All About Emerald
Emerald is the green variety of Beryl, it is the most famous and valuable green gemstone. It is one of the most expensive gemstones due to the fact of its green colour, combined with durability and rarity. A deep green colour is the most desired colour in Emeralds. The more pale an Emerald is in colour the lesser its value. Very pale Emeralds are not called Emeralds but rather Green Beryl. Emeralds are occasionally heat treated causing their colour to turn blue and transform into Aquamarine.
Emerald is one of the gem varieties of the mineral Beryl, which also includes blue Aquamarine, pink Morganite, and yellow Heliodor/Golden Beryl, Pure Beryl. The green colour of Emerald is usually caused by chromium impurities, and occasionally by vanadium impurities.
Emerald is notorious for its flaws. Flawless stones are very uncommon, and are noted for their great value. Some actually prefer Emeralds with minute flaws over flawless Emeralds, as this proves authenticity. Flaws are often hidden by treating the Emeralds with oil or synthetic lubricants. Although Colombian Emeralds have been traditionally the highest quality Emerald with the finest green colour, a new source of Emeralds from Zambia have emeralds which are deep green with fewer flaws.
A rare and unusual form of Emerald , known as “Traphiche Emerald” is characterized by star-shaped rays that emanate from the centre of a stone in a hexagonal pattern. The rays are similar to asterism, but are not caused by light reflection from tiny parallel inclusions. The rays are produced by black carbon impurities that form in a star-shaped pattern. These are only found in Boyaca Emerald mining district of Colombia, and are cut into cabochons.
Although Emeralds have good hardness, they are brittle stones. It may develop internal cracks if banged hard or exposed to extreme temperature change. Emeralds that are treated for internal flaws should not be cleaned using ultrasonic jewellery cleaner or washed with soap as they remove the oil treatment and expose internal flaws.
Types of Emerald
|Cat's Eye Emerald|
False Named Emerald
Emerald have been synthetically made since 1848. Synthetic Emeralds can be similar to natural Emerald which would make it hard to distinguish the difference by normal procedures. Here is a list of synthetic Emeralds that you should watch out for.
Treatments and Enhancements Performed on Emerald
Emerald flaws are very often concealed by treating a stone with oil or synthetic lubricants. This is common practice in the gemstone industry. Since the fracture filling material have similar refractive indices to emerald, it optically hides the underlying flaws. Oiling is performed by heating the emerald in a cylinder containing oil. This allows the oil to penetrate the stone. The oil most commonly used is cedar oil. A more effective fracture filling procedure is known as irradiation. When looking to purchase an emerald always check to see if they are fractured filled as it will affect the pricing of the emerald. If it is not specified as not fracture filled, it is safe to assume it is. The oiling procedure does not last forever, and frequent cleaning will hasten this process.
Stones Similar to Emerald
Green is usually darker green in colour, and Chrome Diopside is much softer. Tsavorite can be confused with Emerald, but its optical properties differ.