gemstone
Opal
Hydrated amorphous silica (SiO2·nH2O)
AI-generated identification · may be incorrectHardness of 5.5-6.5 on the Mohs scale, sub-vitreous to greasy luster, amorphous crystal structure, and a specific gravity around 2.10.
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Physical properties
Hardness of 5.5-6.5 on the Mohs scale, sub-vitreous to greasy luster, amorphous crystal structure, and a specific gravity around 2.10.
Formation & geological history
Forms from a solution of silicon dioxide and water infiltrating cracks in sedimentary or volcanic rock over millions of years.
Uses & applications
Extensively used in high-end jewelry, carvings, and as a prized specimen for mineral collectors.
Geological facts
Opal exhibits a unique optical phenomenon known as play-of-color, caused by the diffraction of light through microscopic silica spheres.
Field identification & locations
Identified by its characteristic iridescence and lack of cleavage; commonly sourced from Australia, Ethiopia, and Mexico.
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