gemstone
Blue Topaz
Al2SiO4(F,OH)2
Hardness of 8 on the Mohs scale, color ranges from pale sky blue to deep Swiss and London blue, vitreous luster, orthorhombic crystal system, perfect basal cleavage, specific gravity of 3.49-3.57.
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Physical properties
Hardness of 8 on the Mohs scale, color ranges from pale sky blue to deep Swiss and London blue, vitreous luster, orthorhombic crystal system, perfect basal cleavage, specific gravity of 3.49-3.57.
Formation & geological history
Formed in pegmatites, high-temperature quartz veins, and cavities in granitic and rhyolitic igneous rocks through the action of fluorine-bearing vapors during the final stages of rock crystallization.
Uses & applications
Widely used in fine jewelry such as rings, necklaces, and earrings; also used in industrial applications requiring abrasive materials, though natural blue topaz is rare and most commercial stones are enhanced colorless topaz.
Geological facts
Natural blue topaz is exceptionally rare; most blue topaz on the market is produced by treating colorless topaz with irradiation and heat. Topaz is the birthstone for December.
Field identification & locations
Can be identified in jewelry by its hardness, distinct cold touch, high refractive index, and specific gravity. Mined in Brazil, Sri Lanka, Nigeria, and the United States.
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