Emerald, the birthstone for May

Emerald is a green to bluish green gem from the mineral family beryl. The birthstone for May, emerald is rarely found without eye visible inclusions. As most emerald material is included, the gem is routinely treated to enhance the apparent clarity by filling cracks and fissures with oil or resin.

There are two schools of thought on what correctly constitutes an emerald, separating it from the less valued green beryl. The first views any green beryl as emerald if its color is caused by chromium. The other school of thought requires emerald to be a gem of sufficiently saturated green color. GIA follows the second school, requiring emerald to be graded against comparison gems to verify that it is dark enough.

Due to it's high value, the manufacturing of emerald is an affordable way of obtaining the look of a gem quality emerald without the cost of the real thing.

Sometimes emeralds exhibit a six-pointed star pattern that is known as a trapiche emerald.

Many famous emeralds exist: the Gachalá, Duke of Devonshire, Bahia, Emerald of Saint Louis, Chalk, and the Mogul Mughal are some of them.

See other gems in the beryl mineral group.

Birthstones and Anniversaries

Emerald is the birthstone for the month of May, and is also the gem of the 20th and 35th anniversaries.

Physical qualities

Chemical Composition: Beryl - Be₃Al₂Si₆O₁₈
Refractive Index: 1.577 to 1.583
Birefringence: 0.005 to 0.009
Specific Gravity: 2.72
Mohs Hardness: 7.5 to 8
Optic Character: Strong dochroism (green and blue green)

Buying Tips

Color: Emerald is most prized when it exhibits vivid color saturation. Colombian emeralds are said to have a more intense, warm, pure green color, while Zambian emeralds are said to lean more to blue greens. This is merely a theory as color does overlap between these sources.
Clarity: Don't expect to find an eye-clean emerald easily. They are exceptionally rare, and are valued accordingly. If you don't care for the heavily included emerals that are standardly available, then consider manufactured emeralds. They offer an affordable way of obtaining the look of a gem quality emerald without the cost of the real thing.

The inclusions may take on a mossy look within the gem. This characteristic is sometimes called jardin which is French for garden.

If you truly want something different look for the rare, trapiche emerald.
Cut: Emerald is a notoriously difficult gem to cut, and harder to cut well. When seeking a significant value emerald, be prepared to be flexible on dimensions or shape. Alternatively be prepared to be patient and wait for the right gem to be found.
Carat Weight: Emeralds are readily available in a wide range of sizes and shapes. Emeralds increase significantly in value as size increases.