Prehnite

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Mineral guide

Learn about Prehnite

apple- to mint-green crystals and sculptural botryoidal/rosette forms; a calcium aluminum silicate formed in low-temp hydrothermal environments.

Regional guide

Prehnite from Merelani Hills, Tanzania

Merelani Hills prehnite is one of the surprises of a locality that collectors first learned to revere for tanzanite. In hand specimen it is immediately recognizable: glassy yellow-green to lemon-yellow clusters, bright mint-green blades, and occasional blue to celestine-blue rosettes, commonly sharpened by the dark metallic contrast of graphite. The best examples have the translucency and internal glow of gem material, but with the crystallographic interest of discrete tabular, blocky, bladed, or rosette crystals rather than the more familiar botryoidal prehnite seen from many classic basalt localities.