mineraloid
Common Opal
SiO2·nH2O
AI-generated identification · may be incorrectHardness of 5.5-6.5 on the Mohs scale, waxy to vitreous luster, amorphous crystal structure, and conchoidal fracture.
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Physical properties
Hardness of 5.5-6.5 on the Mohs scale, waxy to vitreous luster, amorphous crystal structure, and conchoidal fracture.
Formation & geological history
Formed from the precipitation of silica-rich water in fissures and cavities of various rock types, often volcanic.
Uses & applications
Used primarily as a gemstone in jewelry and valued as a collectible mineral specimen.
Geological facts
Unlike precious opal, common opal typically lacks play-of-color and is often found in milky green, brown, or yellow hues.
Field identification & locations
Identify by its conchoidal fracture, waxy luster, and lack of cleavage, commonly found in regions with past volcanic activity.
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