The name emerald means “green gem”. It is an ancient Greek word. The reason its green in color is because of traces of chromium and vanadium in the stone. Emerald is also known as a Beryl.
Gemstones are graded by color, cut, clarity and carat weight. Color is the most important aspect of a stone’s grade is color. But when it comes to grading emeralds, clarity is just as important. In emeralds, they must be a pure green and have a high degree of transparency.
When grading the color of a gemstone, it must have three components: tone, saturation and hue. Emeralds can have a yellow-green to blue-green hues. But green must be the most dominate color in the stone.
Only emeralds that are a medium to dark green are considered true emeralds. Lighter toned stones are considered green beryl. The hue of an emerald should be bright, not dull.
Emerald comes from the beryl family which includes blue aquamarine, yellow heliodor, pink morganite, red beryl and bixbite.
Emeralds are graded by the eye, not a magnification like diamonds. Almost all emeralds are oiled to enhance apparent clarity. The most valuable emeralds are clean, have a vivid green hue and a medium to dark tone. Most emeralds are cut in an oval or emerald cut.
The reason emeralds are oiled is because it improves their clarity and stability and fills in any cracks it may have. Cedar oil is used to do this, but synthetic oils can also be used. This is done in a vacuum chamber under mild heat to open the pores of the stone and allow the oil to fill in the fractures and be absorbed. The U.S. Federal Trade Commission requires that it be disclosed when this treatment is done. The use of oil is accepted by the gem trade, but untreated emeralds are worth much more. The use of tinted oil to enhance the color is not acceptable.
Emerald is the May birthstone and the astrological sign for Taurus, Gemini and sometimes Cancer.
The goddess Minakshi at India’s most famous temple (Madurai Minakshiamman) is carved out of a single of emerald stone.