gemstone
Opal
Hydrated amorphous silica (SiO2·nH2O)
AI-generated identification · may be incorrectHardness of 5.5 to 6.5 on the Mohs scale, vitreous to sub-resinous luster, and amorphous crystal structure with no cleavage.
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Physical properties
Hardness of 5.5 to 6.5 on the Mohs scale, vitreous to sub-resinous luster, and amorphous crystal structure with no cleavage.
Formation & geological history
Formed from silica-rich solutions percolating through sedimentary or volcanic rocks at low temperatures.
Uses & applications
Extensively used as a gemstone in high-end jewelry and highly sought after by mineral collectors.
Geological facts
Precious 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 play-of-color, lower hardness, and amorphous structure; commonly sourced from Australia, Ethiopia, and Mexico.
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