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Emerald

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. To minimise the loss of material, the step-cut (or “emerald-cut”as it is known) is commonly used, but ancient engravings are known, and cameos, intaglios, and beads can make the best of a flawed stone.

Occurrence

Found in granites, pegmatites, and schist’s, as well as alluvial deposits, the finest emeralds are from Colombia. Other sources are Austria, India, Australia, Brazil, South Africa, Egypt, the USA, Norway, Pakistan, and Zimbabwe.

Remark

Most emeralds used in historical jewellery would have been from Cleopatra’s mines in Egypt, which now yield only poor-quality emeralds.

Crystal structure	Hexagonal
Composition	Beryllium aluminium silicate
Hardness	7
SG	2.71
Rl	1.57-1.58
DR	0.006
Lustre	Vitreous