Dravite

specimen number:
2133258

location:
Landanai, Manyara, Tanzania

description:

A blocky lustrous green slightly translucent double terminated crystal of dravite on a small amount of matrix. In great condition. This is a superb thumbnail.

The Landanai area, situated in the Simanjiro District of the Manyara Region in Tanzania, is a significant locality within the Neoproterozoic Mozambique Belt. Geologically, the region features high-grade metamorphic rocks, specifically graphite-bearing schists and marbles, where pegmatitic and hydrothermal activities have facilitated the growth of various gemstone-quality minerals. Mining at Landanai is primarily a small-scale, artisanal effort that gained momentum in the late 20th century as part of the broader East African gemstone boom, with various pits and shafts operating sporadically from the 1980s through to the present day. While the area is known for producing various types of tourmaline and garnet, it is most famous in the mineralogical community for its distinct crystals found in the contact zones of metamorphic host rocks.

The dravite tourmaline from Landanai is highly prized for its exceptional forest-green to emerald-green color, which is remarkably vibrant compared to the typically brown or black hues of standard dravite. This intense green coloration is caused by the presence of trace amounts of vanadium (V3+) substituting for aluminum in the crystal lattice, often with minor contributions from chromium. This specific chemistry classifies the material as vanadium dravite, a rare variety where the lack of significant iron allows the bright green transmission of light to remain pure and saturated. These specimens are often found as well-formed, lustrous crystals that are highly sought after by both gem cutters and mineral collectors for their unique geological signature.

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