emerald

Grass-green variety of beryl that is highly valued as a gemstone. Its physical properties are those of beryl. Its refractive and dispersive powers (i.e., its capacity to deflect light and to break white light into its component colours) are not high, so cut stones display little brilliancy or fire (flashes of colour). The colour that gives this gem its value is due to the presence of small amounts of chromium. The most important production of fine quality gem material is from Colombia; emeralds are also mined in Russia, Australia, South Africa, and Zimbabwe. Synthetic emeralds are identical to natural crystals and may rival them in colour and beauty.