G

Gamma rays

Form of electromagnetic radiation which contains the shortest wavelength of the spectrum. Gamma rays easily penetrate matter because of their short wavelength. See also alpha and beta waves.

Gangue material

Worthless material in which valuable metals or gems occur.

Garnet paper

Sandpaper composed of tiny, hard, Garnet crystals, glued on to it for use as an abrasive.

Geiger Counter

Instrument that measures intensity of radiation. It is very useful for detecting radioactive minerals.

Gem

A cut mineral or pearl refined for use as an ornament.

Gemology

The science and procedures involved in mining, faceting, and marketing of gemstones.

Gemologist

Individual practicing in the subject of gemology.

Gemstone

Any mineral or naturally occurring substance in an raw, uncut state that is capable of being a gem.

Geode

Hollow rock that is filled or partially filled with crystals.

Geologic

Having to do with geology.

Geology

The science and study of the physical structure of the earth, including the areas of rocks and minerals.

Gneiss

Banded or layered metamorphic rock, same in composition to Granite.

Glauber's salt

Salt made of sodium sulfate (Na2 SO4 ·10H2O) used in the manufacture of paper ,glass and in stomach medications. Glauber's salt is extracted from the mineral Glauberite.

Globular

The term globular is used as a synonym of botryoidal, but sometimes describes any rounded agglomeration, such as botryoidal, reniform and mammilary.

Goniometer

Instrument that measures crystal angles.

Grain

Individual component belonging to a grainy aggregate.

Grain

Weight used in reference to measuring pearls. A grain is .05 grams or ¼ carat.

Grainy

Crystal aggregate resembling a cluster of grain.

Gram

Weight measurement used to measure less valuable gems or rough stones. It corresponds to the measurement of the metric gram.

Gravel

Accumulation of small, smooth, rounded rock deposited by a stream or river.

Gravity

The force that attracts matter to the center of the earth. The term gravity is sometimes used as a shortened form of the term specific gravity.

Greasy (luster)

Luster of a mineral that appears coated with grease. Some minerals are coated with chemicals to induce a greasy luster.

Group

1) An aggregate of crystals.
2) Synonym of crystal group.
3) The classification order that minerals are arranged in based on their chemical structure.
4) A scientifically recognized selection of minerals similar in structure. All groups have a specific group name, and individual minerals may also be categorized. A mineral in the group may have the same name as group name. An example is the Olivine Group, which contains the minerals Forsterite, Olivine (also known as Chrysolite), and Fayalite. See also series.