mineraloid
Opal
Hydrated amorphous silica (SiO2·nH2O)
AI-generated identification · may be incorrectMohs hardness of 5.5-6.5; displays translucent to opaque bodies with a characteristic play-of-color; vitreous to waxy luster.
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Physical properties
Mohs hardness of 5.5-6.5; displays translucent to opaque bodies with a characteristic play-of-color; vitreous to waxy luster.
Formation & geological history
Formed from silica-rich solutions deposited at low temperatures in fissures or cavities of various rock types.
Uses & applications
Extensively used in high-end jewelry, carvings, and as a prized collector's gemstone.
Geological facts
Precious opals exhibit a unique diffraction of light caused by microscopic silica spheres arranged in a regular grid.
Field identification & locations
Identified by its signature play-of-color and lack of crystalline structure; predominantly mined in Australia.
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