mineral
Opal
Hydrated amorphous silica (SiO2·nH2O)
AI-generated identification · may be incorrectHardness of 5.5-6.5 on the Mohs scale, vitreous to sub-vitreous luster, amorphous crystal structure, and exhibits a unique play-of-color due to the diffraction of light.
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Physical properties
Hardness of 5.5-6.5 on the Mohs scale, vitreous to sub-vitreous luster, amorphous crystal structure, and exhibits a unique play-of-color due to the diffraction of light.
Formation & geological history
Formed from a solution of silica and water, typically deposited in cavities of sedimentary or volcanic rocks at low temperatures.
Uses & applications
Primarily used in high-end jewelry, as a gemstone, and prized by mineral collectors.
Geological facts
Opal contains up to 20% water and can dry out and craze if exposed to extreme heat or low humidity.
Field identification & locations
Easily identified by its characteristic opalescence and internal flash of spectral colors. Found extensively in Australia, Ethiopia, and Mexico.
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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