Colour: Milky or grey background with flashes of colours; orange, red, green, blue. Fire Opal is bright orange.
Hardness: 6 (as per Mohs hardness scale)
Sources: Mainly from Australia but also from USA, Brazil, Mexico
Interesting Facts: Mainly cut as cabochon stones, opal are formed from silica gel. It can occur as stalactites or stalagmites and can sometimes be found in fossil wood or shell, or filling a cavity in a sedimentary rock.
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