Zircon & Tourmaline

Zircon: Comes in a wide array of colours from the colourless (Heated) through Sky Blue (also heated) to yellow, golden brown, red, orange and intermediate ranges of these colours.
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Zircon is a silicate of zirconium and as a cut stone has a brilliance and lustre close to that of diamonds so much so that it could easily fool one, especially when mounted. It is also a brittle stone and is preferably stored in such a way as to prevent them rubbing against each other to avoid what is known as “paper wear”.
The brownish Zircons can be heated in an oxidizing atmosphere to produce the brilliant white stones and in a reducing atmosphere to produce the sky blue stones. These heated stones, with the passage of time and exposure to sunlight for long periods (say 5 years) can revert to their original colours but can be re-heated to produce the original colour.

Zircon is a radioactive stone and consists of three main types; the high, medium low, the high type undergoing decomposition due to radiation , the medium type being already partially decomposed and the low type having undergone almost complete decomposition.

Certain varieties of zircon when heated and cut en-cabochon show a cats-eye effect and when these stones are honey coloured can often be mistaken for chrysoberyl cats-eyes.

Zircon is found abundantly in the gem gravels of Sri Lanka along with other gems, it is also found in Thailand, Madagascar, Tanzania and Australia while a red zircon is found in France.

Tourmaline: This gem is rarely if ever surpassed in the range of colours it exhibits. From beautiful reds and pinks to emerald greens and all the colours in between like yellow, blue and to that of the recently discovered Paraiba tourmaline which is an electric blue with a high degree of lustre whose prices sometimes even surpasses that of medium quality blue sapphires and rubies. Tourmaline is found as colourless crystals and as totally opaque black crystals.

Tourmaline shows the rather unusual phenomenon of pyroelectricity which is the development of positive and negative charges on opposite ends of the crystal when heated to about 1000 degress C. Tourmaline crystals also develop an electric charge called piezoelectricity when pressure is applied in the direction of the vertical crystal axis These properties have various applications in science and industry.

Green tourmaline (amongst other colours) is found in Russia (Urals), Brazil, Sri Lanka, Madagascar, India, Afganhistan, Pakistan, Burma,