gemstone
Blue Topaz
Al2SiO4(F,OH)2 (Aluminum silicate fluoride hydroxide)
Hardness: 8, Color: Swiss Blue, Luster: Vitreous (glassy), Crystal Structure: Orthorhombic, Cleavage: Perfect basal (001), Specific Gravity: 3.49-3.57
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Physical properties
Hardness: 8, Color: Swiss Blue, Luster: Vitreous (glassy), Crystal Structure: Orthorhombic, Cleavage: Perfect basal (001), Specific Gravity: 3.49-3.57
Formation & geological history
Found in pegmatites and high-temperature quartz veins. Most commercial blue topaz is natural colorless topaz that has been irradiated and heat-treated to produce blue hues.
Uses & applications
Primarily used as a gemstone in rings, necklaces, and facets. Also used as hard-bearing material in delicate instruments.
Geological facts
Topaz is the state gemstone of Utah and the birthstone for December (Blue) and November (Yellow). While naturally occurring blue topaz exists, it is extremely rare without human treatment.
Field identification & locations
Identify by its high hardness (scratches glass/quartz) and heavy weight for its size. The location (Jalisco, Mexico) is famous for volcanic regions where minerals like obsidian and fire opal are common, but cut gems like this are usually commercial imports.
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