Mining Glossary J – L

Jaw crusher - A machine in which rock is broken by the action of steel plates.

Jig - A piece of milling equipment used to concentrate ore on a screen submerged in water, either by the reciprocating motion of the screen or by the pulsation of water through it.

KKimberlite - A variety of peridotite; the most common host rock of diamonds.- Planks or small timbers placed between steel ribs along the roof of a stope or drift to prevent rocks from falling, rather than to support the main weight of the overlying rocks.

Lagging – planks or small timbers placed between steel ribs along the roof of a stope or drift to prevent rocks from falling, rather than to support the main weight of the overlying rocks.

Lamprophyre - An igneous rock composed of dark minerals, that occurs in dykes; sometimes contains diamonds.

Laterite - A residual soil, ususally found in tropical countries, out of which the silica has been leached. May form orebodies of iron, nickel, bauxite and manganese.

Lounder - A chute or trough for conveying pulp, water or powdered ore in a mill.

Lava - A general name for the molten rock ejected by volcanoes. Leachable - Extractable by chemical solvents.

Leaching - A chemical process for the extraction of valuable minerals from ore; also, a natural process by which ground waters dissolve minerals, thus leaving the rock with a smaller proportion of some of the minerals than it contained originally.

Lens - Generally used to describe a body of ore that is thick in the middle and tapers towards the ends.

Lenticular - A deposit having roughly the form of a double convex lens.

Level - The horizontal openings on a working horizon in a mine; it is customary to work mines from a shaft, establishing levies at regular intervals, generally about 50 metres or more apart.

Lignite - A soft, low-rank, brownish-black coal.

Limestone - A bedded, sedimentary deposit consisting chiefly of calcium carbonate.

Limit order - An order made by a client to a broker to buy or sell shares at a specified price or better.

Limonite - A brown, hydrous iron oxide.

Line cutting - Straight clearings through the bush to permit sightings for geophysical and other surveys.

Lode - A mineral deposit in solid rock.

Logging - The process of recording geological observations of drill core either on paper or on computer disk.

London fix - The twice-daily bidding session held by five dealing companies to set the gold price. There are also daily London fixes to set the prices of other precious metals.

London Metals Exchange - A major bidding market for base metals, which operates daily in London.

Long position - Securities owned outright or carried on margin.

Long ton - 2,240 Ibs. avoirdupois (compared with a short ton, which is 2,000 Ibs.).

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