mineral
Common Opal
Hydrated amorphous silica (SiO2·nH2O)
AI-generated identification · may be incorrectHardness of 5.5-6.5 on Mohs scale, waxy to vitreous luster, conchoidal fracture, and amorphous crystal structure with no cleavage.
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Physical properties
Hardness of 5.5-6.5 on Mohs scale, waxy to vitreous luster, conchoidal fracture, and amorphous crystal structure with no cleavage.
Formation & geological history
Formed at low temperatures from silica-rich water solutions depositing in fissures of various rock types.
Uses & applications
Used primarily in lapidary arts, ornamental carvings, and mineral collections.
Geological facts
Unlike precious opal, common opal typically lacks play-of-color but displays smooth, milky, or varied pastel tones.
Field identification & locations
Identified by its distinctive conchoidal fracture, waxy luster, and lack of crystalline cleavage planes.
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