Emerald is the green to bluish green variety of the mineral beryl. Chromium, vanadium or both cause its color.
In more detail
Most emeralds have fractures, and some estimates say 90 percent or more are fracture-filled. Emerald is 7.5 to 8 on the Mohs scale, with fair to good toughness. So cutters often give it a step cut with cropped corners. Heat, steam and ultrasonic cleaners can damage it.
On a grading report
Labs identify it as (natural) beryl, species emerald. The report states any fissure filling, often with its amount: minor, moderate or significant.
Related terms
- Beryl: Beryl is the mineral species of emerald. Aquamarine and the other beryl colors belong to the same species.
- Green beryl: Green beryl is a green beryl that does not qualify as emerald. Its color is too weak, or iron rather than chromium or vanadium mainly causes it.
- Jardin: Jardin, French for garden, is a trade word for the mossy, garden-like inclusions typical of emerald.
- Emerald oiling: Emerald oiling is filling an emerald's fissures with a colorless oil to make them less visible.
- Clarity enhancement: Clarity enhancement is filling surface-reaching fissures with a filler such as oil, resin, wax or glass, so they show less.
- Three-phase inclusion: A three-phase inclusion is a small cavity that holds a liquid, a gas bubble and a crystal. The crystal is often a cube of salt (halite).