The name emerald is also applied to other green minerals that are used as gemstones, such as tourmaline, hiddenite, corundum, and andradite. Beryl crystals are some of the most well-known and prized gems that occur in nature, and include aquamarine, heliodor, and morganite, as well as emerald. Before 1925, gemstones were the primary use for beryl. Since then, beryl has become an important source of the element beryllium, formerly known as glucinium, a metal with a variety of modern commercial uses, particularly in manufacturing metal alloys. The rich green color is created by small amounts of chromium or vanadium imbedded within the crystalline lattice.
Emeralds are notorious for containing flaws, and flawless stones are rare and greatly valued.
The world's finest emeralds originate in the Muzo mining district of Colombia, where most are mined today. Unlike star sapphires, ray patterns in emerald are not caused by light reflections from tiny parallel inclusions, but by black carbon impurities that happen to form in the same pattern. Emeralds have also been found in Australia, the Urals, Norway, Austria, and North Carolina. In the ancient Old World, emeralds were mined primarily in Egypt. Synthetic emeralds have been produced successfully since the mid-1930s.