Topaz

Topaz gets its name from the island of Topasos in the Red Sea, or from the Sanskrit word 'tapas' for fire, depending on which source you believe. It is a gem that can be found in a variety of colours from peach, clear and blue, to shades of yellow and pale green. It is a popular gem for jewellery, but is almost always irradiated and then heated to achieve the popular deep blue colours known as London Blue Topaz and Swiss Topaz, although natural pale blue topaz can be found. A peach coloured variety known as Imperial Topaz is the most desired, and a variety known as Mystic Topaz also exists which is colourless Topaz coated with precious metals to form a rainbow coating. A huge cut blue Topaz weighing almost 2 kilograms - 9,381 carats to be precise - is on display in The Natural History Museum in London. The gem was mined in the 1970s in Brazil by Max Ostro, the founder of Ostro Minerals, a topaz specialist. The large blue gem has been treated to achieve the recognisable deep blue colour.