gemstone
Fire Opal
Hydrated amorphous silica (SiO2·nH2O)
AI-generated identification · may be incorrectMohs hardness of 5.5 to 6.5, vibrant orange-red to yellow color, vitreous to greasy luster, amorphous crystal structure with no cleavage.
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Physical properties
Mohs hardness of 5.5 to 6.5, vibrant orange-red to yellow color, vitreous to greasy luster, amorphous crystal structure with no cleavage.
Formation & geological history
Forms in low-temperature hydrothermal veins and volcanic cavities when silica-rich water deposits in crevices, typically in Tertiary volcanic environments.
Uses & applications
Extensively used in high-end jewelry, cabochons, and as a prized collector gemstone.
Geological facts
Unlike common opals, fire opals are valued for their bright body color rather than play-of-color, though exceptional specimens can display both.
Field identification & locations
Identified by its distinctive warm coloration, conchoidal fracture, and lack of crystal cleavage; primarily mined in Mexico and Ethiopia.
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