Emerald means ‘green gemstone’. It is a variety of the mineral beryl (Be3Al2(SiO3)6)
colored green by trace amounts of chromium and sometimes vanadium. Emeralds are fascinating gemstones. They have the most beautiful, most intense and most radiant green color, the emerald green.
Emeralds occur in hues ranging from yellow-green to blue-green, with the primary hue being green. Yellow and blue are the normal secondary hues found in emeralds. Only gems that are medium to dark in tone are considered emerald; light-toned gems are known instead by the species name green beryl.
Most emeralds are oiled, often with Cedar oil, to improve their clarity and stability. The use of oil is largely accepted in trade; although oil treated emeralds are much less expensive than untreated emeralds of similar quality. So disclosure is required when these are sold in the market.
Other treatments, like use of green-tinted oil, are not acceptable in the trade. Emeralds are occasionally color-enhanced by introducing dye into surface reaching fissures to deepen the green color of less valuable lighter Emeralds.
Synthetic Emeralds are created by Hydrothermal synthesis and the flux growth synthesis.
Chromium, vanadium, and iron are the trace elements that make emerald’s color. The presence or absence of each and their relative amounts decide the exact color of an emerald crystal. The most desirable emerald colors are bluish green to pure green, with vibrant color saturation and tone that’s not too dark. The most-prized emeralds are highly transparent. Their color is uniformly distributed, with no eye-visible color zoning. If the hue is too yellowish or too bluish, the stone is not emerald, but a different variety of beryl.
Columbian emeralds are mined in Columbia and are known for their exceptional quality. These are the most expensive type followed by Brazilian and Zambian emeralds.
Brazilian emeralds are lighter green gemstones that are mined in Brazil. Cat’s Eye Emeralds have a cat’s eye effect, called a chatoyancy, which looks like a wide slit similar to the pupil in a cat’s eye. These are very rare and only found in paler green emeralds.
Trapiche emeralds contain certain black impurities that form a six-rayed star. This unusual type of emerald is mined only in the Muzo area of Columbia. The term “star emeralds” typically refers to trapiche emeralds. The term is sometimes used to describe the atypical occurrence of asterism, or a rayed star moving inside of an emerald.