mineral
Rough Topaz
Aluminum silicate fluoride hydroxide (Al2SiO4(F,OH)2)
Hardness: 8.0 on Mohs scale. Color: Pale yellow to colorless. Luster: Vitreous to sub-vitreous. Crystal Structure: Orthorhombic. Cleavage: Perfect basal (one direction). Specific Gravity: 3.4 to 3.6.
- Hardness
- 8
- Color
- Pale yellow to colorless
- Luster
- Vitreous to sub-vitreous
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Physical properties
Hardness: 8.0 on Mohs scale. Color: Pale yellow to colorless. Luster: Vitreous to sub-vitreous. Crystal Structure: Orthorhombic. Cleavage: Perfect basal (one direction). Specific Gravity: 3.4 to 3.6.
Formation & geological history
Formed by fluorine-bearing vapors given off during the last stages of the crystallization of igneous rocks. It is most commonly found in pegmatite dikes, rhyolite lava flows, and alluvial deposits.
Uses & applications
Frequently used as a gemstone in jewelry when faceted; industrial uses include use as an abrasive in some glass-making processes due to high hardness.
Geological facts
Topaz is one of the hardest minerals found in nature. A common misconception is that all yellow gemstones are topaz, but true topaz is chemically distinct and much heavier/harder than citrine quartz.
Field identification & locations
Identified in the field by its high hardness (scratches quartz), high density (it feels heavy for its size), and its characteristic crystal shape or basal cleavage. Commonly found in Brazil, Pakistan, and Russia.
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Metamorphic
Epidote
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Mineral
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