mineral
Opal
Hydrated amorphous silica (SiO2·nH2O)
AI-generated identification · may be incorrectHardness of 5.5-6.5 on the Mohs scale, varying body colors often with play-of-color, subvitreous to pearly luster, and amorphous crystal structure with no cleavage.
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Physical properties
Hardness of 5.5-6.5 on the Mohs scale, varying body colors often with play-of-color, subvitreous to pearly luster, and amorphous crystal structure with no cleavage.
Formation & geological history
Formed from a solution of silica and water seeping into cracks and voids in sedimentary or volcanic rock over millions of years.
Uses & applications
Extensively used in high-end jewelry, carved ornaments, and sought after as a prized collector specimen.
Geological facts
Precious opal diffracts light due to its internal microscopic silica spheres, creating its signature rainbow flash.
Field identification & locations
Identified by its characteristic conchoidal fracture, lack of crystalline structure, and potential play-of-color; commonly sourced from Australia and Ethiopia.
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Other mineral specimens
Gneiss or Schist
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