mineral
Common Opal
Hydrated amorphous silica (SiO2·nH2O)
AI-generated identification · may be incorrectHardness of 5.5-6.5 on the Mohs scale, waxy to vitreous luster, white to cream color, and conchoidal fracture.
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Physical properties
Hardness of 5.5-6.5 on the Mohs scale, waxy to vitreous luster, white to cream color, and conchoidal fracture.
Formation & geological history
Formed at low temperatures from silica-rich water solutions depositing in crevices of various rock types.
Uses & applications
Used primarily in lapidary arts, ornamental carvings, and as a mineral specimen for collectors.
Geological facts
Unlike precious opal, common opal lacks the characteristic play-of-color due to its non-ordered internal sphere structure.
Field identification & locations
Identify by its characteristic conchoidal fracture, waxy luster, and lack of cleavage; found worldwide in volcanic and sedimentary environments.
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Other mineral specimens
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Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Tumbled granite
Granite, a coarse-grained felsic intrusive igneous rock
igneous
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Granite
Granite (Phaneritic intrusive igneous rock)
igneous