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Lamprophyre

An igneous sedimentary rock, composed of altered mafic and ultramafic minerals

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Lamellar

A term used to describe the arrangement of leaves or sheets in a structure, sometimes bound on a side

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Lagging

Planks, rods, beams or timbers used to between steel ribbing of an underground structure to fortify support and prevent the picture or rupture of a roof and overlying rocks

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Lactic acid

A chemical agent sometimes used in the process flotation to depress iron minerals

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Laccolith

A formation where pressurized volcanic fluid beneath the Earth’s surface pushes the overlying rock into a dome shaped structure

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Lava tube

A hollow cylinder or tube like underground formation of solid lava

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Lava bomb

A volcanic bomb is a chunk of ejected viscous lava larger than a lapilli, being over 64 mm.

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Lava

Molten volcanic rock, still in a hot viscous state and not yet solid

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Lapis lazuli

A blue semi precious stone, frequently used in jewelry for at least 3,500 years