Topaz

Topaz is a hard aluminium silicate that forms in large, clean crystals. Most topaz sold is blue, produced by irradiating and heating colourless stones, in shades called sky, Swiss and London blue; it is bright, durable and cheap. Natural imperial topaz, orange to pink from Ouro Preto in Brazil, is a different market: rare, warm and expensive.

How to buy topaz

Blue topaz should be inexpensive; if not, look elsewhere. For imperial topaz, buy stones with a report and a pink to reddish-orange colour. Set with protection because topaz cleaves.

Treatments

Blue topaz is irradiated and heated colourless topaz; the treatment is standard and stable.

Care

Warm soapy water; avoid ultrasonic and knocks, as topaz can cleave.

Lore

Named for an island in the Red Sea; the Portuguese royal family made imperial topaz a symbol of the crown.