or hard material that can be cut
, and used in jewelry
. Also called gem
Gemstones are evaluated using four major criteria: beauty, rarity, durability, and desirability. A valuable gemstone must be pretty, not too common, hold up under wear, and be of good quality. (See what attributes make a gemstone desirable?.)
Gemstones are sometimes divided into the categories of precious stones (diamond, emerald, ruby and sapphire; sometimes also pearl) and semiprecious stones (anything that isn't precious but is capable of jewelry use). Nonprecious stones wouldn't be considered gemstones.
Durability: Mohs hardness scale, tenacity, cleavage
Weight: Carat (not karat), point, grain
Cut: Facet, Cabochon, Lapidary
Gem phenomena: Adularescence, Asterism, Aventurescence, Chatoyancy, Color change, Color play, Color zoning, Fluorescence, Iridescence, Pleochroism.
Other: Gem enhancement, Synthetic gems, Simulant (Cubic zirconia)