mineral
Common Opal
SiO2·nH2O (Hydrated Silica)
AI-generated identification · may be incorrectHardness of 5.5-6.5 on the Mohs scale, milky white to translucent color, vitreous to waxy luster, and amorphous crystal structure with no cleavage.
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Physical properties
Hardness of 5.5-6.5 on the Mohs scale, milky white to translucent color, vitreous to waxy luster, and amorphous crystal structure with no cleavage.
Formation & geological history
Formed at low temperatures from silica-rich water solutions deposited in cavities of various rock types.
Uses & applications
Used primarily for ornamental items, carving, and as a collector mineral specimen.
Geological facts
Unlike precious opal, common opal lacks the characteristic play-of-color due to its lack of an orderly microscopic sphere arrangement.
Field identification & locations
Identified by its conchoidal fracture, waxy luster, and lack of crystalline cleavage; found globally including Australia, Mexico, and the USA.
