Emerald

Emerald is beryl coloured by chromium or vanadium. Colombian stones set the standard for a warm, slightly bluish green; Zambian stones are slightly bluer, cleaner and better value. Inclusions, called the garden, are expected; nearly all stones are treated with oil or resin to reduce their visibility, and the degree of treatment moves the price more than anything except colour.

How to buy emerald

Buy for colour and for minor treatment only, stated on a report. Choose a protective setting, bezel or halo, and accept that an emerald is an occasional ring, not a gym ring.

Treatments

Oiling or resin filling of fractures is standard; the degree (none, minor, moderate, significant) is stated on reports.

Care

Damp cloth only. Never ultrasonic, steam, hot water or solvents; they strip the oil and can crack the stone.

Lore

Cleopatra claimed Egypt’s emerald mines for herself; Spanish conquistadors shipped Colombian emeralds to the courts of Europe and India.