[Jewelry making - Article 00970] - Re: [Orchid] White sapphire value

[leonid surpin]

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Bill,

    the reason there are no unburned white sapphires (burning is what
    we here call heat treatment ) because there are no reason to burn
    them. 

    Sapphire is heat treated to improve it's colour. Sapphire gets its
    blue colour from Titanium Oxide (TiO2). Often, during crystallization
    phase Titanium Oxide exsolves and forms what is called silk. If there
    is too much of it, we have what is called geuda sapphire. During heat
    treating such a sapphire Titanium Oxide dissolves back into crystal (
    plainly speaking, the actual mechanics more involved ) and that what
    makes sapphire blue. If sapphire is white ( colorless ) you can heat
    it until cows come home and nothing will change. That is why there is
    no "unburned whites". 

    As far as value of white sapphire, the only value is in labor
    involve in cutting the stone. Colourless sapphire is simply an 
Alumina
    (Al2O3) very plentiful material and very inexpensive. 

Leonid Surpin.
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