What is "tsumebite"

n. a mixed basic phosphate and sulphate of lead and copper that is found as green crystals

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 PbCu(PO)(SO)(OH). There is a similar mineral called arsentsumebite, where the phosphate group PO is replaced by the arsenate group AsO, giving the formula PbCu(AsO)(SO)(OH). Both minerals are members of the brackebuschite group.