Tuesday, 3 May 2011

Opal ~

Opal is a fragile gem: it contains a large amount of water and is sensitive to dehydration which may cause cracking; it also scratches easily, so needs to be handled and stored with care.

The specimen shown here is 'boulder opal' in which the opal typically occurs in what appears to be brown rock. 

Wikipedia states that:
Opal is an amorphous form of silica related to quartz, a mineraloid form, not a mineral. 3% to 21% of the total weight is water, but the content is usually between 6% to 10%. 

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