L

Laboratory

Room or complex containing scientific equipment used for research and tests.

Labradoresce

The present term describing something displaying labradorescence.

Labradorescence

Effect which causes dark, metallic-like color shimmers, commonly blue and green, to be displayed on a few minerals. The name is derived from Labradorite, a mineral which is the best example of this effect.

Laccolith

Lenticular mass of igneous rock stuck between layers of sedimentary rock.

Laminated rock

Sedimentary rocks consisting of many thin layers.

Lanthanides

See rare earth elements

Lapidary

An individual who facets gemstones as a trade, and the shop of such an individual. Also used in adjective form when relating to gems (i.e. lapidary equipment).

Lava

Molten rock on the surface of the earth released from a volcano.

Lenticular

Lens shaped. When applied to minerals it refers to concretions or nodules that have a flattened, lens-like shape

Litmus paper

Paper with powder extracted from certain plants that tests the pH of a substance. Acid turns red while base turns blue; neutral remains white. The stronger the acid or base, the more intense red or blue the color of the litmus paper turns.

Locality

Area where a specific mineral was found or occurs.

Lode

Vein of precious metal.

Longwave

A wavelength of ultraviolet light. Some minerals display fluorescence when exposed to longwave ultraviolet light. (See Fluorescence in mineral properties for more information). See also shortwave. Commonly abbreviated as LW.

Loupe

Small magnifying lens used to observe certain aspects of a gemstone. Loupes usually have a magnification level of 10x.

Lubricant

Material that can reduce friction. Used as a coating on objects that are subject to friction.

Luminesce

To give off light under certain conditions. See luminescence.

Luminescence

General term describing the capability of a mineral with a habit of giving off light when put under certain conditions. Three examples of luminescence are fluorescence, triboluminescence, and thermoluminescence.

Luminescent

General term describing any mineral capable of giving off light when put under certain conditions. Three examples of minerals that are luminescent are minerals that exhibit fluorescence, triboluminescence, and thermoluminescence.

Luster

The exhibition of the surface of minerals, including their reflective properties. (See luster in mineral properties for more information.)