gemstone
Opal
SiO2·nH2O (Hydrated Silica)
AI-generated identification · may be incorrectMohs hardness of 5.5 to 6.5, variable body colors with a distinctive play-of-color, subvitreous to greasy luster, and amorphous crystal structure.
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Physical properties
Mohs hardness of 5.5 to 6.5, variable body colors with a distinctive play-of-color, subvitreous to greasy luster, and amorphous crystal structure.
Formation & geological history
Formed from a solution of silica and water, typically deposited in fissures or cavities in sedimentary and volcanic rocks over millions of years.
Uses & applications
Primarily used as a high-value gemstone in fine jewelry, rings, necklaces, and collector displays.
Geological facts
Opal contains up to 20% water trapped within its microscopic silica spheres, which diffract light to create its rainbow effect.
Field identification & locations
Identified easily by its signature play-of-color flash and amorphous fracture; major deposits are found in Australia, Ethiopia, and Mexico.
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