Hardness

Hardness refers to the amount of resistance a gem has to scratching and abrading. Gems receive a hardness rating between one, the softest, and 10, the hardest.

Imitation

Gems that have only a visual similarity to natural gemstones. Imitation gems are entirely manmade. Also called Simulated.

Inclusion

Flaws inside of a gem.

Karat

Karat, or K, refers to the percentage of gold in jewelry. Items labeled 18K, 14K, or 10K contain gold mixed with another metal, and items falling below 10K cannot be called gold. 24K indicates 100 percent gold; also referred to as solid gold. 18K indicates 75 percent gold. 14K indicates 58.3 percent gold. 10K indicates 41.7 percent gold.

Lab-Grown or Lab-Created

Gems grown in a lab that have chemical and optical properties essentially the same as, but not identical to, natural gems.

Loupe

A small, hand-held magnifying glass that is held up to the eye and provides 10-times magnification.

Luster

A bright shine showing on the surface of gems or metal.

MOHS Rating

The number between one and 10 assigned to a gem according to its scratch resistance. See Hardness.

Mother-of-Pearl

A hard, pearly lining from certain mollusks’ shells. Two common mollusks with this smooth lining are pearl oysters and abalone.

Natural

Gems mined from the earth; also called Genuine.

Nickel Silver or German Silver

An alloy combining copper, nickel, and zinc that does not contain actual silver.