Tsumebite

A variety of Minerals

Tsumebite specimen - rock identification

What is Tsumebite?

Tsumebite is a rare phosphate mineral named in 1912 after the locality where it was first found, the Tsumeb mine in Namibia, well known to mineral collectors for the wide range of minerals found there. Tsumebite is a compound phosphate and sulfate of lead and copper, with hydroxyl, formula Pb2Cu(PO4)(SO4)(OH). There is a similar mineral called arsentsumebite, where the phosphate group PO4 is replaced by the arsenate group AsO4, giving the formula Pb2Cu(AsO4)(SO4)(OH). Both minerals are members of the brackebuschite group.

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Tsumebite Localities Map

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North ZoneCentral RidgeSouth Basin

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Key Characteristics

Characteristics of Tsumebite

The mineral typically occurs as crusts of intergrown crystals on matrix. Cleavage is absent, but twinning is almost universal, and twins may be multiple, with serrated re-entrants. It is brittle, with an uneven fracture, hardness ​3 ⁄2 and specific gravity 6.13. It is readily soluble in hydrochloric acid HCl and slowly soluble in nitric acid HNO3. It is not radioactive.

Composition of Tsumebite

The structure of the brackebuschite group minerals is composed of B-(O,OH)6 octahedra, two non-equivalent TO4 tetrahedra, TO4(1) and TO4(2), and two different irregular polyhedra of large cations. B and T represent different elements in different members of the group. Chains formed from the B octahedra link through the oxygens of TO4(2) tetrahedra, while the large cation polyhedra form double chains parallel to the b crystal axis through edge sharing with TO4(1) tetrahedra. The result is a tight three-dimensional structure. In tsumebite copper ions occupy the B sites, and phosphorus and sulfur occupy the T sites. Lead is the large cation.

Quick Facts

Physical Properties

Color
Emerald-green sometimes bluish green; green in transmitted light.
Hardness (Mohs)
3.5
Density
6.22 g/cm³
Streak
White to faint green

Chemical Properties

Chemical Formula
Pb2Cu(PO4)(SO4)(OH)
Elements
Cu, H, O, P, Pb, S
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