A gemstone, pearl or organic or non-organic substance that has intrinsic value based on its rarity, quality, size, durability, and beauty, but apart from any setting, and usually based on appliedworkmanship, as the quality of the cutting of a gemstone or the carving of a piece of hardstone, coral, amber, ivory or jet used as jewelry.The term 'gem' was originally applied to a gemstone decorated with carving or engraving, but since the last century it has been extended to any gemstone of quality, usually one that has beenfaceted, but exclusive of synthetic gemstones and glass.
Gem

Gem
A gemstone, pearl or organic or non-organic substance that has intrinsic value based on its rarity, quality, size, durability, and beauty, but apart from any setting, and usually based on appliedworkmanship, as the quality of the cutting of a gemstone or the carving of a piece of hardstone, coral, amber, ivory or jet used as jewelry.The term 'gem' was originally applied to a gemstone decorated with carving or engraving, but since the last century it has been extended to any gemstone of quality, usually one that has beenfaceted, but exclusive of synthetic gemstones and glass.
References
From: An Illustrated Dictionary of Jewelry, autor: Harold Newman, publishers: Thames and Hudson



