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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, com posed of dark minerals, that occurs in dykes; sometimes contains diamonds.
- Laterite - A residual soil, usually found in tropical countries, out of which the silica has been leached. May form orebodies of iron, nickel, bauxite and manganese.
- Launder - 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 contaitied 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 levels at regular intervals, generally about 50 meters 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.
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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 bid ding market for base metals, which operates daily in London.
- Long position - Securities owned out right or carried on margin.
- Long ton - 2,240 lbs. avoirdupois (compared with a short ton, which is 2,000 lbs.).
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