Tremolite

specimen number:
2072068

location:
Merelani Hills, Arusha, Tanzania

description:
A loose mostly gemmy green crystal of tremolite. In good condition.

The Merelani Hills are located in the Lelatema Mountains of the Simanjiro District, Tanzania, and are world-renowned as the only source of tanzanite. Geologically, the deposit is hosted within the Mozambique Metamorphic Belt, specifically in Neoproterozoic-aged high-grade metamorphic rocks such as kyanite-graphite schists and gneisses. The mineralization occurred during the Pan-African orogeny, approximately 585 million years ago, as intense heat and pressure transformed chemical elements within the earth. While the site is most famous for zoisite, it also produces exceptional specimens of chrome tremolite. This vibrant green silicate mineral owes its color to trace amounts of chromium and typically forms in the same hydrothermal veins as tanzanite and tsavorite garnet. The timeline of collecting in the Merelani Hills began in 1967 with the discovery of blue zoisite, but interest in the secondary minerals like chrome tremolite grew significantly in the 1980s and 1990s as artisanal miners expanded their operations. These specimens are highly sought after for their sharp, transparent, emerald-green prismatic crystals, which often exhibit a distinct pleochroism. Today, Merelani remains an active and strictly regulated mining area, continuing to provide some of the finest examples of chrome-bearing amphiboles found anywhere in the world.

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