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

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labeled atom

Atom rendered radioactive and thus traceable through a chemical process or a flow line. Also called tagged atom.


Said of rocks and minerals that are mechanically or chemically unstable; easily decomposed. CF: unstable.

labile protobitumens

Easily decomposable plant and animal products such as fats and oils or proteins that are found in peat and sapropels.


The property of bituminous emulsions, relating to the ease with which they break when put into use. Labile emulsions are quick breaking.


a. A shaft, cavity, or other part of a mine from which ore is being or has been extracted; a working, as a labor in a quicksilver mine. See also: working.

b. The annual assessment work required on claims calls for $100.00 of labor and improvements. In Australia, claims have continuous labor or are manned throughout the year. c. A Spanish term used in early land surveys in Texas for unit of area equal to about 177.14 acres (representing a tract 100 varas square). Pronounced la-bore.


In the iron and steel industry, the space between the fire and flue bridges of a reverberatory furnace in which the work is performed. Also called "kitchen and hearth."

La Bour centrifugal pump

A self-priming centrifugal pump containing a trap, which always ensures sufficient water for the pump to function, and also a separator to remove the entrained air in the water.


Optical diffraction of monochromatic light, commonly blue, caused by exsolution lamellae in some labradorite samples; appears to come from within the sample. CF: labrador moonstone.

labrador hornblende

See: orthopyroxene.


A triclinic mineral, (Ca,Na)[(Al,Si)AlSi (sub 2) O (sub 8) ] ; CaAl 70 to 50 mol % and NaSi 30 to 50 mol %; plagioclase series of the feldspar group; a common rock-forming mineral in basalt, gabbro, and anorthosite; also in hornfels and siliceous marble.

Labrador moonstone

A variety of labradorite displaying an internal play of colors. See: labradorescence.

Labrador rock

See: labradorite.


A monoclinic mineral, (K,Ba,Na)(Ti,Nb)(Si,Al) (sub 2) (O,OH) (sub 7) .H (sub 2) O . Also spelled labuntzovite; labountsovite.


a. A series of canals through which a stream of water is directed for sorting crushed ore according to its specific gravity.

b. A pipe or chamber of many turnings, for condensing metal vapors or fumes.


See: laccolith.


A concordant igneous intrusion with a known or assumed flat floor and a postulated, dikelike feeder commonly thought to be beneath its thickest point. It is generally plano-convex in form and roughly circular in plan, less than 5 miles (8 km) in diameter, and from a few feet to several hundred feet in thickness. See also: phacolith. Syn: laccolite.


Eng. Line cut, with the point of a pick, on slickensides.


a. The timber or other material placed behind and around the main supports. See also: lagging; lofting.

b. Strips or light bars of wrought iron bent over at the ends and wedged between the bars and the roof. c. Small boards or patches that prevent dirt from entering an excavation through spaces between sheeting or lagging planks. d. Bars placed diagonally to space and stiffen members, as in a built-up column. e. Eng. Wood placed inside the sets of timber as a tie from prop to prop. Also called stringing piece. See also: bracing. f. N. Staff. Timbers placed across the tops of bars or caps to secure the roof between the timbers.

lack clay

Ire. A thin pan under the moors.

LaCoste-Romberg gravimeter

A long-period vertical seismograph suspended system adapted to the measurement of gravity differences. Sensitivity is achieved by adjusting the system to proximity to an instability configuration.


A monoclinic mineral, NaAl(PO (sub 4) )F ; isostructural with durangite; in cavities in granite pegmatites.

lactic acid

In flotation, a depressant sometimes used to depress iron minerals.


Pertaining to, formed in, growing in, or inhabiting lakes.


a. The arm that carries the tumblers and bucket line of a dredge.

b. The continuous line of mud buckets, carried on an oblique endless chain, in a bucket ladder excavator or dredger. c. The digging boom assembly in a hydraulic dredge or chain-and-buckets ditcher.

ladder-bucket dredge

See: bucket-ladder dredge.

ladder ditcher

An excavator that digs ditches by means of a chain of traveling buckets supported by a boom.

ladder drilling

Arrangement used in large-scale rock tunneling. Retractable drills with pneumatic power legs are mounted on prefabricated steel ladders in tiers, connected into a holding frame or jumbo. As many as 22 drills can be worked simultaneously by a small labor force.

ladder lode

See: ladder vein.

ladder sollar

A platform at the bottom of each ladder in a series.

ladder vein

One of a series of mineral deposits in transverse, roughly parallel fractures that have formed along foliation planes perpendicular to the walls of a dike during its cooling or along shrinkage joints in basaltic rocks or dikes. Syn: ladder lode.


a. See: manway.

b. Mine shaft, raise, or winze between two main levels, equipped with ladders. c. The particular shaft or compartment of a shaft containing ladders. Also called ladder road.


a. Scot. A load.

b. A watercourse, ditch, or drain. c. The mouth of a river.

laded metal

Molten glass dipped from a melting pot to a casting table. Also called gathered metal.

lading hole

In glassmaking, an orifice through which melted glass is ladled or taken out by a cuvette.


a. In a smelter or foundry, a steel-holding vessel used in the transfer and transport of molten metal, matte, or slag.

b. A long-handled, cup-shaped tool for ladling glass out or from one spot to another. Also used for filling open pots.

ladle addition

In foundry work, addition of special metals (e.g., granulated nickel) or compounds (e.g., ferrosilicon) to molten iron in ladle to produce special qualities in castings.

ladle craneman

In the iron and steel industry, a person who places ladles under the tapholes of furnaces and holds them in position while the metal is poured into them. Also called charging floor crane operator; ladle crane operator; steel charger.

ladle filler

In metallurgy, a person who transfers molten metal from the furnace into a ladle and skims and fluxes metal preparatory to casting.

ladle furnace

A small furnace for calcining or melting substances in a ladle.

ladle liner

In ore dressing, smelting, and refining, a person who repairs and relines pouring ladles used to transport molten metals, such as iron, steel, and copper. Also called ladle cleaner; ladle dauber; ladle houseman; ladle mender; ladle patcher; ladle repairman.

ladle lip

A concave projection at the upper edge of a ladle to guide the metal in pouring.


Worker who pours molten glass from a suspended ladle on casting table for rolling into sheet glass.

Lafond's tables

A set of tables and associated information for correcting reversing thermometers and computing dynamic height anomalies; compiled by E.C. Lafond and published by the U.S. Navy Hydrographic Office as H.O. Pub. No. 617.


a. To place planks, slabs, or small timbers over horizontal, or behind upright, members of mine timber sets to form a ceiling or wall.

b. In flotation, any retardation of an output with respect to the causal input. c. A flattish piece of wood or other material to wedge the timber or steel supports against the ground and to secure the area between the supports. See also: lid; wedge. d. To protect a shaft or level from falling rock by lining it with timber (lagging). e. Time required for circulation liquid to travel downward from the drill pump through the drill string to the bit or upward from the bottom of the borehole to the collar. f. The lapse of time between the occurrence of an event or condition and its detection on a recording device. g. To provide or cover with lags; as, to lag a boiler with a nonconductor; to lag timbers in a mine. See also: lags; lagging. h. A distance class interval used for variogram computation.

lag deposit

See: lag gravel.


Ger. The enclosed pieces of older rocks in a sedimentary ore deposit.

lag fault

An overthrust, the thrusted rocks of which move differentially so that the upper part of the geologic section is left behind; the replacement of the upper limb of an overturned anticline by a fold fault. Syn: tectonic gap.

lagged liner

A metal plate with raised areas, to be inserted in the bottom of shaker conveyor troughs and held in place by spot welding. The raised areas assist coal travel on steep grades or under wet conditions.


a. Lagging wedges and secures the roof and sides behind the main timber or steel supports in a mine and provides early resistance to pressure. If concrete slabs are used, they are made in lengths to fit between the arch webs. The lagging behind steel arches in tunnels may be pyrolith-treated, fire-resisting boards. Also called lacing.

b. Pieces of timber about 4 ft 6 in by 6 in by 2 in (1.4 m by 15 cm by 5 cm) with one end sharpened or beveled to give the lath an upward trend when being driven into the roof gravels. A number of laths driven into the roof form a protective shield for the miners working in the face. Sometimes called laths. c. In shafts, planks, usually 2 in, placed on the outside of sets. Coeur D'Alene lagging has 2-in by 2-in cleats nailed to the top and bottom of the wall and end plates about 2 in back from the outer edge. The lagging is then cut to fit between the plates and is placed against the cleats and flush with the plates on the outside. d. Narrow boards, generally planed, placed horizontally on the arch frames of a center. On this lagging the arch of masonry is built. The term is also applied to poling boards. e. Planks, slabs, or small timbers placed over the caps or behind the posts of the timbering, not to carry the main weight, but to form a ceiling or a wall, preventing fragments or rock from falling through. See also: lag. f. Heavy planks or timbers used to support the roof of a mine, or for floors of working places, and for the accumulation of rock and earth in a stope. g. Long pieces of timbers closely fitted together and fastened to the drum rings to form a surface for the rope to wind on. h. The narrow strips supporting an arch of masonry while in construction. i. The surface or contact area of a drum or flat pulley, esp. a detachable surface or one of special composition. j. Boards fastened to the back of a shovel for blast protection. k. Covering on boilers, tanks, and pipes used to provide thermal insulation. l. Material applied to pulleys to increase traction between the pulley and belt and to decrease wear on both. See also: backing deals. m. Verb. To install lagging.

lagging bar

See: roof stringer.

lag gravel

a. A residual accumulation of rock fragments remaining on a surface after the finer material has been blown away by winds. See also: desert pavement; pebble armor.

b. Coarse-grained material that is rolled or dragged along the bottom of a stream at a slower rate than the finer material, or that is left behind after currents have winnowed or washed away the finer material. Syn: lag; lag deposit.


Fr. In sheet glass manufacture, a sheet of perfectly smooth glass, interposed between the flattening stone and the cylinder that is to be flattened.


Eng. Long pieces of timber closely fitted together and fastened to oak curbs or rings forming part of a drum used in sinking through quicksand or soft ground. CF: lag.

lag screw

a. A square-headed, heavy wood screw. It must be tightened down with a wrench because its head is not slotted.

b. A flat-headed machine screw by which to fasten wood lagging, as on a curve surface.

lag time

The total time between the initial application of current and the rupture of the circuit within the detonator.


See: mudflow.


Black monoclinic mineral, Fe (super 2+) Fe (sub 2) (super 3+) (SiO (sub 4) ) (sub 2) .


Clay; mud; mire.


A trigonal mineral, Bi (sub 4) (Se,S) (sub 3) . Syn: selenjoseite.

lake-bed placer

In Alaska, a placer in the bed of a present or ancient lake; generally formed by landslides or glacial damming.

Lake copper

Copper produced from the Lake Superior ores in which the metal occurs native and is of high purity.

Lake George diamond

See: Herkimer diamond.

lake ore

a. See: bog iron; bog iron ore.

b. A disklike or irregular concretionary mass of ferric oxyhydroxide less than 1 m thick; or a layer of porous, yellow bedded limonite formed along the borders of certain lakes. See also: bog ore.

Lake Superior agate

a. Any agate from the Lake Superior region.

b. Thompsonite marked or banded like agate from the Lake Superior region.

Lake Superior greenstone

See: pumpellyite.

lambda plate

See: mica plate.

Lambert's Law

See: translucency.


A thin scale, leaf, lamina, or layer; e.g., one of the units of a polysynthetically twinned mineral, such as plagioclase. Plural, lamellae.


Composed of or arranged in lamellae; disposed in layers like the leaves of a book. Syn: lamellate.

lamellar flow

Flow of a liquid in which layers glide over one another. CF: laminar flow.

lamella roof

A vault or large span built up with short structural members of timber or pressed steel, joined together in a diamond pattern by bolting or other suitable connections. This system, which is a type of stressed-skin construction, was patented in 1925 by a German engineer.

lamellar pyrite

See: marcasite.

lamellar stellate

In mineralogy, having or consisting of lamellae arranged in groups resembling stars.

lamellar twinning

Multiple parallel twins; e.g., albite twinning in plagioclase. Syn: polysynthetic twinning.


See: lamellar.


Widening a passage by cutting coal from the side of it. Also called skipping; slicing.


The thinnest recognizable layer in a sedimentary rock. Plural, laminae. CF: stratum.

laminar flow

Water flow in which the stream lines remain distinct and the flow direction at every point remains unchanged with time. It is characteristic of the movement of ground water. CF: turbulent flow; lamellar flow. Syn: streamline flow; sheet flow.

laminar velocity

That velocity below which, in a particular conduit, laminar flow will always exist, and above which the flow may be either laminar or turbulent, depending on circumstances. Also known as lower critical velocity.


In very thin parallel layers.

laminated iron

Iron in the form of thin sheets; used as cores of transformers, etc. The losses due to eddy currents with laminated iron cores are lower when compared with solid cores.

laminated quartz

Vein quartz containing slabs, blades, or laminar films of other material.

laminating machine

A set of rolls or any apparatus for making thin plates of metal, such as gold, preliminary to beating.

laminating roller

The adjustable roller in a rolling mill whereby the thickness of rolled metal sheets is regulated.


a. The formation of a lamina or laminae.

b. The state of being laminated; specif. the finest stratification of bedding, typically exhibited by shales and fine-grained sandstones. c. A laminated structure.


Of rocks, bedding in layers less than 1 cm thick; formation with thin layers that vary in grain or composition.


a. Partings in coal seams.

b. N. of Eng. A collier's term for accidents of almost every description to people working in and about the mines. A variation of lame, to cripple or disable.


a. See: safety lamp.

b. A small handheld electrical device that produces an intense ultraviolet radiation, called "black light." See: black light; fluorescent lamp. c. An electrical lamplike device producing intense ultraviolet radiations for visually examining drill cores or rock specimens for the presence and/or abundance of fluorescent minerals.


Wad containing 4% to 18% copper oxide and commonly cobalt. Syn: cupreous manganese.

lamp cabin

a. A place above ground where the safety and cap lamps are maintained, before being handed to the workers.

b. See: lamp room.

lamp cleaner

See: lampman.

lamp cup

A means for supporting a flame safety lamp on a tripod to provide a sight for surveying.

lamp house

See: lamp cabin.


In prospecting, use of a portable ultraviolet lamp to reveal fluorescent minerals.

lamp keeper

See: lampman.


a. The person in charge of the lamp room at a mine responsible for the maintenance of the safety lamps.

b. In mining, one who cleans, tests, and repairs lamps used underground by miners. Also called battery charger; lamp cleaner; lamp-house man; lamp keeper; lamp repairer; safety-lamp keeper.

lamp rack

A rack upon which electric cap lamp batteries are placed to be charged.

lamp repairer

See: lampman.


See: oxyhornblende.


A group name for dark-colored hypabyssal or extrusive rocks rich in potassium and magnesium; also, any rock in that group, such as madupite, orendite, fitzroyite, verite, cedricite, or wyomingite.

lamp room

A room or building at the surface of a mine provided for charging, servicing, and issuing all cap, hand, and flame safety lamps held at the mine. See also: self-service system.


A monoclinic mineral, Na (sub 2) (Sr,Ba) (sub 2) Ti (sub 3) (SiO (sub 4) ) (sub 4) (OH,F) (sub 2) . Syn: molengraafite.


A group of dark-colored, porphyritic, hypabyssal igneous rocks characterized by panidiomorphic texture, a high percentage of mafic minerals (esp. biotite, hornblende, and pyroxene), which form the phenocrysts, and a fine-grained groundmass with the same mafic minerals in addition to feldspars and/or feldspathoids; also, any rock in that group. Most lamprophyres are highly altered. They are commonly associated with carbonatites. CF: leucophyre. Adj: lamprophyric.


Said of the holocrystalline-porphyritic texture exhibited by lamprophyres, in which phenocrysts of mafic minerals are contained in a fine-grained crystalline groundmass.


Metamorphosed lamprophyre with a schistose structure containing brown biotite and green hornblende.

lamp station

a. Fixed places in the intake airway of a coal mine where the miners' safety lamps are externally examined by a deputy before the workers proceed to their working places. In a safety lamp mine, the lamp station is the only place where flame safety lamps may be opened and relighted.

b. Locations in gaseous mines where safety lamps are opened, cleaned, and refilled or charged by a qualified attendant. c. A place underground, appointed for the examination, by an official, of safety lamps in use. d. A lamp room.


A subdivision of the Coal Measures--based mainly on plant fossils. It represents in part, the millstone grit of South Wales; well developed in South Scotland, where coal seams are present.


A monoclinic mineral, Pb (sub 2) (SO (sub 4) )O ; perfect basal cleavage; named for Lanarkshire, Scotland.

Lancashire bord-and-pillar system

See: bord-and-pillar method.

Lancashire method

A method of working moderately inclined coal seams. The first stage consists of splitting a panel of coal into pillars and as a second stage the pillars are extracted on the retreat by a longwall face.


A short sluice used for cleaning tin concentrate.


a. To set or allow the bottom end of a drivepipe or casing to rest at a preselected horizon in a borehole.

b. For reamers, drills, and taps, the solid section between the flutes.

land accretion

Reclamation of land from the sea or other low-lying or flooded areas by draining and pumping, dumping of fill, or planting of marine vegetation.

land chain

A surveyor's chain of 100 links.

land compass

A surveyor's compass.


a. A worker stationed at one of the levels of a mine shaft to unload rock from the bucket or cage and load drilling and blasting supplies to be lowered to the crew.

b. In the quarry industry, one who supervises and assists in guiding, steadying, and loading, on trucks or railroad cars, blocks of stone hoisted from the quarry floor. Syn: top hooker. c. In metal mining, a laborer who (1) cleans skips by directing a blast of compressed air into them through a hose; (2) records number of loaded skips hoisted to surface; and (3) loads railroad cars with ore from bins by raising and lowering chute doors. d. In anthracite coal mining, bituminous coal mining, or metal mining, one who works with shaft sinking crew at top of shaft or at a level immediately above shaft bottom, dumping rock into mine cars from a bucket in which it is raised. Also called bucket dumper; landing tender; top lander. e. Eng. The person who receives the loaded bucket or tub at the mouth of the shaft. Also called banksman.


A pink or rose variety of grossular in dodecahedra. Syn: rosolite; xalostocite.


An orthorhombic mineral, (Mn,Mg) (sub 9) Fe (sub 3) (PO (sub 4) ) (sub 8) (OH) (sub 3) .9H (sub 2) O .


Any physical, recognizable form or feature of the Earth's surface, having a characteristic shape, and produced by natural causes; it includes major forms such as plain, plateau, and mountain, and minor forms such as hill, valley, slope, esker, and dune. Taken together, landforms make up the surface configuration of the Earth. Syn: relief feature.

landform system

A group of related natural features, objects, or forces; e.g., a drainage system or a mountain system. See also: mountain system.


a. The top or bottom of a slope, shaft, or inclined plane.

b. The mouth of a shaft where the cages are unloaded; any point in the shaft at which the cage can be loaded with people or materials. c. The brow or level section at the top of an inclined haulage plane where the loaded tubs are exchanged for empty tubs, or vice versa. See also: apex. d. A preselected and prepared horizon in a borehole on or at which the bottom end of a drivepipe or casing string is to be set. e. A platform from which to charge a furnace. f. Level stage in a shaft at which cages are loaded and discharged.

landing box

Scot. The box into which a pump delivers water.

landing shaft

S. Wales. A shaft through which coal is raised.

landing tender

See: lander.

land pebble

See: land-pebble phosphate.

land-pebble phosphate

A term used in Florida for a pebble phosphate occurring as pellets, pebbles, and nodules in gravelly beds a few feet below the ground surface. It is extensively mined. Syn: land pebble; land rock; matrix.

land plaster

Finely ground gypsum used as a fertilizer.

land rock

A syn. used in South Carolina for land-pebble phosphate.


Multispectral data from satellite remote sensing imagery that provides landscape patterns reflecting geologic structures, types of rocks, and vegetation.

landscape agate

See: moss agate.

landscape marble

A close-grained limestone characterized by dark conspicuous dendritic markings that suggest natural scenery (woodlands, forests); e.g., the argillaceous limestone in the Cotham Marble near Bristol, England. Syn: forest marble.


A general term covering a wide variety of mass-movement landforms and processes involving the downslope transport, under gravitational influence, of soil and rock material en masse. Usually the displaced material moves over a relatively confined zone or surface of shear. The wide range of sites and structures, and of material properties affecting resistance to shear, result in a great range of landslide morphology, rates, patterns of movement, and scale. Landsliding is usually preceded, accompanied, and followed by perceptible creep along the surface of sliding and/or within the slide mass. Terminology designating landslide types generally refers to the landform as well as the process responsible for it; e.g., rockfall, translational slide, block glide, avalanche, mudflow, liquefaction slide, and slump. Syn: landsliding; slide; landslip.


See: landslide.


A British syn. of landslide.

land subsidence

See: subsidence.

lands valuable for minerals

As used in the mining law, applies to all lands chiefly valuable for nonmetalliferous deposits, such as alum, asphaltum, borax, guano, diamonds, gypsum, marble, mica, slate, amber petroleum, limestone, and building stone, rather than for agricultural purposes. Such lands are subject to disposition by the United States under the mining laws only.

land weight

Lanc. The pressure exerted by the subsidence of the cover or overburden.

Lane mill

A slow-speed roller mill of the Chilean type. A horizontal spider carrying six rollers revolves slowly in a pan 10 ft (3 m) or more in diameter, making about 8 rpm.


A trigonal mineral, (Mn,Ca) (sub 4) (Mn,Fe) (sub 9) SbSi (sub 2) O (sub 24) ; in skarns. Also spelled laangbanite. (Not langbeinite.)


An isometric mineral, K (sub 2) Mg (sub 2) (SO (sub 4) ) (sub 3) ; associated with halite and sylvite in marine evaporite deposits; a source of potash. (Not langbanite.)


A monoclinic mineral, Cu (sub 4) (SO (sub 4) )(OH) (sub 6) .2H (sub 2) O ; in blue-green concretionary crusts; in Cornwall, U.K., and Stredoslovensky, Slovakia.

lang lay rope

A rope in which the wires are twisted in the same direction as the strands and the wires are thus exposed to wear for a much greater length than in round rope. The smoother lang lay resists wear to better advantage and is frequently preferred for haulage ropes. Syn: universal lay rope.

Langmuir's adsorption isotherm

The equation for calculating a gas monolayer on a flat surface.

Langmuir trough

Rectangular tank used to measure the surface tension of a monolayer adsorbed at the surface of a liquid.

Lang's lay rope

See: winding rope.


A monoclinic mineral, MgCO (sub 3) .5H (sub 2) O ; forms small stalactites that alter to nesquehonite in mines near Lansford, PA.


Enclosed light (candle or oil) carried by a mine worker.


An orthorhombic mineral, (Ce,La,Nd) (sub 2) (CO (sub 3) ) (sub 3) .8H (sub 2) ) ; further speciated according to its predominant rare-earth element; in pegmatites and carbonate-rich sediments.

lanyon shield

An iron curtain, stiffened by ribs of angle iron, suspended from trolley wheels running on a rail parallel with and in front of a furnace to protect the worker from the furnace heat.


a. One coil of rope on the winding drum of the mine hoist.

b. Polishing cloth used in preparing polished mineral specimens by abrasive grinding. c. A surface defect, appearing as a seam, caused by folding over hot metal, fins, or sharp corners and then rolling or forging them into the surface, but not welding them. d. To dimension, smooth, or polish (as a metal surface or body) to a high degree of refinement or accuracy. e. An imperfection; a fold in the surface of a glass article caused by incorrect flow during forming. f. A tool used for polishing glass. g. A rotating disk of soft metal or wood, used to hold polishing powder for cutting or polishing gems or metal.


Impure sandy green limestone with shaly partings in the Middle Purbeck beds, Swanage, U.K. Also spelled leaper; leper.


a. An artificer who cuts, polishes, or engraves gems or precious stones.

b. Person who is skilled in the nature and kind of gems or precious stones; a connoisseur of lapidary work.


Pyroclastics that may be either essential, accessory, or accidental in origin, of a size range that has been variously defined within the limits of 2 mm and 64 mm. The fragments may be either solidified or still viscous when they land (though some classifications restrict the term to the former); thus there is no characteristic shape. An individual fragment is called a lapillus. CF: cinder.


Having the form of small stones.

lapis lazuli

a. A lazurite-bearing rock; contains lazurite or hauyne (possibly zeolitized), diopside, edenitic amphibole (koksharovite), muscovite, calcite, and pyrite; occurs in various shades of blue; possibly the original sapphire of the ancients; Syn: azure; lazuli.

b. Gem-quality lazurite. (Not lazulite.) c. An ultramarine-colored serpentine in India. See also: ultramarine.

lapis matrix

Lapis lazuli (lazurite) containing prominent patches of calcite. See also: Chilean lapis; lazurite.

LaPointe picker

Miniature belt conveyor, on which small ore particles move singly past a Geiger-Mueller tube that is set to operate a sorting device. This removes from the passing stream each particle of radioactive ore that reaches the required intensity, therefore sorting out the valuable material.


a. Overlapped and fitted together.

b. The act of polishing or grinding on a lap.

Laramide orogeny

A time of deformation, typically recorded in the eastern Rocky Mountains of the United States, whose several phases extended from late Cretaceous until the end of the Paleocene. It is named for the Laramie Formation of Wyoming and Colorado, probably a synorogenic deposit.

Laramide revolution

See: Laramide orogeny.


See: laurdalite.


A monoclinic mineral, (NH (sub 4) )B (sub 5) O (sub 6) (OH) (sub 4) .


a. White hydrated silica, probably a variety of opal; occurring in clay in central Russia.

b. Massive talc. Syn: steatite; agalmatolite. c. A massive variety of muscovite and/or pyrophyllite. See also: pagodite.

lard oil

An oil produced from animal fats. This oil is an efficient lubricant for use on metal-cutting tools.


Massive talc; steatite.

lard stone

A kind of soft stone found in China. See also: steatite; agalmatolite.


Eng. The largest lumps of coal sent to the surface, or all coal that is handpicked or does not pass over screens; also the largest coal that passes over screens.

large coal

a. One of the three main size groups by which coal is sold by the National Coal Board of Great Britain. Large coal has no upper size limit and has a lower size limit of 1-1/2 to 2 in (3.8 to 5.1 cm) and embraces large screened coal, cobbles, and treble sizes. See also: graded coal; smalls.

b. Coal above an agreed size without any upper size limit. Also called lump coal.

large colliery

Gr. Brit. In general, a colliery producing more than 1,500 st/d (1,360 t/d).

large-diameter boring machine

An auger-type coal-cutting machine developed by the U.S. Bureau of Mines for use in anthracite mining. It can drill holes 1 ft (31 cm) in diameter, 300 ft (91 m) long, and larger holes for shorter distances.

large knot

A large knot is one whose average diameter exceeds one-third the width of the surface on which it appears; but such a knot may be allowed if it occurs outside the sections of the mine track tie between 6 in and 18 in (15 cm and 46 cm) from each end.

large shake

A large shake is one that exceeds one-third the width of the mine track tie. A shake not exceeding this limitation and that does not extend nearer than 1/2 in (1.3 cm) to any surface shall be permissible.

large split

A term applying to mine track ties. A large split is a split exceeding 5 in (13 cm) in length. Splits not longer than 5 in are permissible providing satisfactory antisplitting devices have been properly applied.


A monoclinic mineral, 4[beta-Ca (sub 2) SiO (sub 4) ] ; gray; in contact metamorphosed limestone. CF: bredigite.


An orthorhombic mineral, PbZnSiO (sub 4) ; forms colorless to white prisms; in veins at Franklin, NJ.

Larsen's pile

A type of pile consisting of hollow cylinders that increase resistance against bending and crumpling. They are esp. useful in shaft sinking in sand and gravel.

Larsen's spiles

Steel sections of various forms, made esp. to resist bending, that are used in place of wooden spiles in forepoling.

Larson ledge finder

A tool used to reach bedrock when the driven pipe has failed.


An alkalic syenite, grading to monzonite, composed of phenocrysts of two feldspars (esp. oligoclase and alkali feldspar), often intimately intergrown, which comprise up to 90% of the rock, with diopsidic augite and titanaugite as the chief mafic minerals, and accessory apatite (generally abundant), ilmenite, and titaniferous magnetite, and less commonly olivine, bronzite, lepidomelane, and quartz or feldspathoids (less than 10% by volume). Its name, given by Broegger in 1890, is derived from Larvik, Norway. Also spelled laurvikite. Syn: blue granite.


An active electron device that converts input power into a very narrow, intense beam of coherent visible or infrared light; the input power excites the atoms of an optical resonator to a higher energy level, and the resonator forces the excited atoms to radiate in phase. Derived from "light amplification by stimulated emission of radiation." See also: maser.


To attach a chain to a haulage rope by wrapping or lapping the end of the chain around the rope, the other end being attached to a mine wagon.


a. A native employed to do lashing. See also: lashing.

b. See: mucker.


A person employed to lash the chains from the tubs to the endless rope, in underground mechanical haulage.


a. Any of a number of planks nailed inside of several frames or sets in a shaft to keep them in place. Also called listing.

b. A binding, generally of light line around the end of a rope. c. In South Africa, loading broken rock or ore with shovels. d. Shoveling rock downstope to ore passes--work performed by a lasher. A "lasher-on" connects tubs or trucks to a rope haulage. Also called mucking.

lashing chain

A short chain to attach tubs to an overrope in endless rope haulage by wrapping it around the rope. The chain may be about 12 ft (3.7 m) long, of low manganese steel, with 3/8-in-diameter (9.5-mm-diameter) standard links. At one end of the chain, a ring 4 in (10.2 mm) in diameter is attached to the drawbar hook of the tub, and to a hook about 3/8 in in diameter to secure it to the rope at the lashing end. On an undulating road, two lashing chains may be necessary--one forward and one rear of the tub.


Extemporized engineering rig for a temporary job.


A thin, flat diamond with a simple facet at the side; used by Indian cutters to cover miniature paintings. Also spelled lask. Also called portrait stone.

last lift

N. of Eng. The last rib or jud to come off a pillar.


a. The locking device on a hoist hook, elevator, lifting bail, etc.

b. The inner-tube locking and unlocking device in the head of a wire-line core barrel.


a. Applied to the split rail and hinged switches. Syn: switch.

b. Hinged switch points, or short pieces of rail that form rail crossings.

late magmatic mineral

A mineral formed during the late stages of magmatic activity, between the main stage of crystallization and the pegmatitic stage.

latent heat

Thermal energy absorbed or emitted in a process (as fusion or vaporization) other than change of temperature. CF: sensible heat.

latent heat of fusion

The amount of heat required to change 1 g of a substance at the temperature of its melting point from the solid to the liquid state without changing temperature.


a. A hard heading that branches off a horizon, in horizon mining, along the strike of the seams. It may be from 14 to 20 ft (4.3 to 6.1 m) wide. At intervals of 1,000 to 1,500 yd (910 to 1,400 m) along the lateral, crosscut roads are driven at right angles to intersect and develop the coal seams. From the crosscuts, conveyor panels are opened out in the seams. In general, the term lateral is also applied to any coal heading driven in a sideways direction.

b. Belonging to the sides, or to one side. c. A horizontal mine working. d. Situated on or at, or pertaining to, a side. e. A conduit diverting water from a main conduit, for delivery to distributaries. f. A secondary ditch.

lateral cleavage

Cleavage parallel to the lateral planes.

lateral development

Any system of development in coal seams or thick orebodies in which headings are driven horizontally across the coal or ore and connected to main haulage drifts, entries, or shafts. There are many variations and modifications depending on the thickness, shape, and inclination of the deposit. See also: horizon mining.

lateral deviation

The horizontal distance by which a borehole misses its intended target.

lateral draw

The angle of draw over a strike face or over workings in a flat seam.

lateral secretion

A theory of ore genesis formulated in the 18th century and passing in and out of use since. It postulates the formation of ore deposits by the leaching of adjacent wall rock. In current usage, convectively driven fluids associated with cooling plutons are thought to have abstracted metals from adjacent host rocks and transported them to new sites of deposition, as in the formation of certain porphyry base-metal deposits. See also: lithogene; segregated vein.

lateral support

Means whereby walls are braced either vertically or horizontally by columns, pilasters, or crosswalls, or by floor or roof constructions, respectively.

later arrival

A signal that is recorded on a seismogram later than the first arrival of energy.


Red residual soil developed in humid, tropical, and subtropical regions of good drainage. It is leached of silica and contains concentrations particularly of iron oxides and hydroxides and aluminum hydroxides. It may be an ore of iron, aluminum, manganese, or nickel. Adj. lateritic. Syn: latosol.


The electrical resistivity of coal appears to decrease with ash content. The laterlog measures what is virtually the true resistivity of the coal and may ultimately provide information on seam quality. The laterlog uses a sheet of current that is focused on each formation in succession and so measures the resistivity of that formation only. The mud column or a salty mud has no effect on the measured resistivity. The laterlog may be measured by a seven- or three-electrode arrangement but the former is preferred.

latex cement

A specialized cementing material consisting of a portland-type cement, latex, a surface-active agent, and water, having a setting time equivalent to a neat portland-cement slurry. Latex cement shrinks less and is tougher, stronger, less permeable, and more durable than portland cement.

Latex spray

Trade name for a synthetic rubber fluid, which, when sprayed onto underground stoppings, forms a tough nonflammable coating thus preventing air feeding fires or heatings, or air leakages through doors, surface air locks, and air crossings. Also called Latex sealant.


a. A board or plank sharpened at one end, like sheet piling, used in roofing levels or in protecting the sides of a shaft through a stratum of unstable earth. See: spill.

b. A long, thin mineral crystal.

lath frame

A weak lath frame, surrounding a main crib, the space between being for the insertion of piles.


Refers to crystals with three distinctly different dimensions. CF: acicular; tabular; rodlike; equant.


a. Corn. The boards or lagging put behind a frame of timber.

b. Corn. Pieces of timber about 4 ft 6 in by 6 in by 2 in (1.4 m by 15 cm by 5 cm) with end sharpened or beveled to give the lath an upward trend when being driven into the roof gravels. A number of laths driven into the roof form a protective shield for the miners working in the face. Also called lagging.


A porphyritic extrusive rock having phenocrysts of plagioclase and potassium feldspar in nearly equal amounts, little or no quartz, and a finely crystalline to glassy groundmass, which may contain obscure potassium feldspar; the extrusive equivalent of monzonite. Latite grades into trachyte with an increase in the alkali feldspar content, and into andesite or basalt, depending on the presence of sodic or calcic plagioclase, as the alkali feldspar content decreases. It is usually considered synonymous with trachyandesite and trachybasalt, depending on the color. The name, given by Ransome in 1898, is derived from Latium, Italy.

latitude correction

a. The north-south correction made to observed magnetic-field intensity in order to remove the Earth's normal field (leaving, as the remainder, the anomalous field).

b. A correction of gravity data with latitude, because of variations in centrifugal force owing to the Earth's rotation and because of differences in the radius owing to polar flattening. The correction for latitude phi amounts to 1.308 sin 2 phi mgal/mi = 0.813 sin 2 phi mgal/km.


See: laterite.


A pink anorthite from Amitok Island, LB, Canada.


Metal in thin sheets, esp. (and originally) brass, which in this form is also called latten brass.


An array of points in space such that each point is in an identical point environment. Thus, any straight line drawn between any two points in a lattice and continued will pass at equal intervals through a succession of similar points. Fourteen possible lattices exist. Syn: Bravais lattice; space lattice. CF: net; row.

lattice constant

See: lattice parameter.

lattice energy

Energy required to separate the ions of an ionic crystal to an infinite distance from each other.

lattice girder

An open girder, beam, or column in timber, steel, or aluminum alloy, built up from structural members joined and braced together by intersecting diagonal bars. See also: space lattice.

lattice parameter

Lattice parameters are the unit lengths along each crystallographic axis and their interaxial angles. See also: axial element.

lattice texture

a. In mineral deposits, a texture produced by exsolution in which elongate crystals are arranged along structural planes.

b. A texture that is typical of the mineral serpentine in a rock where it replaces an amphibole. CF: knitted texture.

lattice water

a. Water that is an integral part of the clay structure. This structural water (OH lattice water) is not to be confused with interlayer water. The lattice water can be removed by heating in the range of about 450 to 600 degrees C.

b. Molecular water at specific lattice sites.


See: natrolite.


Alternate spelling of laubanite.

Laue diagram

See: Laue photograph. CF: crystallogram.


A triclinic mineral, MnFe (sub 2) (PO (sub 4) ) (sub 2) (OH) (sub 2) .8H (sub 2) O ; dimorphous with stewartite.

Laue photograph

A collection of X-ray diffraction spots made by a crystal using a Laue camera and white radiation. Syn: Laue diagram. CF: crystallogram.


a. A flume, trough, channel, or chute by which water or powdered ore is conveyed in a mining operation.

b. An inclined channel, lined with refractory material, for the conveyance of molten steel from the furnace taphole to a ladle. Also spelled lander.

launder man

In ore dressing, smelting, and refining, a laborer who maintains and repairs the launders (long boxes), used to convey water and mill pulp between the various units of ore-treating equipment in a mill.

launder screen

A screen used for the sizing and dewatering of small sizes of anthracite.

launder separation process

In this process, a stream of fluid carries the material to be separated down a channel provided with draws for separating a heavy-gravity product and means for overflowing a lighter one. If properly constructed and operated, a comparatively solid bed of material will form on the bottom of the launder. Above this bed, a layer of particles will move along by the stream at a comparatively slow speed. Above this, successive layers will move with greater and greater velocity.

launder washer

A type of coal washer in which the coal is separated from the refuse by stratification due to hindered settling while being carried in aqueous suspension through a trough. Modern launder washers have various mechanisms for continuously removing refuse from the bottom of the trough. Early launder washes were intermittent in operation.

laundry box

The box at the surface receiving the water pumped up from below.


Hypothetical continent in the Northern Hemisphere that broke up about the end of the Carboniferous Period to form the present northern continents.


An alkalic syenite containing more than 10% modal feldspathoids and characterized by porphyritic texture. Also spelled lardalite. The name, given by Broegger in 1890, is for Laurdal, Norway.

Laurentian granite

A name that was originally applied to Precambrian granites of the Laurentian Highlands, eastern Canada, and later to the oldest granites near the U.S.-Canadian border northwest of Lake Superior.


An orthorhombic mineral, PbCl(OH) ; dimorphous with paralaurionite; in ancient lead-ore slags.


An isometric mineral, RuS (sub 2) ; pyrite group; occurs with other platinum-group minerals in ultramafic and placer deposits.

lauroleic acid

Unsaturated fatty acid, C (sub 12) H (sub 22) O (sub 2) .


See: larvikite.


A monoclinic mineral, Fe (sub 2) (SO (sub 4) ) (sub 3) .6H (sub 2) O .


A monoclinic mineral, Ca(IO (sub 3) ) (sub 2) .

Lauth mill

Mill with three rolls, the middle roll being much smaller than the other two. Only the two larger rolls are driven, work being performed between the bottom and middle and middle and top rolls alternately; the roll setting is adjusted between passes.


An orthorhombic mineral, CuAsS .

lava breccia

See: volcanic breccia.

lava dome

A dome-shaped mountain of solidified lava in the form of many individual flows, formed by the extrusion of highly fluid lava, e.g., Mauna Loa, HI. See also: shield volcano.


A place where gold is obtained by washing.


See: amethystine quartz.


A monoclinic mineral, (Na,Ca) (sub 2) (Mn,Fe)(Zr,Ti)Si (sub 2) O (sub 7) (O,OH,F) (sub 2) . Also spelled laavenite.


A metamorphosed basaltic rock with relict phenocrysts of labradorite in an amphibolitic groundmass. The term was originated by Sederholm in 1899, who named it after Lavia, Finland.


A chromian variety of diopside. Also spelled lavroffite; lawrowite.


A fine-mesh gauze used as a sieve for clay.

law of cosines

In trigonometry, a law stating that in any triangle the square of one side equals the sum of the squares of the two other sides minus twice the product of these two other sides multiplied by the cosine of the included angle.

law of equal volumes

In ore genesis, the statement that during the formation of ore by replacement there is no change in rock volume or form. Syn: Lindgren's volume law.

law of extralateral rights

See: apex law.

law of gravitation

The law, discovered by Sir Isaac Newton, that every particle of matter attracts every other particle of matter, and the force between them is proportional to the product of their masses divided by the square of their distance apart. See also: gravitation; gravity.

law of mass action

The rate of a chemical reaction is directly proportional to the molecular concentrations of the reacting substances.

law of motion

A statement in dynamics that a body at rest remains at rest and a body in motion remains in uniform motion in a straight line unless acted upon by an external force. The acceleration of a body is directly proportional to the applied force and is in the direction of the straight line in which the force acts. For every force there is an equal and opposite force or reaction.

law of refraction

a. When a wave crosses a boundary, the wave normal changes direction in such a manner that the sine of the angle of incidence between wave normal and boundary normal divided by the velocity in the first medium equals the angle of refraction divided by the velocity in the second medium.

b. Light, upon crossing a boundary between two transparent substances of different optical densities, changes direction according to n (sub 2) /n (sub 1) =sin i, where n (sub 1) is the refractive index (RI) for the incident light ray making an angle i, and n (sub 2) is the RI for the refracted light ray making an angle r with the boundary (n (sub 1) < n (sub 2) ). Light rays refracted according to this law are called "ordinary" rays. CF: critical angle; extraordinary ray; ordinary ray; total reflection. Syn: Snell's law.

law of sines

In trigonometry, a law stating that in any triangle (either right or oblique) the sides are proportional to the sines of their opposite angles.

law of superposition

A general law upon which all geologic chronology is based: In any sequence of sedimentary strata (or of extrusive igneous rocks) that have not been overturned, the youngest stratum is at the top and the oldest at the base; i.e., each bed is younger than the bed beneath, but older than the bed above it. The law was first clearly stated by Steno (1669).


An orthorhombic mineral, 4[CaAl (sub 2) Si (sub 2) O (sub 7) (OH) (sub 2) .H (sub 2) O] ; dimorphous with partheite; pale blue; Mohs hardness, 8; in high-pressure, low-temperature schists.


See: vauquelinite.


a. The direction, or length, of twist of the wires and strands in a rope.

b. The length of lay of wire rope is the distance parallel to the axis of the rope in which a strand makes one complete turn about the axis of the rope. The length of lay of the strand, similarly, is the distance in which a wire makes one complete turn about the axis of the strand. c. To close or withdraw from work; said of collieries. d. The pitch or angle of the helix of the wires or strands of a rope, usually expressed as the ratio of the diameter of the strand or rope to the length required for one complete twist. e. Prov. Eng. A standard of fineness for metals; possible from the Spanish ley.


a. Siding in otherwise single-track underground tramming road.

b. A term used for an underground siding at or near a shaft for storing empty mine cars. c. See: bank.


a. A bed or stratum of rock.

b. One of a series of concentric zones or belts of the Earth, delineated by seismic discontinuities. A classification of the interior of the Earth that designates layers A to G from the surface inward.

layer depth

Thickness of the mixed surface layer of water.


N. of Eng. Choked up with sediment or mud.


See: bedding.

layering number

A dimensionless number, the value of which, taken in conjunction with inclination, roughness, and whether the ventilation is ascensional or descensional, determines the mixing and movement of combustible gases roof layers.

layering of combustible gases

The formation of a layer of combustible gases at the roof of a mine working and above the ventilating air current.


Procedure for loading coal in railroad cars in horizontal layers. Layer-loading is a simple and inexpensive method for smoothing out the irregularities in coal and consists in shuttling two to six railroad cars, hooked together, past the loading boom two or more at a time. This results in a more uniform product.

laying out

See: setting out.

lay of rope

See: winding rope.

lay of the land

See: topography.


a. The design or pattern of the main roadways and workings. The proper layout of mine workings is the responsibility of the manager aided by the planning department.

b. The map of a mine or part of a mine, usually including future workings arrangement. c. Diagram showing disposition of machines in a mill's flow line.

lay rope

Ordinary lay rope has the wires twisted in a direction opposite to the twist of the strands in the rope. The pitch of wire is from 2-1/2 to 3 times the diameter of the rope, and the pitch of the strands is from 6-1/2 to 9 times the diameter of the rope, the wires being exposed only in short lengths at intervals.


See: arsenosulvanite.


See: lapis lazuli. Also spelled lazule; lasule.


a. A monoclinic mineral, 2[MgAl (sub 2) (PO (sub 4) ) (sub 2) (OH) (sub 2) ] ; forms a series with scorzalite; azure blue; in granite pegmatites and quartz veins; may be a blue gemstone. Syn: azure spar; blue spar; false lapis; berkeleyite; klaprothine. (Not lazurite.)

b. The mineral group barbosalite, hentschelite, lazulite, and scorzalite.


Of, pertaining to, or having the characteristics of lazulite.


a. An isometric mineral, (Na,Ca) (sub 8) (Al,Si) (sub 12) (O,S) (sub 24) [(SO (sub 4) ),Cl (sub 2) ,(OH) (sub 2) ] of the sodalite group; deep blue to greenish blue; a contact metamorphic product in limestone; may be a blue gemstone (lapis lazuli). Also spelled lasurite. (Not lazulite.) See also: Chilean lapis. CF: ultramarine.

b. See: azure; azurite.

lazy balk

a. Eng. A timber placed at the top of a hopper, against which the top of the car strikes in dumping, to prevent the car from falling into the hopper.

b. Eng. The balk or girder held in position by a banger. Also called lazy girder.

lazy bench

The bench to one side of the drill tripod or derrick floor where visitors and workers can sit while observing the drilling operation.

lazy girder

See: lazy balk.

lazy tong conveyor

See: accordion roller conveyor.

L.D. steel process

Process in which oxygen is blown downwards at high velocity through a watercooled lance onto the surface of the hot metal contained in a basic lined vessel. To offset the intense heat produced, coolant materials are added with the original charge. These may be iron ore, sinter, or roll scale, but usually steel scrap is the main material used. As much as 26% of scrap may be used. After about 20 min, the charge is converted into liquid steel. During the process, tests and analyses are made and materials may be added to bring the metal to the required grade and temperature. See also: open-hearth process; O.L.P. steel process.