"Emerald is a green variation of the mineral beryl that has been highly valued as a gemstone for thousands of years. Scholars speculate that the name derives from the Greek word smaragdos, a term that was also used when referring to other green-colored stones. 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 crystal structure of beryl emeralds is hexagonal (six-sided) with a hardness slightly higher than quartz but considerably less than that of diamond. 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."
