gemstone
Opal
Hydrated amorphous silica, SiO2·nH2O
AI-generated identification · may be incorrectHardness of 5.5 to 6.5 on the Mohs scale, subvitreous to greasy luster, amorphous crystal structure with no cleavage, and specific gravity around 2.10.
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Physical properties
Hardness of 5.5 to 6.5 on the Mohs scale, subvitreous to greasy luster, amorphous crystal structure with no cleavage, and specific gravity around 2.10.
Formation & geological history
Formed from a solution of silicon dioxide and water seeping into cracks and voids in sedimentary or volcanic rock, typically over millions of years.
Uses & applications
Extensively used in high-end fine jewelry, such as rings, pendants, and earrings, as well as highly prized by mineral and gemstone collectors.
Geological facts
Opal displays a unique optical phenomenon known as play-of-color, caused by the diffraction of light through microscopic silica spheres within its structure.
Field identification & locations
Easily identified by its characteristic milky or transparent body tone combined with flashes of spectral colors; predominantly sourced from mines in Australia.
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