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Identification
A gemstone is a mineral or organic material that can be cut and polished for use in jewelry, ornamentation or objects of art. Natural gemstones are found mostly in igneous rocks and alluvial gravels, although some have been found in sedimentary and metamorphic rocks.
Features
Natural gemstones have two major characteristics: hardness and specific gravity. Hardness relates to how resistant a gemstone is to scratching. Specific gravity is the ratio of density between a gemstone and an equal amount of water.
Types
Diamond, emerald, aquamarine, topaz, opal, ruby and sapphire are classified as precious gemstones. Those that possess lesser qualities are considered semi-precious. Organic non-mineral gemstones include amber, fossil, coral, pearl, ivory and jet.
Geography
Natural gemstone formations occur in most geologic terrains, with the type of stone depending on environmental characteristics. Gemstone deposits are found all over the United States, but larger deposits of the most precious kind come from outside the country. Diamonds come mostly from Africa, Siberia and western Australia.
Warning
Synthetic gems and inferior cuts or grades of natural gems are increasingly being sold to inexperienced buyers. A buyer should take care when purchasing gems to ensure they come from natural sources and are of high quality.