Gemstones

Gems are mineral crystals that have been cut and polished. Jewelers, for example, may select certain crystals to cut into gems because of their extraordinary color, but select others such as diamonds for their hardness and flashes of color. Although almost any of the four thousand kinds of minerals could be cut into a gemstone, in practice most gems used in jewelry today come from only about fifteen different minerals. Size, beauty, rarity, and durability are the basic criteria that determine a gem's value. Because of their beauty and the skill and artistry necessary to cut gemstones from crystals, gems have always been expensive and a representation of wealth and power. For centuries, gems belonged almost exclusively to royalty. One factor in the value of a gem is its weight. Gem weight is measured in carats; one metric carat equals 0.2 grams (.007 ounces). The word carat comes from carob, a Mediterranean tree whose seed was for centuries the standard for weighing precious stones.

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