Appendix:Dictionary of Mining, Mineral, and Related Terms/J/1

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See: essonite; hyacinth; zircon.


a. A name for zinc ore; blackjack. See: sphalerite.

b. Cannel coal interstratified with shale. c. Coaly shale, commonly canneloid. d. To drill a rock by hand, using a 4-lb (1.8-kg) hammer in one hand and a steel drill in the other ("single jacking"). "Double jacking" is to use a two-handed (sledge) hammer with the steel drill held by another worker. e. A portable device used for exerting great pressure or for lifting a heavy body through a small distance. Syn: anchor jack.

jack boom

a. A boom that supports sheaves between the hoist drum and the main boom in a pull shovel or a dredge.

b. A boom whose function is to support sheaves that carry lines to a working boom.

jack catch

Safety catch in the rail track to stop tubs running back on inclines.

jack engine

Eng. A donkey engine; a small engine employed in sinking a shallow shaft.


An outer casing or cover constructed around a cylinder or pipe, the annular space being filled with a fluid for either cooling, heating, or maintaining the cylinder contents at constant temperature; e.g., the water jackets of an internal combustion engine.

jacket set

a. Set of timbers used in a shaft outside the regular shaft set, as extra protection in heavy ground.

b. Set like the larger shaft set with dividers omitted, except that the wall and end plates are broken at all joints to facilitate renewing. Used in heavy ground to protect the regular shaft timbers. The jacket set is placed outside the regular timbers, separated from them by short blocks, and is blocked and wedged against the rock.


A percussive type of automatically rotated rock drill that is worked by compressed air. It is light enough to be used without a tripod and to be hand held.


See: delivery drift.

jackhead pit

a. A small pit without hoisting appliances, frequently serving as a ventilation shaft.

b. A small shaft sunk within a mine. A winze.

jackhead pump

A subordinate pump in the bottom of a shaft, worked by an attachment to the main pump rod.

jackhead set

Newc. The set of pumps in the jackhead staple.

jackhead staple

Eng. A small mine for the supply of coal for the boilers.

jack hole

Eng. In coal mining, a bolthole. See also: cut-through.

jacking pressure

The amount of pressure exerted by a jack to force a cone penetrometer into a soil being tested.

jacking up

The raising up of masses of machinery and heavy structures by means of jacks.


The collapse of a drill tripod or derrick.

jackknife rig

A truck-mounted diamond or small rotary drill equipped with a hinged derrick.


A collapsing of square-set timbers by wall pressure or through poor placement.


a. Light supporting bar for use with a jackhammer.

b. An outrigger post.


A hollow iron pipe large enough to slip over the end of the front jack of a cutting machine to make it hold more firmly against the coal.

jack pit

N. of Eng. A shallow shaft in a mine communicating with an overcast. See also: jackshaft; overcast. Syn: jacky pit.

jack post

This timber is used where the coal seam is separated by a rock band and one bench is loaded out before the other. If the top bench is worked off first, the jack posts are set between the bottom bench of the coal and the roof. If the bottom bench is cleaned up first, the jack posts are set between the bottom and the top bench. At least two jack posts should be used and as many more as is necessary to keep the top bench of coal or the roof from coming down while the coal is being loaded out.


A windlass worked by hand.


a. A jack in which a screw is used for lifting or exerting pressure; also,#WORD �48� �56� screwjack �13126� �13127� the helical-screw part of a jackscrew. Syn: screwjack.

b. A heavy screw set in the base or frame of a drill machine for the purpose of leveling the drill.

jack setter

A miner who assists in the operation of an auger-type underground mining machine; duties include seeing that the roof of the mine at or near the machine is in a safe condition. See also: machine helper.


An intermediate driving shaft. See also: jack pit.

jacky pit

See: jack pit.


An isometric mineral, 8[MnFe (sub 2) O (sub 4) ] ; spinel group; occurs with manganese ores.

Jacobs process

A method in which bauxite is fused in an electric furnace to form a synthetic corundum.

Jacob staff

A straight rod or staff pointed and shod with iron at the bottom for insertion in the ground, having a socket joint at the top, and used instead of a tripod for supporting a compass.

Jacquet's method

Use of electrolytic polishing to complete the finish on metal surfaces. After mechanical polishing they are made the anodes in a suitable electrolyte.


An ultramafic plutonic rock that is part of the ijolite series; composed chiefly of titanaugite and magnetite, with a smaller amount of nepheline; a nepheline-bearing clinopyroxenite. Its name, given by Derby in 1891, is derived from Jacupiranga, Brazil.


A term used in Brazil for disaggregated, powdery itabirite, and for variegated thin-bedded, high-grade hematite iron ores associated with and often forming the matrix of gold ore. Etymol. from its resemblance to the colors of the plumage of Pipile jacutinga, a Brazilian bird. CF: itabirite.


a. Som. A long and deep holing, cutting, or jud, made for the purpose of detaching large blocks of stone from their natural beds.

b. Prov. Eng. To undercut (coal or rock).


A microcrystalline gem variety of jadeite or nephrite (actinolite) with a toughness (resistance to breakage) exceeded only by that of carbonado diamond; ranges from nearly white to emerald-green, the latter being the most valuable; finest quality is reported to come from northern Burma (Myanmar) and the Yunnan Province of south China. The emerald-green color is attributed to jadeite and to trace amounts of chromium. There are many imitations of jade, including green-dyed onyx (Mexican jade), aventurine quartz containing fuchsite mica (Indian jade), vesuvianite (California jade), green hydrogrossular from South Africa, green organic or inorganic dyes or substitutes inserted under white jade, glass, dyed quartz, and bowenite or williamsite varieties of serpentine. "Jade cat's-eye" is a contradiction in terms. See: jadeite; nephrite; toughness.


A monoclinic mineral, 4[NaAlSi (sub 2) O (sub 6) ] ; pyroxene group; apple green to emerald green, white, lavender, tomato red, or brown; tough; associated with albite from high-pressure, low-temperature metamorphosed plagioclase; an ornamental stone called "jade" (along with nephrite).


A metamorphic rock consisting principally of jadeite, commonly associated with small amounts of feldspar or feldspathoids. It is probably derived from an alkali-rich igneous rock by high-pressure metamorphism.


A deep-green chromiferous syenite cut as a gemstone and resembling jade in appearance. Obsolete.

jag bolt

An anchor bolt with a barbed flaring shank, which resists retraction when leaded into stone or set in concrete. Also called hacked bolt; rag bolt.


A bluish-white diamond of modern cut.

jagging board

An inclined board on which ore slimes are washed, as in a buddle.


A trigonal mineral, Pb (sub 3) FeSi (sub 4) O (sub 12) (Cl,OH) ; in yellow-green micaceous plates associated with another lead-iron silicate (melanotekite) in iron ore at Laangban, Sweden.


Som. A small tub or box in which water is carried in a mine.


A tetragonal mineral, Ag (sub 3) CuS (sub 2) ; forms intergrowths with argentite in the Black Hawk District, Grant County, NM.


The blocking of a core barrel or core bit with core, sometimes deliberately.


a. A vein or bed of earth or stone, that prevents miners from following a vein of ore; a large block.

b. A projecting columnar part (as of a masonry wall) or mass (as of ore). c. A vertical structural member forming the side of an opening in a furnace wall. d. A type of brick shape intended for use in the sides of wall openings. e. Sidewall of port of furnace superstructure carrying port crown load.

jamb cutter

In the coke products industry, a laborer who chips carbon and mud from the edges of coke-oven doors with a steel bar prior to the discharge of the coke.

jamb stick

See: gim peg.

jamb wall

See: breast wall.

James jig

Movable sieve box supported on a rubber diaphragm and jigged mechanically up and down.


A monoclinic mineral, 2[Pb (sub 4) FeSb (sub 6) S (sub 14) ] ; metallic gray to black; in acicular crystals or capillary forms of featherlike appearance, thus the term "feather ore;" in low- to medium-temperature veins with other lead sulfosalts, galena, and carbonates. Syn: wolfsbergite; feather ore.

James table

Shaking table used in concentration of ground ores by gravity.

jam out

S. Staff. To cut or knock away the coal between holes.

jam riveter

A riveting hammer provided with an air-operated telescopic casing to hold the hammer against the work.


a. An appliance to permit relative movement between the rope and rods in a cable drill. It reduces shocks and the risk of rod or chisel breakages. See also: free-falling device.

b. To loosen or free stuck drill-stem equipment or tools by impacts delivered by quick, sharp, upward-traveling blows delivered by a drive hammer or jars.

jar collar

A swell coupling, attached to the upper exposed end of a drill rod or casing string, to act as an anvil against which the impact blows of a drive hammer are delivered and transmitted to the rod or casing string; also, sometimes used as a syn. for drive hammer. Also called drive collar; jar head. Syn: bell jar.


A colorless, yellow, or smoky gem variety of zircon.


A monoclinic mineral, NaSr (sub 3) Al (sub 3) (F,OH) (sub 16) ; in brownish crystals and spherulites at Ivigtut, Greenland.

jar mill

a. A small batch mill of ceramic material used in ore-testing laboratories in investigation of grinding problems.

b. Any of the stoneware-lined pebble mills used in milling enamels on a small scale. c. See: ball mill.

Jarno taper

This taper of 0.6 in/ft (4.2 cm/m) is used by a number of manufacturers for taper pins, sockets, and shanks used on machine tools.


A trigonal mineral, KFe (sub 3) (SO (sub 4) ) (sub 2) (OH) (sub 6) ; alunite group; amber yellow to dark brown; forms druses of minute crystals, crusts, and coatings; may be fibrous or fine-grained and massive; associated with volcanic rocks; thought to form under solfataric conditions at elevated temperatures and pressures; in some places with alunite; at many localities in the Western United States, Bolivia, Europe, and Russia. See also: cuprojarosite; kirovite.


See: agate jasper.


A red variety of chalcedony. See also: chert; chalcedony. Syn: jasperite.

jasper bar

See: jaspilite.


Banded jasper of varying colors.


See: jasper.


The conversion or alteration of igneous or sedimentary rocks into banded rocks like jaspilite by metasomatic introduction of iron oxides and cryptocrystalline silica. See also: jaspilite.


a. A dense, usually gray, chertlike siliceous rock, in which chalcedony or cryptocrystalline quartz has replaced the carbonate minerals of limestone or dolomite; a silicified limestone. It typically develops as the gangue of metasomatic sulfide deposits of the lead-zinc type, such as those of Missouri, Oklahoma, and Kansas.

b. Resembling jasper.

jasper opal

An almost opaque common opal; commonly yellow-brown, reddish brown to red owing to iron oxides; resembles opal but has the luster of common opal. Also called jaspopal.


Resembling or containing jasper; jaspery.


Interbedded jasper and iron oxides. CF: iron formation. Syn: jasper bar. See also: jasperization.


An opaque onyx, part or all of whose bands consist of jasper.


a. In a crusher, one of a pair of nearly flat or ribbed faces separated by a wedge-shaped opening.

b. One or a set of two or more serrate-faced members between which an object may be grasped and held firmly, as in a vise, drill chuck, foot clamp, or pipe wrench. c. In a clutch, one of a pair of toothed rings, the teeth of which face each other.

jaw breaker

See: jaw crusher.

jaw crusher

a. A primary crusher designed to reduce large rocks or ores to sizes capable of being handled by any of the secondary crushers.

b. A crushing machine consisting of a moving jaw, hinged at one end, which swings toward and away from a stationary jaw in a regular oscillatory cycle. c. A machine for reducing the size of materials by impact or crushing between a fixed plate and an oscillating plate, or between two oscillating plates, forming a tapered jaw. Syn: jaw breaker.

jedding ax

A stonecutter's ax with a flat face and a pointed peen.


A kind of vermiculite from West Chester, Chester County, PA.


A variety of monoclinic pyroxene, commonly augite or diopside, containing manganese and zinc; forms large, coarse crystals having rounded edges and uneven faces; at Franklin, NJ.

Jeffrey crusher

Crusher used to break softish materials; e.g., limestone and coal. See also: swing-hammer crusher. Syn: whizzer mill.

Jeffrey diaphragm jig

A plunger-type jig with the plunger beneath the screen. May be either single or multiple compartments. Its distinguishing features are (1) the stroke is produced with a cam operated by a lever and rocker-arm mechanism, (2) the weight of the column of water above the plunger is balanced by means of compressed air, (3) automatic operation is obtained by means of a submerged float that measures the specific gravity of the mass of coal, refuse, and water at the peak of the pulsion stroke, (4) refuse is withdrawn through a star gate extending the full width of the overflow lip, and (5) the slope of the screen plate is readily adjustable by means of heavy screws at the feed end. It is widely used on bituminous coal on sizes ranging up to a maximum of 6 in (15 cm).

Jeffrey molveyor

An arrangement to keep a continuous miner in full operation at all times. It consists of a series of short conveyors, each mounted on driven wheels and coupled into a train to run alongside the heading or room conveyor.

Jeffrey-Robinson cone

A cone for coal washing; similar to the Callow and Caldecott cones. See also: cone classifier.

Jeffrey single-roll crusher

A simple type of crusher for coal, with a drum to which are bolted toothed segments designed to grip the coal, forcing it down into the crushing opening.

Jeffrey swing-hammer crusher

A crusher enclosed in an iron casing in which a revolving shaft carries swinging arms having a free arc movement of 120 degrees . The rotation of the driving shaft causes the arms to swing out and strike the coal, ore, or other material, which, when sufficiently fine, passes through the grated bottom.

Jeffrey-Traylor vibrating feeder

A feed chute vibrated electromagnetically in a direction oblique to its surface. Rate of movement of material depends on amplitude and frequency of vibration.

Jeffrey-Traylor vibrating screen

An electric vibrating screen operated by action on an oscillating armature and a stationary coil.


See: carbohumin; vegetable jelly.


a. A drivage at right angles to the main cleat.

b. Eng. A road driven bordways in a pillar of coal. A jud driven bordways along a pillar of coal with goaf or an old bord on one side is called a "loose end jenkin." c. N. of Eng. A variation of "junking."


A ferroan variety of antigorite.

Jeppe's tables

A series of tables esp. compiled for mining work that includes tables of density, vapor pressure, and absolute humidity.

Jeppestown shales

S. Afr. Part of the Jeppestown Series forming the footwall of the Main Reef on the Central and East Rand.

jerking table

See: shaking table.

jerry man

An employee in a mine whose duty it is to clean up falls or refuse, or to make a miner's working place safe. See also: wasteman.

Jersey fire clay brick

A highly siliceous clay brick, semisilica brick.


Beds of decomposed gypsum.


a. A hard black variety of cannel coal or brown coal, compact in texture, having a rough fracture and dull luster that takes a good polish and is thus used in the jewelry trade. Syn: black amber. See also: jet shale.

b. A sudden and forceful rush or gush of fluid through a narrow or restricted opening; e.g., a stream of water or air used to flush cuttings from a borehole. c. A black variety of marble. d. Jet piercing, a thermal method of drilling large-diameter blast holes in hard cherty iron formation (taconite); formerly used mainly on the Mesabi Range in Minnesota, but also on the Marquette Range in Michigan. The rotating drill head is fed a mixture of kerosene and oxygen, ignited to direct a high-temperature flame against the rock, causing the rock to spall into fine particles by thermal expansion. Method has been almost totally replaced by rotary drills using tricone bits. See also: jet hole.

jetair flotation machine

A multiple-cell machine of the mechanical agitation type.

jet-assisted cutting

a. Cutting rock by the very high force of a water jet against the ore so that the material could be processed for mineral recovery.

b. Penetration of high-pressure water into material cracks such that the cracks between the grains are propagated and cutting occurs. See also: hydraulic mining.

jet coal

See: cannel coal.

jet corer

Consists of a length of pipe that is lowered from a vessel to obtain samples. High-velocity water is pumped through the pipe, and the jetting action of this water issuing from the lower end of the pipe very effectively cuts a hole in the unconsolidated overburden sediments. Once at bedrock, the pipe is rammed into the rock with sufficient force to obtain a plug several inches in length.

jet drilling

Piercing of rock strata by use of high-temperature flame to fuse the rock, together with jets of water to cause decrepitation and to flush the fragments out.

jet grinding mill

Enclosed chamber of relatively small cross section in which gas, at substantially high atmospheric pressures, is circulated at high speed, 400 to 700 ft/s (120 to 210 m/s).

jet hole

a. A borehole drilled by use of a directed, forceful stream of fluid or air. See also: jet.

b. A small hole in a nozzle. See also: jet.

jet hydraulic

Stream of water used in alluvial mining.

jet impact mill

See: fluid energy mill.


A powder loader for loading horizontal drill holes with a diameter of more than 2 in (5.1 cm). It is intended for AN-prills and oil, and is also employed to blow sand into the holes for stemming.

jet mill

Differs from other mills in that the material is not ground against a hard surface. Instead, a gaseous medium is introduced. The gas may convey the feed material at high velocity in opposing streams or it may move the material around the periphery of the grinding and classifying chamber. The high turbulence causes the particles and feed material to collide and grind upon themselves.

jet mixer

An apparatus that utilizes the mixing action of a water stream jetted into dry drill-mud ingredients to form a mud-laden fluid. CF: atomizer.

jetonized wood

A name given to vitrain lamellae in coal. Synonymous with vitrain.

jet piercing

The use of high-velocity jet flames to drill holes in hard rocks, as taconite, and to cut channels in granite quarries. It involves combustion of oxygen and a fuel oil fed under pressure through a nozzle to produce a jet flame generating a temperature above 2,600 degrees C. A stream of water joins the flame, and the combined effect is a thermodynamic spalling and disintegration of the rock into fragments that are blown from the hole or cut. Syn: thermic drilling.

jet-piercing drill

See: fusion-piercing drill.

jet pump

Consists of a centrifugal pump and motor at the ground surface and a jet down in the well below the water level, discharging at high velocity through a contracted section into the lift pipe. The centrifugal pump has two discharge pipes; one leads down to the jet, the other carries the water into the distribution system or into a storage tank. Syn: jet impact mill.

jet rock

a. A coallike shale containing jet.

b. See: jet shale.

jet shale

Bituminous shale containing jet. See also: jet. Syn: jet rock.


A term for black tourmaline (schorl) in New South Wales, Australia.


Corn. The horizontal rods or poles connecting the water wheel and the pumps.


The process of sinking a borehole, or of flushing cuttings or loosely consolidated materials from a borehole, by using a directed, forceful stream (jet) of drilling mud, air, or water.

jetting drill

A percussive drill for prospecting through superficial deposits. The drill is given a short stroke, 10 to 20 cm, and rotated by hand. Water is pumped down through the hollow steel rods and escapes through openings in the chopping bit. Casing is used, and the drilling rate is from 6 to 12 m per shift.

jetting pump

A water pump that develops very high discharge pressure.


a. An engineering structure (such as a breakwater, groin, seawall, or small pier) extending out from the shore into a body of water, designed to direct and confine the current or tide, to protect a harbor, or to prevent shoaling of a navigable passage by littoral materials. Jetties are often built in pairs on either side of a harbor entrance or at the mouth of a river.

b. A British term for a landing wharf or pier used as a berthing place for vessels.

jeweler's shop

a. Corn. Miner's expression for a rich section of ore.

b. Aust. A very rich patch of gold in either a reef or an alluvial formation.

jews' tin

Ancient slabs of tin found in Cornwall, England; so called from the belief that they were made by Jewish merchants and miners from Asia Minor before the present era of mining.


The lifting arm of a crane or derrick having a pulley at its outer end over which the hoisting rope passes. See also: front-end equipment.


The operation of gradually working the jib of a shortwall coal cutter into the cutting position in the coal seam. Jibbing-in is the first operation before starting the cutting run across the face. Syn: sumping-in.

jib crane

A crane having a swinging boom or jib.

jib end

In conveyor systems, the delivery end when a jib is fitted to deliver the load in advance of and remote from the drive.

jib holeman

A person whose work is to make recesses for the cutting disk at the end of coal-cutting machine faces.

jib in

The process of starting a cut by swinging the jib of the coal cutter (while the chain is cutting) from the front of the face to the full cutting position. See: sump.


a. A device that separates coal or ore from foreign matter, by means of their difference in specific gravity, in a pulsating water medium. Also spelled gig. See also: Baum jig; Bendelari jig; conset jig; Denver jig; Harz jig; hutch; jigger; jig washer; Pan-American jig; stripping a jig.

b. A link or coupling connecting mine wagons.

jig bed

The agent used in a jig that consists of the heavy fractions in the coal that behave in some respects like a dense fluid. The pulsation of the water or the motion of the screen keeps the bed open or in suspension during part of the cycle so that heavy minerals entering the jig can settle into the bed. Lighter materials cannot penetrate the jig bed and therefore are forced to remain in the upper part of the jig and eventually discharge over the top. Other agents in use are lead shot, iron punchings, iron shot, pyrite, and magnetite.

jig brow

Self-acting inclined track used to lower filled coal tubs and raise empty ones.

jig bushing

Hardened-steel bushing inserted in the face of a jig to serve as a guide for drills.

jig chain

S. Staff. A chain hooked to the back of a skip and running around a post to prevent its too rapid descent on an inclined plane. CF: snub.

jig dips

N. Staff. See: crossgate.


a. See: pan conveyor; shaker conveyor; jigging conveyor.

b. Scot. An apparatus for attaching hutches to a haulage rope. c. A mechanism that operates with quick up-and-down motion; a jolting device. See also: jig. d. A machine for dressing small ore in which a sieve is dipped or moved about under water. e. Leic. A coupling hook used between coal cars. f. Person that concentrates ore by jigging.

jigger work

Eng. Dressed or partly dressed ore obtained from jigging.


a. The separation of the heavy fractions of an ore from the light fractions by means of a jig.

b. Up-and-down motion of a mass of particles in water by means of pulsion. c. See: skimping.

jigging conveyor

A series of steel troughs suspended from roof of stope or laid on rollers on its floor and given reciprocating motion mechanically to move mineral. Syn: jigger; pan conveyor.

jigging machine

A machine to jig ore. See also: jig.

jigging screen

A screen or pair of screens to which a combined horizontal and vertical motion is imparted, normally by a crankshaft and connecting rod, the screen decks being horizontal or inclined at a small angle. See also: shaking screen.

jiggling in

A technique for transferring a surface survey down a mine shaft in such a manner as to tie it in to an underground mine survey. See also: coplaning.

jig haulage

See: gravity haulage.

jig indicator

An apparatus resembling a steam engine indicator; used for drawing curved lines illustrating the action of jigs in ore beneficiation.

jig pin

A pin used to prevent the turning of the turn beams.

jig washer

A coal or mineral washer for relatively coarse material. The broken ore, supported on a screen, is pulsed vertically in water; the heavy (valuable) portion passes through the screen into a conical receptacle (hutch), and the gangue goes over the side. In coal washing, the heavy (worthless) shale passes downwards, and the lighter coal remains on top. See also: plunger jig washer; jig.


An orthorhombic mineral, Mn (sub 3) B (sub 2) O (sub 6) ; the manganese analog of kotoite; with other manganese minerals at the Kaso Mine, Kanuma, Tochigi Prefecture, Japan.

Jim Crow

A portable hand-operated appliance for bending or curving rails. It incorporates a strong buttress screw thread.

jinny road

Underground gravity plane.


Leic. A short heading along which empties, horses, or workers travel.


A monoclinic mineral, Ba (sub 2) NaCe (sub 2) Fe(Ti,Nb) (sub 2) Si (sub 8) O (sub 26) (OH,F).H (sub 2) O ; dimorphous with orthojoaquinite; forms minute honey-colored crystals; with benitoite and neptunite in San Benito County, CA.


Scot. An iron rod, usually pronged, attached to the rear end of a train of hutches or cars being drawn up an incline; used to stop their descent in the event of the rope breaking.


a. Aust. A Y-shaped grip placed in sockets at the end of a skip. The endless rope rests on this when used above the skip.

b. Mid. A self-acting apparatus on the front of a car, for releasing it from the hauling rope at a certain point.


a. A joint of trusses or sets of timber for receiving pressure at right angles or nearly so.

b. Notches cut in round timbers set above other round pieces in underground timbering. c. An offset in a flat plane consisting of two parallel bends in opposite directions by the same angle. d. A slight step-shaped offset formed into a flat piece of metal (as for providing a flange).


An orthorhombic mineral, CaAlB (sub 3) O (sub 7) ; forms transparent grains and lamellar masses; fluoresces an intense blue owing to traces of rare-earth elements; in nepheline dikes, cutting sandstone in the Johachido District, Kenkyohokuco Prefecture, Korea.


A triclinic mineral, [Cu(UO (sub 2) ) (sub 2) (SO (sub 4) ) (sub 2) (OH) (sub 2) .8H (sub 2) O] ; radioactive; forms soft, bitter-tasting crystals that are polysynthetically twinned in two directions; in druses and reniform masses; at Joachimsthal, Czech Republic, and Gilpin County, CO; associated with gypsum.


A monoclinic mineral, 4[CaMnSi (sub 2) O (sub 6) ] ; pyroxene group; forms series with diopside and hedenbergite; shows clove-brown to grayish-green columnar, radiating, and spherulitic aggregates of fibers and prisms with black tarnish; in metasomatized limestones with manganese ore. Occurs at Puebla and Hildago, Mexico; Lane County, OR; Franklin, NJ; and Schio, Venetia, Italy.

Johannsen number

A number, composed of three or four digits, that defines the position of an igneous rock in Johannsen's classification. The first digit represents the class, the second the order, and the third and fourth the family. CF: Johannsen's classification.

Johannsen's classification

A quantitative mineralogic classification of igneous rocks developed by the petrographer Albert Johannsen (1939). CF: Johannsen number.

John Odges

See: gun.

Johnson concentrator

A cylindrical shell lined with grooved rubber set parallel to its axis, which is inclined, peripheral riffles thus being formed. Used to arrest heavy particles such as metallic gold as auriferous pulp flows gently through while the cylinder revolves slowly and the arrested material rises and drops on to a separate discharge launder.

Johnston vanner

Modified form of Frue vanner.


See: rinkite.


a. A divisional plane or surface that divides a rock and along which there has been no visible movement parallel to the plane or surface.

b. A standard length of drill rod, casing, or pipe equipped with threaded ends by which two or more pieces may be coupled together; also, two or more standard lengths of drill rods or pipe coupled together and handled as a single piece in round trips. c. A fracture or parting that cuts through and abruptly interrupts the physical continuity of a rock mass. Not to be confused with bedding or cleavage. d. A line of cleavage in a coal seam. Syn: heading seam. See also: joint plane.

joint box

A cast iron box surrounding an electric cable joint, often filled with insulation after the joint between cables has been made.


a. In quarrying, the process of cutting to specified sizes and shapes, with smooth unchipped edges.

b. The condition or presence of joints in a body of rock.

jointing sleeves

Insulating thimbles placed over the connected ends of detonator leads coupled in large rounds of shots, and also over the connections between the detonator leads and the shot-firing cable.

joint line

A visible line on imperfect glassware reproducing the line between separate parts of the mold in which the glass was made. Also called parting line; match mark; miter seam; mold mark; mold seam. Syn: seam.

joint plane

A plane along a joint fracture or parting. Not to be confused with bedding and/or cleavage. See also: joint.

joint rose

A rose diagram that shows the azimuth and intensity of jointing in an area.


Natural cracks or fractures in rocks. They tend to occur in more or less parallel systems, and when quarry walls are maintained parallel and at right angles to them, they may be utilized as natural partings in the process of block removal.

joint set

A group of more or less parallel joints.

joint system

Consists of two or more joint sets or any group of joints with a characteristic pattern, such as a radiating pattern and a concentric pattern.


Full of joints; specif. in mining, full of minute cracks or crevices, as rock.

Jolly balance

a. A spring balance used to measure specific gravity of mineral specimens by weighing a specimen both in the air and immersed in a liquid of known density.

b. A spiral-spring balance with two specimen pans, one for measuring weight in air and one for weight in water, used to determine specific gravity. CF: Westphal balance.

Jominy test

A hardenability test in which a standard test piece, 4 in (10.2 cm) long and 1 in (2.54 cm) in diameter, is heated to a predetermined temperature, rapidly transferred to a jig fixture, and quenched, under standard conditions, by a jet of water impinging at one end. When the specimen is cool, determinations of hardness are made along it from the quenched end. The diagram relating hardness to distance from the quenched end of the specimen is known as a hardenability curve.

Jones riffle

An apparatus used for cutting the size of a sample. It consists of a hopper above a series of open-bottom pockets, usually 1/2 in or 3/4 in (1.27 cm or 1.91 cm) wide, which are so constructed as to discharge alternately, first into a pan to the right, and then into another pan to the left. Each time the sample is passed through the riffle, it is divided into two equal parts; the next pass of one of those parts will give a quarter of the original sample, and so on, until the sample is reduced to the desired weight.

Jones splitter

A device used to reduce the volume of a sample consisting of a belled, rectangular container, the bottom of which is fitted with a series of narrow slots or alternating chutes designed to cast material in equal quantities to opposite sides of the device. Also called sample splitter. CF: riffle.

Joosten process

Method of soil consolidation used in tunneling through sands and gravels. Solutions of calcium chloride and sodium silicate are forced into the ground, where they mingle and produce a watertight gel.

Joplin jig

A device used for jigging the shaker products of the diamond washer. The products are fed to the jigs, one at a time, and jigged, with frequent stoppages for scraping off the top layer of tailings; more sand is added, and the process is repeated until a product is obtained that consists entirely of concentrates.


A monoclinic mineral, Pb (sub 14) (As,Sb) (sub 6) S (sub 23) ; pseudohexagonal; forms a series with geochronite in which antimony increases relative to arsenic.


A scoop-shaped bamboo basket used in Japan for carrying auriferous gravel.


A trigonal mineral, Bi (sub 4) TeS (sub 2) ; sp gr, 7.9; (super ) at San Jose, Minas Gerais, Brazil. A related mineral, jose#1.ite-B, contains more tellurium and less sulfur.


See: hartite.


A gray, nickeliferous iron, Fe (sub 2) Ni (sub 5) or FeNi (sub 3) . Massive, granular, and forms the metallic portion of rolled pebbles. From Josephine County, OR. Syn: native nickel-iron.


a. The absolute meter-kilogram-second (mks) unit of work or energy that equals 10 (super 7) erg or approx. 0.7377 or 0.2390 g (caloric); the standard in the United States.

b. The gram-degree centigrade thermal unit; the small calorie.

Joule's law

The rate at which heat is produced by a steady current in any part of an electric circuit is jointly proportional to the resistance and to the square of the current.

jouph holes

Derb. Hollows in a vein.

jourado diamond

A colorless synthetic spinel used as a simulated diamond.


That part of a rotating shaft resting in a bearing.


a. Welsh term for train of mine cars moved mechanically. Also called gang; set; rake.

b. A cycle of work done in glass manufacturing in converting a quantity of material into glass or glass products.

Joy double-ended shearer

A cutter loader for continuous mining on a longwall face. It consists of two cutting heads fixed at each end of a continuous-track-mounted chassis. The heads are pivoted and controlled hydraulically for vertical movement. Each head comprises two bores and a frame or loop cutter that trims the bottom, face, and top. A cross conveyor delivers the coal to the adjacent face conveyor. The machine cuts a web of 5 ft (1.5 m) in seams from 37-1/2 in (95 cm) to 5 ft high. With an overall length of 18 ft (5.5 m), it weighs 15 st (13.6 t).

Joy extensible conveyor

A belt conveyor to serve between a loader or continuous miner and the main transport. It consists of two main units, a head and a tail section, each mounted on crawler tracks and independently driven. In operation, the tail unit (i.e., the receiving end) moves forward with the loading machine, and belting is automatically released from a loop takeup. Fifty feet (15 m) of advance is possible before additional belting has to be inserted into the conveyor run. Capacity equals 280 st/h (254 t/h) with a 30-in (76-cm) belt.

Joy extensible steel band

An arrangement to provide a link between a continuous miner and the main transport. The equipment is hydraulically driven, and the steel band is coiled on the drivehead.

Joy loader

Loading machine for coal or ore that uses mechanical arms to gather mineral onto an apron pressed into the severed material. A built-in conveyor then lifts it into tubs or onto a conveyor.

Joy microdyne

A wet-type dust collector for use at the return end of tunnels or hard headings. It may be either 6,000 ft (super 3) /min or 12,000 ft (super 3) /min (2.8 m (super 3) /s or 5.7 m (super 3) /s) in capacity. It wets and traps dust as it passes through the appliance, and releases it in the form of a slurry, which is removed by a pump. The microdyne is bolted to the outby end of the exhaust pipe, and the auxiliary fan is bolted to the outby end of the dust collector.

Joy transloader

A rubber-tired, self-propelled loading, transporting, and dumping machine.

Joy walking miner

A continuous miner with a walking mechanism instead of crawler tracks. The walking mechanism was adopted to make the machine suitable for thin seams. The lowest crawler-track-mounted machine can operate in a minimum seam height of 4 ft (1.2 m), whereas the walking type can work in a 2.5-ft (0.76-m) seam. Syn: walking miner.

jubilee wagon

A small wagon, running on rails, which tips sideways.


Eng. Top jubs and bottom jubs, soft marly limestone, coarsely oolitic in places, in the Great Oolite at Kingsthorpe, Northamptonshire; also in the same formation at Bedford.


a. N. of Eng. A block of coal about 4 yd (3.7 m) square, holed and cut ready for breaking down.

b. In whole working, a portion of the coal laid out and ready for extraction; in pillar working (i.e., the drawing or extraction of pillars), the yet unremoved portion of a pillar. c. Applied to a working place, usually 6 to 8 yd (5.5 to 7.3 m) wide, driven in a pillar of coal. When a jud has been driven the distance required, the timber and rails are removed, and this is termed "drawing a jud." d. Som. See: jad; lift.


a. Derb.; Newc. A measuring stick to measure coal work underground. See also: judge rapper.

b. Eng. Formerly a youth who proved the holing.

judge rapper

The upper end of the vertical arm of a judge. See also: judge.

Judson powder

A blasting explosive containing sodium nitrate, sulfur, coal, and a little nitroglycerin.


A colloquial equivalent of seismic detector, geophone, etc. See also: geophone.


Timbers set obliquely against pillars of coal to carry a plank partition, making a triangular air passage or manway.


Possibly a tetragonal mineral, Na (sub 2) Co(SCN) (sub 4) .8H (sub 2) O ; a blue thiocyanate that may be an artifact.


Derb. The place where veins intersect.


Big Jumbler, a bed of limestone in the Lower Lias at Rugby, United Kingdom.


The thickest oolitic bed in the Carboniferous limestone of the Clee Hills, Shropshire, United Kingdom.


a. In mining, a drill carriage or mobile scaffold on which several drills of drifter type are mounted. It is used in tunnels and large headings.

b. An asbestos-fiberizing machine that is effective for moderately soft ore where crushing or breaking is not required. c. A mobile scaffold to assist drilling in large headings. d. A number of drills mounted on a mobile carriage and used in tunnels. e. Drilling platform used in tunneling.


a. See: jumping a claim.

b. A sudden rise in the dip of a coal seam.

jump correlation

Identification of events on noncontiguous seismic records as involving the same interfaces in the Earth.


a. The borer, steel, or bit for a compressed-air rock drill.

b. A long steel bar, or light aluminum tube with a steel end, used to dress rock faces, pry off loose rock, etc. c. Person who jumps a claim; i.e., takes possession of another's mining property. d. A steel bar used in manual drilling.

jumper bar

A weighted steel bar with a cutting edge; raised and dropped by hand.

jumping a claim

a. Taking possession of a mining claim liable to forfeiture owing to the requirements of the law being unfulfilled.

b. Taking possession of a mine or claim by stealth, fraud, or force. Syn: jump. c. The act of locating a mining claim on supposed excess ground within staked boundaries of an existing claim on the theory that the law governing the manner of making the original location had not been complied with.

jump sheet

A flat metal plate used as a turnsheet on which to turn the empty cars.


See: siderite. Also spelled junkerite.


a. The point where two or more passageways intersect horizontally or vertically.

b. In ventilation surveys, where three or more airways meet. c. The union of two lodes.

junction box

In mining, a stationary piece of enclosed apparatus from which one or more electric circuits for supplying mining equipment are connected through overcurrent protective devices to an incoming feeder circuit.


a. Any foreign metallic material accidentally introduced into a borehole.

b. Very poor or low-grade drill diamond.


See: siderite. Also spelled junckerite.


a. Eng. A bucket used for raising rock or ore in a shaft.

b. Eng. See: kibble.


a. The process of cutting a passage through a pillar of coal.

b. N. of Eng. An opening cut into, or a narrow slice taken off, a pillar in the room-and-pillar system of working coal. A fast junking is a narrow place driven lengthwise in a pillar of coal, but unholed into the room on either side of the pillar. A loose junking is a similar place driven along the side of the pillar and open to the room along that side.

junk mill

A bit designed to grind or cut foreign metallic material or junk in a borehole into pieces small enough to be washed out of the hole or recovered by a basket. CF: milling bit; rose bit.


a. Dev. Limestone concretions in slate.

b. Corn. Joints in rocks.

Jupiter process

A patented process for making cast steel by melting wrought-steel scrap with about 2.0% ferrosilicon, up to about 0.5% ferromanganese, and about 3.0% aluminum, then casting in molds of a special composition.

Jupiter steel

A steel produced by the Jupiter process; it is about as strong and as ductile as forged steel.


The second period of the Mesozoic Era (after the Triassic and before the Cretaceous), thought to have covered the span of time between 190 million years and 135 million years ago; also, the corresponding system of rocks. It is named after the Jura Mountains between France and Switzerland, in which rocks of this age were first studied.

jury rig

Any temporary or makeshift device, rig, or piece of equipment.


A small tub or truck used for gathering coal in thin seams.


a. Said of an ore-forming fluid or mineralizer that is derived from a magma, via fractional crystallization or other plutonic mechanism, as opposed to fluids of surface, connate, or meteoric origin.

b. A term applied to water and gases that are known to have been derived directly from magma and are thought to have come to the Earth's surface for the first time. c. In the classification of pyroclastics, the equivalent of essential; derived directly from magma reaching the surface.

juvenile water

Water from the interior of the Earth that is new or has never been a part of the general system of ground water circulation. CF: magmatic water.

juxtaposition twin

See: contact twin. CF: interpenetration twin.