Cliché Columbian Emerald Ring

Emerald is beryl coloured green: the same mineral as aquamarine and morganite, a silicate of beryllium and aluminium, given its green by traces of chromium and vanadium. It is hard, 7.5 to 8 on the Mohs scale, but brittle, and almost never clean. The inclusions inside are called its jardin, its garden, and are expected rather than hidden. Nearly every emerald is oiled to settle the fine fissures that reach its surface, a practice centuries old, which is why the treatment is always declared.

The first known emerald mines were in Egypt's Eastern Desert, worked under the Ptolemies and the Romans. Everything changed in the sixteenth century, when the Spanish reached the mines of the Colombian Andes, already old by then. Colombian emeralds went on to the treasuries of Spain, the Ottoman sultans and the Mughal emperors, who had some of the largest carved with prayers.

Emerald is found in Colombia, the classic source, and in Zambia, Brazil, Ethiopia, Zimbabwe and Afghanistan's Panjshir valley, each a slightly different green: Zambian emeralds, with more iron, lean blue.

Colombia's emeralds come from the Eastern Cordillera of the Andes, north of Bogotá, from the mines of Muzo, Coscuez and Chivor in Boyacá. They formed differently from almost every other emerald, from hot, salty fluids moving through black shale rather than from molten rock. That leaves little iron to dull the colour, which is why Colombian green is so warm and pure, and it leaves a signature inside: tiny pockets holding a liquid, a bubble of gas and a grain of salt at once. The mines were already old when the Spanish reached them in the sixteenth century.

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Take it off for the gym, the sea and the garden. Warm water, a drop of soap and a soft brush; dry with a soft cloth.