EMERALD

This mineral occurs as prismatic crystals, which are sometimes terminated with small pyramids. It forms in pegmatites and granites and in some regionally metamorphosed rocks. Emerald derives its beautiful green colour from the presence of chromium and vanadium. Emeralds are rarely flawless, so stones are often oiled to fill and disguise cracks, hide flaws and enhance colour. Snippet: Most emeralds used in historical jewellery would have been from Cleopatra's mines in Egypt, which now yield only poor-quality emeralds.

Hardness: 7 1/2

Other characteristics:-

The mineral beryl and the gemstone emerald.