Zoisite (Ca₂Al₃(SiO₄)(Si₂O₇)O(OH)) is the orthorhombic sister to monoclinic epidote and a calcium-aluminum sorosilicate of major collector and gem importance. The species hosts three iconic gem varieties: tanzanite (vivid blue-violet, V/Cr-bearing) from the Merelani Hills in Tanzania, thulite (vivid pink, Mn-bearing) from Norway, and anyolite (“ruby in zoisite,” massive green Zoisite enclosing ruby crystals). Tanzanite is the second-most popular blue gem after sapphire and is mined exclusively from a small region of Tanzania.
Key Facts
- Mohs hardness 6–7.
- Orthorhombic; prismatic and columnar habits with deep striations.
- Strong pleochroism in tanzanite (blue / violet / brownish-yellow on three optical axes).
- Tanzanite is heat-treated commercially to enhance the blue color from the as-mined brownish hue.
- Member of the epidote group sensu lato — closely related structurally to monoclinic epidote.
Notable Localities
Merelani Hills (Tanzania) is the sole world source of gem tanzanite. Sauland (Norway) is the type locality for thulite. Longido (Tanzania) supplies anyolite (ruby-in-zoisite).
Found at these Localities
- Merelani Hills (梅雷拉尼山(坦桑石产地))
