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About Opal and Types of Opal

About Opal and Types

Opal is a form of hydrated silica (silicon dioxide, which has a variable amount of water in the formula). Opal may consist of 3% to 21% of it’s weight, as water.


Unlike other forms of silica, opal is amorphous (lacking crystalline structure) and is therefore considered a mineraloid, rather than a mineral.


Opal is usually located in areas consisting of geology of either sandstone, basalt,limoniterhyolite or marl.


Australia produces more than 95% of the opal in the World.


Black Opal is the most valuable and sought after opal and derives it's name from the background color or the color of the back of the opal. Black opal contains carbon and iron oxide trace elements, which give it the dark appearance and

The darker, or more black the background the more valuable to stone may be.



Crystal opal is translucent when held up to the light and is found at Lightning Ridge and Coober Pedy in SA.



Comes from ironstone and is mined in Queensland.



Found at Coober Pedy in South Australia. White Opal also produces crystal opal.