Calcium aluminum silicate. The blue-violet variety tanzanite is one of the most valued gemstones, found only in Tanzania. Color: Gray, green, blue-violet tanzanite , pink thulite. Luster: Vitreous to pearly. Streak: White. Cleavage: Perfect in one direction. Hardness: 6-6.5. Transparency: Transparent to translucent. Crystal system: Orthorhombic. Chemical formula: Ca₂Al₃ SiO₄ ₃ OH. Specific gravity: 3.15-3.36. Formation: Forms during medium-grade metamorphism of calcium-rich rocks; tanzanite from contact metamorphism near gneiss. Common geological settings: Tanzania tanzanite , Austria, Norway thulite , Kenya; found in metamorphic rocks. Common look-alikes and related entries: Epidote, Clinozoisite, Sapphire.
These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.
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GeoMiner
Last updated
2026-03-30T14:36:55.272548+00:00
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Published; not independently peer-reviewed
IMA–CNMNC List of Mineral Names — International Mineralogical Association. Official mineral-name, nomenclature, and classification records.
Mineral ID Key — Mineralogical Society of America. Physical-property identification methods, repeat-testing guidance, and limitations.
Calcium aluminum silicate. The blue-violet variety tanzanite is one of the most valued gemstones, found only in Tanzania.
How can you identify Zoisite?
Compare several properties rather than relying on colour alone. This entry records colour: Gray, green, blue-violet tanzanite , pink thulite; lustre: Vitreous to pearly; streak: White; Mohs hardness: 6-6.5; cleavage: Perfect in one direction; crystal system: Orthorhombic; transparency: Transparent to translucent. Confirm an important identification with additional field tests or qualified laboratory work.
How does Zoisite form?
Forms during medium-grade metamorphism of calcium-rich rocks; tanzanite from contact metamorphism near gneiss.
Where is Zoisite commonly found?
Tanzania tanzanite , Austria, Norway thulite , Kenya; found in metamorphic rocks.
What is Zoisite commonly confused with?
Zoisite may be confused with Epidote, Clinozoisite, Sapphire. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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