having commercial value. CF: grab sampler.

b. See: dradge. c. Very fine mineral matter held in suspension in water. d. A type of bag net used for investigating the fauna of the sea bottom. e. In dry process enameling: (1) the application of dry, powdered frit to hot ware by sifting; and (2) the sieve used to apply powdered porcelain enamel frit to the ware. Also called dredging. f. Any of various machines equipped with scooping or suction devices used in deepening harbors and waterways and in underwater mining.

dredge claims
 * The bed of an unnavigable river is open to location and patent as public land, when the opposite banks thereof have not passed into private ownership. Proprietors bordering on such streams, unless restricted by the terms of their grant from the government, hold to the center of the stream, notwithstanding the running of meander lines on the banks thereof, as the true boundary of the land is the thread of the stream.

dredgemaster
 * In metal mining, a person who supervises and operates a dredge that is used to mine metal-bearing sands or gravels (gold, tin, or platinum) at the bottom of lakes, rivers, and streams. Also called dredgeman.

dredge pump
 * A heavy-duty-type centrifuged pump with chrome-carbide or manganese steel liners. In silts or rounded sand grains their life is often a matter of months, but where sharp-grained sands or large gravel sizes are being handled, casing and impeller lives may be figured in hours.

dredger
 * a. A vessel specially equipped for dredging. See also: bucket-ladder dredge; dipper dredger; grab dredger; sand-pump dredger; suction-cutter dredge.

b. Person who dredges. c. A dredging machine.

dredger excavator
 * An excavator working on the same principle as the bucket-ladder dredger but designed to work on land.

dredge sump
 * N. of Eng. A small reservoir at the bottom of a shaft, in which the water collects and deposits any sediments or debris. See also: settling pit.

dredging
 * Removing solid matter from the bottom of an area covered by water.

dredging conveyor
 * A scraper partially immersed in a vessel containing liquid used for removing any solids that may settle therein.

dredging sump
 * A tank, forming part of the water circuit, in which slurry or small coal settles and is removed continuously by means of a scraper chain or scraper buckets. Also called drag tank; sludge sump.

dredging tube
 * The large tube of a dredging machine that operates by suction.

dredging well
 * The opening through a dredging vessel in which the bucket ladders work. See also: bucket-ladder dredge.

dreelite
 * See: barite. Also spelled dreeite.

dress
 * a. To resharpen and restore to size the worn teeth on a roller or diamond bit. See also: face.

b. To restore a tool to its original shape and sharpness by forging or grinding. c. To clean ore by breaking off fragments of the gangue from the valuable mineral. See also: ore dressing. d. To shape dimension stone.

dressing
 * a. A general term for the processes of milling and concentration of ores. Syn: ore dressing.

b. The shaping of dimension stone. c. Separating rock from lumps of coal by chipping with a hammer or similar means. d. Can. Developing claims to take them out of wildcat class.

dressing a mine
 * A method of fraud carried out by a representative of the seller, by systematically mining out all the low-grade or barren spots in the vein, leaving only the high-grade spots exposed.

dribble
 * Material that adheres to the conveying medium and, being carried beyond the discharge point, drops off along the return run.

dribbling
 * In underground excavation, fall of small stone and debris from roof, warning that a heavy fall may be imminent.

dried alum
 * See: burnt alum.

drier
 * A device used for removing water from damp material by evaporation, supplemented usually with forced circulation of air.

drier man
 * In salt production, one who tends operations of rotary driers through which crushed salt is run to drive off contained moisture prior to grinding, examining the salt discharged from the driers to see that evaporation of moisture is complete.

dries
 * Seams in the rock, which are usually invisible in the freshly quarried material, but which may open up in cutting or on exposure to the weather. See also: dry.

drif
 * See: drift.

drift
 * a. An entry, generally on the slope of a hill, usually driven horizontally into a coal seam. Syn: surface. See also: adit.

b. The deviation of a borehole from its intended direction or target. CF: walk. c. A general term, used esp. in Great Britain, for all surficial, unconsolidated rock debris transported from one place and deposited in another, and distinguished from solid bedrock; e.g., specif. for glacial deposits. Any surface movement of loose incoherent material by the wind; accumulated in a mass or piled up in heaps by the action of wind or water. See also: fill. d. Apparent offset of aerial photographs with respect to the true flight line, caused by the displacement of the aircraft owing to cross winds, and by failure to orient the camera to compensate for the angle between the flight line and the direction of the aircraft's heading. The photograph edges remain parallel to the intended flight line, but the aircraft itself drifts farther and farther from that line. e. A time variation common to nearly all sensitive gravimeters, due to slow changes occurring in the springs or mountings of the instrumental systems; this variation is corrected by repeated observations at a base station and in other ways. f. A horizontal opening in or near an orebody and parallel to the course of the vein or the long dimension of the orebody. g. A passageway driven in the coal from the surface, usually above drainage, following the inclination of the bed. h. Forest of Dean. A hard shale. i. To make a drift; to drive. j. A horizontal gallery in mining and civil engineering driven from one underground working place to another and parallel to the strike of the ore. It is usually of a relatively small cross section. Larger sections are usually called tunnels. k. A heading driven obliquely through a coal seam. l. A heading in a coal mine for exploration or ventilation. m. An inclined haulage road to the surface. n. In oil well surveying, the angle from a drill hole to the vertical. See also: inclination. o. A flat piece of steel of tapering width used to remove taper shank drills and other tools from their holders. p. A tapered rod used to force mismated holes in line for riveting or bolting. Sometimes called a driftpin. q. A gradual change in a reference that is supposed to remain constant. An instrument such as a gravimeter may show drift as a result of elastic aging, long-term creep, hysteresis, or other factors. r. A general term applied to all rock material (clay, silt, sand, gravel, boulders) transported by a glacier and deposited directly by or from the ice, or by running water emanating from a glacier. Drift includes unstratified material (till) that forms moraines, and stratified deposits that form outwash plains, eskers, kames, varves, glaciofluvial sediments, etc. The term is generally applied to Pleistocene glacial deposits in areas (as large parts of North America and Europe) that no longer contain glaciers. The term drift was introduced by Murchison in 1839 for material, then called diluvium, that he regarded as having drifted in marine currents and accumulated under the sea in comparatively recent times; this material is now known to be a product of glacial activity. CF: glacial drift. s. One of the wide, slower movements of surface oceanic circulation under the influence of, and subject to diversion or reversal by, prevailing winds; e.g., the easterly drift of the North Pacific. Syn: drift current. The slight motion of ice or vessels resulting from ocean currents and wind stress. The speed of an ocean current or ice floe, usually given in nautical miles per day or in knots. Sometimes used as a short form of littoral drift. See: current. t. In South Africa, a ford in a river. The term is used in many parts of Africa to indicate a ford or a sudden dip in a road over which water may flow at times. Syn: drif. (Afrikaans)

drift and pillar
 * N. Staff. A system of working coal similar to the room and pillar system.

drift angle
 * The angular deviation of a borehole from vertical and/or its intended course. See also: deflection angle.

drift angle buildup
 * The rate of the increase in the drift angle that is generally expressed as the number of degrees increase for a specific drilled footage; e.g., 2 degrees per 100 ft (30.5 m).

driftbolt
 * a. A bolt for driving out other bolts or pins.

b. A metal rod, for securing timbers, resembling a spike but with or without point or head.

drift coal
 * See: allochthonous coal.

drift coalfields
 * Coalfields formed by forests on higher ground being carried away by floods into lakes.

drift copper
 * Native copper transported from its source by a glacier.

drift current
 * See: drift.

drift curve
 * Graph of a series of gravity values read at the same station at different times and plotted in terms of instrument reading versus time.

drift driller
 * In metal mining, one who operates a heavy, mounted, compressed-air, rock-drilling machine in driving drifts (horizontal passages running parallel to the vein opened up to facilitate mining of the ore).

drifted
 * a. A borehole, the course of which has deviated or departed from the intended direction or did not reach its intended target.

b. Inward-bulged casing that has been straightened by the use of a drift. See also: drift. c. A horizontal underground passage parallel to or along a vein or related structure.

drift epoch
 * See: glacial epoch.

drifter
 * a. An air-driven, percussive rock drill; also called leyner; liner.

b. A drill crewman, miner, or laborer who travels from place to place, only working a short period of time at each place. CF: boomer. c. A person skilled in the use of air-driven, percussive rock drills and other processes utilized in excavating horizontal underground passages or tunnels. d. An excavator of mine drifts.

drifter bar
 * See: bar; drill column.

drifter drill
 * The heaviest form of hammer drill made in various sizes depending upon the severity of the work to be done. The heaviest type weighs more than 200 lb (91 kg) and is used for holes up to 20 ft (6.1 m) in depth. Must be mounted on a column or bar.

drift frame
 * See: square set.

drift indicator
 * Various types of mechanical or photographic devices used to determine the compass bearing and inclination of the course of a borehole. CF: clinometer.

driftman
 * In bituminous coal mining, one who is engaged in driving a drift, a horizontal passageway underground following the coal vein in a mine.

driftmeter
 * An instrument for determining the inclination of a drill pipe from the vertical and the depth of measurement.

drift mine
 * a. A placer or gravel deposit worked by underground mining methods.

b. A mine that opens into a horizontal or practically level seam of coal. This type of mine is generally the easiest to open as the mine opening enters into the coal outcrop. c. One opened by a drift.

drift mining
 * a. A term applied to working alluvial deposits by underground methods of mining. The paystreak, varying from 2 to 8 ft (0.6 to 2.4 m), sometimes greater, is reached through an adit or a shallow shaft. Wheelbarrows or small cars may be used for transporting the gravel to a sluice on the surface. If relatively large, the deposit is removed in a system of regular cuts or slices taken across the paystreak, working generally in a retreating fashion from the inner limit of the gravel. Drift mining is more expensive than sluicing or hydraulicking; consequently it is used only in rich ground. See also: placer mining.

b. The working of relatively shallow coal seams by drifts from the surface. The drifts are generally inclined and may be driven in rock or in a seam. Drift mining may be viewed as intermediate between opencast coal mining and shaft or deep mining. See also: development drift; surface drift.

drift peat
 * A peat deposit associated with or embedded in glacial drift.

drift salt
 * Fluffy, flaky salt particles due to wind and wave action, which produce a mist over the surface of solar salt ponds. The mist contains minute particles of salt, which are driven to the lee shore and deposited as a scale.

drift set
 * A strong timber set in a drift that may form the anchorage for the timber sets of the stope above.

drift slicing
 * Side slicing as a method of stoping massive deposit. Alternative to top slicing.

drift stope
 * The excavation of the development drift together with the stope in overhand stoping. Employed in cases where the hanging wall is strong.

drift stoping
 * See: sublevel stoping.

drift theory
 * That theory of the origin of coal that holds that the plant matter constituting coal was washed from its original place of growth and deposited in another locality where coalification then came about. See also: allochthonous coal.

drikold
 * See: dry ice.

drill
 * a. Any cutting tool or form of apparatus using energy in any one of several forms to produce a circular hole in rock, metal, wood, or other material. See also: calyx drill; churn drill; core drill; diamond drill; rock drill; rotary drill; shot drill.

b. To make a circular hole with a drill or cutting tool.

drillability
 * a. The relative speed at which a material may be penetrated by a drill bit. High drillability denotes easy penetration at a fast rate.

b. The specific value of the drilling properties of a rock expressed in terms of the drilling rate under certain technical conditions.

drill ahead
 * a. To sink a borehole into solid or unconsolidated rock material, such as overburden or glacial till, to a considerable depth below the bottom of the casing or drivepipe.

b. To restart or resume drilling operation. c. To drill boreholes in advance of mine workings to explore for or locate old mine workings or a water-bearing formation.

drill bar
 * A drill column that is set horizontally instead of vertically in an underground workplace. See also: bar; drill column.

drill base
 * Metal or wood framework on which a drilling machine is mounted.

drill bit
 * a. One of a number of different types of detachable cutting tools used to cut circular holes in rock, wood, metal, etc. Also called drill crown in Africa and England.

b. Any device at the lower end of a drill stem, used as a cutting or boring tool in drilling a hole; the cutting edge of a drill. CF: core bit. Syn: bit; rock bit.

drill boom
 * An adjustable arm projecting from a drill carriage to carry a drill and hold it in position.

drill bort
 * See: drill diamond.

drill by
 * See: bypass. Also called drilled by and drilling by.

drill cable
 * In a strict sense, the term should only be used to designate the heavy rope or cable used as the connecting link between the drill stem and the walking beam on a churn drill. However, the term now is commonly used to signify any cable or wire rope used in hoisting drill rods, casing, and other borehole-drilling equipment used with a drill machine, such as a calyx drill, diamond drill, etc. Also called drilling line; drill line.

drill capacity
 * The lineal feet of drill rod of a specified size that a hoist on a diamond or rotary drill can lift or that the associated brake is capable of holding on a single line; also sometimes used to designate the size of a drill machine, based on the depth to which it is capable of drilling. See also: lifting capacity.

drill carriage
 * A movable platform, stage, or frame that incorporates several rock drills and usually travels on the tunnel track; used for heavy drilling work in large tunnels. See also: drill frame.

drill collar
 * A length of extra heavy wall drill rod or pipe connected to a drill string directly above the core barrel or bit, the weight of which is used to impose the major part of the load required to make the bit cut properly. A drill collar is usually of nearly the same outside diameter as the bit or core barrel on which it is used. Not to be confused with guide rod.

drill column
 * A length of steel pipe equipped with a flat cap at one end and a jackscrew on the opposite end by means of which the pipe can be wedged securely in a vertical or horizontal position across an underground opening to serve as a base on which to mount a small diamond or rock drill. Syn: drifter bar; drill bar; drill stem. See also: bar.

drill core
 * A solid, cylindrical sample of rock produced by an annular drill bit, generally rotatively driven but sometimes cut by percussive methods. Syn: core.

drill cradle
 * The metal channel on which a heavy drill is fed forward as drilling proceeds.

drill cuttings
 * See: well cuttings; cuttings; sludge.

drill diamond
 * Industrial diamond used in diamond-drill bits and reaming shells for coring, cutting, or reaming rock. Drill diamonds usually contain obvious imperfections and inclusions, although the finer grades approach toolstones in quality. Also called drill bort; drilling bort; drilling diamond; drilling. CF: toolstone.

driller
 * a. A person who has acquired enough knowledge and skill to operate and assume the responsibility of operating a drill machine. Also called drill runner; runner; tool pusher. Syn: drillman. See also: machine driller.

b. The person in charge of the rig and crew during one tour and who handles the drilling controls. c. A drilling machine. d. Can. Property being diamond drilled as compared to one undergoing underground development. e. N. of Eng. Uses an electric or pneumatic twist drill to make shotholes in the coal. Shotholes in the gateway caunches are usually put on by the stoneman.

driller's log
 * A description of the borehole based on the daily logs from the driller.

drill extractor
 * Tool for retrieving broken piece of drill from borehole.

drill feed
 * The mechanism for advancing the drill bit during boring.

drill fittings
 * Devices, parts, and pieces of equipment used downhole in drilling a borehole. Also called downhole equipment.

drill frame
 * A drill mounting often made at the mine to suit the tunnel requirements. It usually comprises two girders strapped together to form a replica of the tunnel shape but smaller in size. The structure is mounted on wheels and provision is made for clamping the drills to various parts of the frame according to the drill-hole pattern in use. It contains a central opening to allow the passage of the loading machine, cars, or conveyor.

drill gage
 * The width across the cutting bit or diameter of the drilled hole. With tungsten-carbide bits it is possible to drill long holes without the loss of gage.

drill hole
 * a. A hole in rock or coal made with an auger or a drill.

b. Technically, a circular hole drilled by forces applied percussively; loosely and commonly, the name applies to a circular hole drilled in any manner. c. Used by diamond drillers as a syn. for borehole. CF: borehole.

drill-hole counting
 * When the results of a survey indicate a possible ore deposit, test holes may be drilled and a special adaptation of a scintillation counter, called a drill-hole counter, may be lowered in a hole in an attempt to locate, outline, and assay an orebody. The drill-hole counter can distinguish between formations by their radiation intensity.

drill-hole pattern
 * The number, position, depth, and angle of the shot holes forming the complete round in the face of a tunnel or sinking pit. A good drill-hole pattern will ensure the maximum possible pull and the fragmentation for easy loading without excessive scatter of material. See also: cut holes.

drill-hole record
 * A description of the borehole based on the daily logs from the driller and the samples and the report of the geologist.

drill-hole returns
 * The circulation fluid and entrained cuttings overflowing the collar when drilling a borehole.

drill-hole survey
 * See: borehole survey.

drilling
 * a. The act or process of making a circular hole with a drill. See also: drill. CF: boring.

b. The operation of tunneling or stoping, whether with a compressed-air rock drill, a jackhammer, or a drifter. c. Use of a compressed-air rock drill to prepare rock for blasting. d. The operation of making deep holes with a drill for prospecting, exploration, or valuation.

drilling bit
 * The cutting device at the lower end of cable drilling tools or rotary drill pipe, the function of which is to accomplish the actual boring or cutting.

drilling cable
 * See: cable.

drilling column
 * The column of drill rods to the end of which the bit is attached.

drilling conditioning period
 * Time spent in circulating a higher-than-normal volume of fluid through the drilling string while slowly rotating and lowering the string from the last few feet above to the bottom of a borehole to wash away any obstructing material before resuming coring operations.

drilling jig
 * a. A device very accurately made of cast or wrought iron that becomes a guide for the drilling of holes. The work is fastened in the jig, and the drill is guided through holes drilled in the face of the jig itself. The use of a jig makes interchangeable work easily obtainable.

b. A portable drilling machine worked by hand.

drilling life
 * See: bit life.

drilling machine
 * A hand-operated, or power-driven machine for boring shot holes or boreholes, in coal, ore, mineral, or rock. See also: drifter drill; percussive drill; rotary drill; rotary-percussive drill.

drilling mud
 * A suspension, generally aqueous, used in rotary drilling and pumped down through the drill pipe to seal off porous zones and to counterbalance the pressure of oil and gas; consists of various substances in a finely divided state among which bentonite and barite are most common. Oil may be used as a base of water. CF: circulation fluid; mud-laden fluid.

drilling pattern
 * The relation of drilled holes to each other and any free faces as part of the blast design.

drilling platform
 * Auxiliary equipment for drilling at heights above head level. The drilling platform is generally assembled and dismantled for each series of drilling operations.

drilling pressure
 * See: bit load.

drilling rate
 * a. The depth of penetration achieved per unit of time with a given type of rock drill, bit diameter, air pressure, etc. See also: penetration rate.

b. The overall rate of advancement of the borehole.

drilling rig
 * A general term for the derrick, power supply, draw works, and other surface equipment necessary in rotary or cable-tool drilling. See also: rig.

drillings
 * a. See: drill diamond.

b. Incorrectly used as a syn. for cuttings. c. Sometimes designates drill diamonds ranging from 4 to 23 stones per carat in size.

drilling thrust
 * See: bit thrust.

drilling time
 * a. In rotary drilling, the time required for the bit to penetrate a specified thickness (usually 1 ft or 0.3 m) of rock. The rate is dependent on many factors.

b. The elapsed time, excluding periods when not actually drilling, required to drill a well.

drilling up
 * Preliminary digging out the clay in the taphole of a furnace. This is done usually by hand, air, or electric drill.

drilling weight
 * Also called drilled weight. See: bit load.

drill log
 * The record of the events and the type and characteristics of the formations penetrated in drilling a corehole. Syn: boring log. CF: log.

drillman
 * See: driller.

drill mounting
 * An appliance to provide a feed pressure and a support for the drilling machine usually in tunnels. Four main types of drill mountings are in use, namely, the post, the air leg, the drill frame, and the drill carriage.

drill output
 * The volume of rock (in tons) corresponding to the footage drilled per hour.

drill pattern
 * The placement of a number of boreholes in accordance to a predetermined geometric arrangement.

drill pressure
 * Also called drilling pressure. See: bit load.

drill rate
 * a. The number of feet of borehole drilled in a specified interval of time; e.g., drilling rate was 80 ft/d (24.4 m/d).

b. Price, expressed in dollars, per foot of borehole completed in accordance with terms specified in a drill contract. Syn: feed rate.

drill rig
 * A drill machine complete with all tools and accessory equipment needed to drill boreholes.

drill-rod bit
 * A noncoring bit designed to be coupled to a reaming shell threaded to couple directly on a drill rod instead of a core barrel.

drill runner
 * a. The tunnel miner who normally handles the rock drills for blasting purposes.

b. See: driller.

drill sampling
 * a. A method of sampling a deposit by means of a drill or borehole. The boreholes may be spaced at the corners of squares or triangles at distances according to the nature and extent of the deposit. See also: exploratory drilling.

b. The sampling of gravel deposits or extensive low-grade ore deposits by use of drills.

drill sharpening machines
 * Machines for sharpening detachable bits and for making shanks.

drill sludge
 * See: cuttings. Also called drilling sludge.

drill speed
 * May be used by drillers as a syn. for drill bit revolutions per minute; drill rate; feed rate; feed ratio; feed speed; rate of penetration.

drill-split longwalling
 * The act of mining tabular ores 2 to 5 m thick using a drill-split tool.

drill-split narrow-vein mining
 * The act of mining narrow veins down to 0.6 m using a drill-split tool on a carriage that is independently mobile and remote-controlled.

drill-split tool
 * A device that combines a drill and a splitter, which is a unique tool designed to apply radial and axial loads to a rock mass, into a single tool that drills and splits rock in recurring cycles.

drill steel
 * a. A round or hexagonal steel rod for boring in coal, ore, or rock. It consists of shank, shaft, and bit. It forms an important part of jackhammers and drifters.

b. Hollow steel connecting a percussion drill with the bit. c. See: stem.

drill-steel set
 * A series of integral drill-steel sizes consisting of starter and follower bits, necessary for drilling a hole to a certain depth. The length increment is usually determined by the wear of the bit and the feed length of the feeding device.

drill stem
 * a. In standard drilling, a cylindrical bar of steel or iron screwed onto the cable tool bit to give it weight.

b. In rotary drilling, a string of steel pipe screwed together and extending from the rig floor to the drill collar and bit at the bottom of the hole. The drill pipe transmits the rotating motion from the rotary table to the bit and conducts the drilling mud from the surface to the bottom of the hole. See also: drill string.

drill-stem test
 * A procedure for determining the potential productivity of an oil or gas reservoir by measuring reservoir pressures and flow capacities while the drill pipe is still in the hole, the well is still full of drilling mud, and usually the well is uncased. The tool consists of a packer to isolate the section to be tested and a chamber to collect a sample of fluid. If the formation pressure is sufficient, fluid flows into the tester. Abbrev: DST.

drill string
 * The assemblage of drill rods, core barrel and bit or drill rods, drill collars, and bit in a borehole, which is connected to and rotated by the drill machine on the surface at the collar of the borehole. Also called drill stem. See also: string.

drill thrust
 * See: bit load.

drip feeder
 * a. Oil reservoir set to discharge lubricant at steady rate in drops per minute.

b. Reagent feeder sometimes used in flotation process to meter chemicals into pulp.

dripping fault
 * A fault down which small quantities of water seep into mine workings. A dripping fault is a hazard, as mining operations may loosen or open it and cause an inrush of water.

dripstone
 * A general term for any cave deposit of calcite or other mineral formed by dripping water, including stalactites and stalagmites. See also: cave onyx; dropstone.

drivage
 * A general term for a roadway, heading, or tunnel in course of construction. It may be horizontal or inclined but not vertical.

drive
 * a. To excavate horizontally, or at an inclination, as in a drift, adit, or entry. Distinguished from sinking and raising.

b. A tunnel or level in or parallel to and near a mineralized lode or vein, as distinct from a crosscut, which only gives access normal to the lode. c. An underground passage for exploration, development, or working of an orebody. d. To advance or sink drive pipe or casing through overburden or broken rock formation by chopping, washing, or hammering with a drive hammer or by a combination of all three procedures.

drive collar
 * See: pipe drivehead.

drivehead
 * a. The driving mechanism for a conveyor. The expressions head-end drive, intermediate drive, and tail-end drive, indicate the position of the drivehead or heads.

b. A heavy iron cap or angular coupling fitted to top of pipe or casing to receive and protect the casing from the blow delivered by a drive block when casing or pipe is driven through overburden or other material. Also called drive cap; driving cap. Syn: pipe drivehead; drive collar. c. The swivel head of a diamond- or rotary-drill machine.

drivepipe
 * a. A thick-walled outside-coupled pipe, fitted at its lower end with a sharp steel shoe. It may be driven through overburden or other material by repeated pile-driverlike blows delivered to the upper end of the pipe by a heavy drive block.

b. Casing pipe driven into deep drill hole to hold back water or prevent caving. In shallow drilling of alluvials, bottom pipe of string that may be battered down. Drivehead and drive shoe are also used in this work. c. Pipe driven short distance into dumps or unconsolidated ground to obtain samples. See also: conduit.

drivepipe ring
 * a. A heavy sleevelike device attached to a drill floor to steady and guide the pipe or casing being driven.

b. A device for holding the drivepipe while being pulled from well.

drive sample
 * A dry sample of soft rock material, such as clay, soil, sand, etc., obtained by forcing, without rotation, a short, tubular device into the formation being sampled by hydraulic pressure or the piledriver action of a drive hammer.

drive sampler
 * A short tubelike device designed to be forced, without rotation, into soft rock or rock material, such as clay, sand, or gravel, by hydraulic pressure or the piledriver action of a drive hammer to procure samples of material in as nearly an undisturbed state as possible. CF: piston sampler. See also: thick-wall sampler.

drive sampling
 * The act or process of obtaining dry samples of soft rock material by forcing, without rotation, a tubular device into the material being sampled by pressure generated hydraulically, mechanically, or by the piledriver action of a drive hammer.

drive shaft
 * a. Main driving shaft on which the drive and conveyor sprocket wheels or pulleys are mounted. This shaft is connected to the drive unit through a coupling, sprocket wheel, gear, or other form of mechanical power transmission.

b. A shaft used to support the end of a conveyor screw in a trough end and as a driving connection between a conveyor screw and the power transmitting medium.

drive unit
 * The mechanism that imparts the reciprocating motion to a shaker conveyor trough line. The term is frequently shortened to drive, such as shaker drive, uphill drive, etc.

drive wedge
 * A metal wedge, driven into a wooden or soft-metal base plug in a borehole, that acts as a fixed point on which and by means of which a deflection wedge may be set and oriented.

driving
 * a. Extending excavations horizontally or near the horizontal plane. CF: sinking; raising.

b. The making of a tunnel or level (a drive) in a mineralized lode or vein, as distinct from making one in country rock (crosscutting). c. Breaking down coal with wedges and hammers. d. A long narrow underground excavation or heading. e. Eng. In the Bristol coalfield, a heading driven through rock.

driving cap
 * Steel cap placed above line of casing pipes of drill hole to protect threaded top of pipe while driving them deeper. Driving shoe gives protection to the bottom pipe of line.

driving head
 * The driving mechanism of a belt conveyor. It consists of an electric motor or compressed-air turbine connected through a train of reduction gearing to the drum or drums. Motion is imparted to the belt by the frictional grip between it and the drums.

driving on line
 * The keeping of a heading or breast accurately on a given course by means of a compass or transit. Also, called driving on sights.