mineral
Opal
Hydrated amorphous silica (SiO2·nH2O)
AI-generated identification · may be incorrectHardness is 5.5 to 6.5 on the Mohs scale. Exhibits a waxy to vitreous luster with a sub-conchoidal to conchoidal fracture.
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Physical properties
Hardness is 5.5 to 6.5 on the Mohs scale. Exhibits a waxy to vitreous luster with a sub-conchoidal to conchoidal fracture.
Formation & geological history
Forms from a solution of silica and water, typically precipitating in cracks and voids of sedimentary or volcanic rocks.
Uses & applications
Primarily used as a gemstone in high-end jewelry and cherished as a prized addition for mineral collectors.
Geological facts
Precious opal displays a unique play-of-color caused by the diffraction of light through microscopic silica spheres.
Field identification & locations
Identified by its characteristic greasy luster and lack of crystal structure; major deposits are found in Australia and Ethiopia.
