Afghan aquamarine

Afghan aquamarine is the blue beryl of the granite pegmatites of eastern Afghanistan. It has been dug at Gur Salak in Kunar since the mid 1980s, it comes out of the Pech valley fields over the provincial line from Nuristan, and it grows with the kunzite in the Mawi and Kolum workings of Nuristan's Du Ab. It is sold as Afghan or Kunar aquamarine, and often under the Nuristan name, in pale to medium blue with a green cast in most of the rough. The largest Afghan aquamarine on record, a cat's-eye of 586 carats from the Pech valley, is in the Smithsonian.

This page is written from Nuristan, where aquamarine still sits in the rock of the Sewketra valley in Waygal, in a field nobody has yet worked. It says where the stone comes from, which colours are worth paying for, what it sells for with the source of every figure, how it is heated and why nobody can see it, what a laboratory can and cannot tell you, and what to ask a seller. The province's stones as a whole are on the Nuristan gemstones page, and the law for buyers is on its own page.

Colour first: the deeper and purer the blue, the higher the price, and green or grey pulls it down. Then size, the opposite way round from most stones: small aquamarines are rarely saturated enough to show well, so a fine five carat stone is worth more a carat than a fine one carat stone, and the per-carat price only falls again above about 25 carats, where a stone becomes hard to set. Clarity is expected. Aquamarine grows clean, most faceted stones are eye-clean, and visible inclusions send a stone to the cabochon cutter unless they make a cat's-eye. Cut matters because the stone is pleochroic, near-colourless in one direction and blue in another, so the cutter keeps the table parallel to the length of the crystal to hold the blue.

Afghan material has a name for clarity. The British Geological Survey calls the Gur Salak crystals often of very clear gem quality, Bowersox illustrated a 75.8 carat faceted stone beside a 5.7 centimetre crystal cluster in 1985, and the 586 carat cat's-eye was cut from a single crystal. The weakness is colour: much of it is pale, and the dark blues are the exception and are priced as one.

Nearly all aquamarine is heated. Most crystals come out of the ground greenish blue, and heating to about 375 degrees in an oxygen-free kiln turns the iron that gives the green into the iron that gives the blue. The change is permanent and cannot be detected by any laboratory, so the trade's rule is that a pure blue aquamarine is probably heated, and a gem report says so. Some stones keep a green cast after several cycles, and overheating discolours them. Nothing in the Afghan trade is different: assume heating unless the seller states otherwise in writing, and remember that an honestly unheated greenish stone is the rarer thing.

Irradiation makes a deep blue beryl, the Maxixe type, from pale or colourless material, and it fades in daylight. The trade does not accept it and it is uncommon, and a gemmologist can catch it because it shows the same blue from every direction where true aquamarine shows blue one way and near-colourless the other. Fracture filling with resin is rare in aquamarine and must be disclosed. Dyeing and coating are not practices documented for Afghan stones.

Buy the colour, not the origin. Judge the blue in daylight and in shade, ask whether the stone is heated and get the answer in writing, and for anything over a few hundred dollars ask for an identification report, which costs from about 75 US dollars at GIA. Synthetic aquamarine is grown in the laboratory but is uncommon in the trade; the usual substitutes are blue topaz, which is heavier for its size, synthetic spinel and glass, and a report rules all of them out. For rough, see the pieces in daylight with the weights, and remember that the dark end of a parcel is what sets its price.

Our guide to buying gemstones from Afghanistan covers the law for buyers in the United Kingdom, the European Union and the United States, the import duties, the laboratories and their fees, and the fakes that have been documented. If you want aquamarine from Afghanistan, write to us and tell us what you are looking for: cut stones, facet rough by the gram or the lot, or crystals and specimens. We source at first hand from the people who mine or find the stones, in Nuristan and in Kunar, and we will say honestly what we can and cannot do.