The gemstone emerald

Emerald, the green variety of the mineral beryl, is the most famous and favored green gemstone. Its beautiful green color, combined with durability and rarity, make it one of the most valuable gemstones. Beryl also contains other, lesser known gem varieties, such as aquamarine and heliodor. Pure beryl is white; emerald's green color is caused by chromium impurities (and occasionally by vanadium impurities). Deep green is the most desired color in emeralds. The paler the color of the emerald, the lesser its value. Pale emeralds are not called emeralds, but "green beryl". They are sometimes heat-treated, in which they become aquamarine.

Emeralds are notorious for their flaws. Flawless stones are very uncommon, and are noted for their great value. Some people actually prefer an emerald with very minute flaws over a flawless emerald, as this proves authenticity of the stone. Many emerald flaws can be hidden by treating the emeralds with oil. Newer, more effective fracture-filling techniques are also practiced. Irradiation of some emerald gems is somewhat effective in removing certain flaws.

Many emerald fakes and doublets are known. Two pale colored stones may be glued together with a deep green paste, creating a stone resembling emerald. Faceted green glass also resembles emerald, and it may be coated with a hard substance to mask its low hardness. Synthetic emeralds are also sold to unwary buyers without them knowing the stone is synthetic. Experts can distinguish all these fakes, and it is especially important to only purchase emeralds from reliable dealers. Experts can also determine if an emerald was treated with oil to mask internal flaws. Generally, unless otherwise specified, it can be assumed that an emerald has been treated with oil.

A rare, prized form of emerald, found only in the Muzo mining district of Colombia, is a very unusual form of this gem. This emerald, known as "Trapiche emerald" is characterized by star-shaped rays that emanate from its center in a hexagonal pattern. These rays appear much like asterism, but, unlike asterism, they are not caused by light reflection from tiny parallel inclusions, but by black carbon impurities that happen to form in the same pattern.

Emerald may develop internal cracks if banged hard or if subject to extreme temperature change. Emeralds that were treated to mask internal flaws should never be cleaned with an ultrasonic jewelry cleaner, nor should they be washed with soap. These practices will remove the oil and expose the hidden internal flaws.

USES
Transparent emeralds are faceted in gem cuts for jewelry, and translucent material is cut and polished into cabochons and beads. Trapiche emeralds are also cut into cabochons, making exquisite jewelry pieces. A very small number of emeralds display asterism and chatoyancy; these too are cut into cabochons.
Emerald is very sensitive to knocks, and the famous emerald cut was developed specifically for this gem to reduce the amount of pressure during cutting.

Emerald is the birthstone of May.

VARIETIES

Colombian Emerald - Emerald from Colombia. This emerald is usually of exceptional quality.

Brazilian Emerald - Emerald from Brazil. The Brazilian emeralds are generally a lighter color than the Colombian emeralds. (The term Brazilian Emerald may also refer to green Tourmaline from Brazil.)

Zambian Emerald - Quality emerald from Zambia

Trapiche Emerald - Emerald with black impurities in the form of a six-rayed star

Star Emerald - Usually refers to trapiche emerald (above), but may also correctly refer to the rare occurrence of an emerald displaying asterism

Cat's Eye Emerald - Emerald exhibiting cat's eye effect. Cat's eye emerald is very rare, and only exists on paler emeralds.

FALSE NAMES
Emeralds have been synthetically produced since 1848. However, only recently have synthetic emeralds been available of the market. The synthetic emeralds currently produced are so similar to true, natural emeralds that they are virtually indistinguishable by normal means. Here are some names for synthetic emerald to watch out for:

Biron Emerald

Chatham Emerald

Gilson Emerald

Kimberly Emerald

Lennix Emerald

Linde Emerald

Regency Emerald

Zerfass Emerald

Glass dyed green is also a major emerald simulator. The color of green glass and emerald may be identical, but other physical and optical properties can easily differentiate the two. Some fraudulent names given to green glass used as jewelry:

Broghton Emerald

Endura Emerald

Ferrer's Emerald

Medina Emerald

Mount St. Helens Emerald

Spanish Emerald

Other false emerald names include:

African Emerald - green fluorite

Bohemian Emerald - green fluorite

Cape Emerald - prehnite

Congo Emerald - dioptase

Emeraldine - chalcedony dyed green

Emeraldite - green tourmaline

Evening Emerald - peridot

Indian Emerald - quartz or chalcedony dyed green

Lithia Emerald - hiddenite

Mascot Emerald - emerald doublet

Night Emerald - peridot

Oriental Emerald - green sapphire

South African Emerald - green fluorite

Tecla Emerald - emerald doublet

Traansvaal Emerald - green fluorite

Uralian Emerald - demantoid garnet

SIMILAR GEMSTONES
Green sapphire may resemble emerald, but its high hardness distinguishes it. Garnet and zircon rarely achieve a deep green like emerald, and diopside and dioptase are considerably softer than emerald. Green tourmaline can only be distinguished by its difference in optical properties.

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ALSO SEE
The mineral Beryl
The gemstone Beryl
The gemstone Aquamarine

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