Zoisite (7.18g)

specimen number:
1052753

location:
Merelani Hills, Manyara, Tanzania

description:

A loose gem crystal of zoisite, this is the variety known as tanzanite. In great condition all around. The crystal exhibits the color change as shown at the end of the video.

The Merelani Hills, situated in the Lelatema Mountains of the Manyara Region in northern Tanzania, host a globally unique mining district famous for producing tanzanite, a rare vanadium-rich variety of zoisite. Geologically, the deposit consists of a complex Neoproterozoic-age metamorphic sequence belonging to the Mozambique Orogenic Belt, where intense regional crustal folding and high-pressure metamorphism altered local sedimentary rocks into graphitic gneiss, kyanite schist, and boudinaged marble layers. Hydrothermal solutions migrating through these highly deformed structures interacted with the vanadium-bearing graphitic schists, precipitating idiomorphic, trichroic crystals of zoisite, along with exceptional tsavorite garnet, diopside, and prehnite within structural boudin pockets and quartz-calcite veins. Historically, the formal discovery of tanzanite in 1967 by a local Maasai tribesman sparked an immediate surface rush, leading to widespread open-cut quarrying and small-scale artisanal pits across the rugged hillsides. The Tanzanian government nationalized the mining zones in 1971, later subdividing the district into distinct operating blocks (Blocks A, B, C, and D) in the 1990s to separate regulated, deep-level corporate underground shaft operations from independent small-scale artisanal mining, both of which remain highly active in extracting these specialized gemstone deposits through 2026.

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