Corundum

specimen number:
9711718

location:
Gairo, Morogoro, Tanzania

description:
Several pinkish red prismatic crystals of corundum, this the variety known as Ruby, measuring to 4.3 cm in length embedded up on matrix. Brightly fluorescent, in good condition.

Gairo, located in the Morogoro Region of Tanzania, forms part of a broader East African mineral district that gained sporadic attention for artisanal ruby and pink sapphire discoveries beginning around the 1970s, with small-scale and informal workings operating intermittently rather than following a strict corporate opening and closing timeline. Geologically, the area sits within the ancient, high-grade metamorphic rocks of the Mozambique orogenic belt (specifically the Eastern Granulites and Neoproterozoic basement formations), where intense tectonic folding, regional metamorphism, and fluid circulation through marble and calc-silicate units created ideal conditions for the crystallization of gem-quality corundum. The local ruby deposits typically occur in small, structurally controlled lenses or secondary eluvial gravels, producing distinct reddish-pink hexagonal crystals and matrix specimens characterized by strong chromium-driven fluorescence.

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