mineral
Bicolor Tanzanite
Zoisite (Ca2Al3(SiO4)3(OH))
Hardness: 6-7 Mohs; Color: Distinct blue and violet/pink zones; Luster: Vitreous; Crystal system: Orthorhombic; Cleavage: One perfect; Specific Gravity: 3.35.
- Hardness
- 6-7 Mohs
- Color
- Distinct blue and violet/pink zones
- Luster
- Vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Distinct blue and violet/pink zones; Luster: Vitreous; Crystal system: Orthorhombic; Cleavage: One perfect; Specific Gravity: 3.35.
Formation & geological history
Formed in regional metamorphic environments where calcium-rich rocks were subjected to high heat and pressure, specifically within marble/quartzite layers during the Pan-African orogenic event (approx. 585 million years ago).
Uses & applications
Primarily used as a gemstone in high-end jewelry (rings, pendants, earrings) and as a highly sought-after specimen for investment collectors.
Geological facts
Tanzanite is 1,000 times rarer than diamonds because it is only found in a small 4km x 2km area near Mount Kilimanjaro. It is famous for its strong trichroism, showing blue, violet, and burgundy colors when viewed from different angles.
Field identification & locations
Identify by its pleochroism (color shifting) and specific gravity. It is only found in the Merelani Hills of Tanzania. Collectors look for 'fancy' colors or sharp bicolor zoning.
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metamorphic
Gypsum (variety Selenite or Alabaster)
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Mineral
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