Colour: Can be found in many shades of green, the better stones should be a deeper colour. (Colour of Crème De Menthe.)
Hardness: 7½ (on Moh’s hardness scale.)
Specific Gravity: 2.71. This is an indication of the stone's density, calculated by comparing the stone's weight with the weight of an equal volume of water.
Refractive Index: 1.57 to 1.58. This is a measure of the amount light is bent from its original path when passing through a stone.
Chemical composition: Beryllium aluminium silicate. Part of the Beryl family of minerals.
Principal sources: Colombia, Austria, India, Australia, Brazil and South Africa.