Mimetite is a lead arsenate chloride mineral (Pb5(AsO4)3Cl) which forms as a secondary mineral in lead deposits, usually by the oxidation of galena and arsenopyrite. The name derives from the Greek Μιμητής mimetes, meaning "imitator" and refers to mimetite's resemblance to the mineral pyromorphite. This resemblance is not coincidental, as mimetite forms a mineral series with pyromorphite (Pb5(PO4)3Cl) and with vanadinite (Pb5(VO4)3Cl). Notable occurrences are Mapimi, Durango, Mexico and Tsumeb, Namibia.
Tsumeb is a city of 15,000 inhabitants and the largest town in the Oshikoto region in northern Namibia. Tsumeb is known as the "gateway to the north" of Namibia. It is the closest town to the Etosha National Park. Tsumeb used to be the regional capital of Oshikoto until 2008 when Omuthiya was proclaimed a town and the new capital. The area around Tsumeb forms its own electoral constituency and has a population of 44,113. The town is the site of a deep mine that in its heyday was known as "TCL", but has since been renamed the Ongopolo Mine.
Agardite is a mineral group consisting of agardite-(Y), agardite-(Ce), agardite-(Nd), and agardite-(La). They comprise a group of minerals that are hydrous hydrated arsenates of rare-earth elements (REE) and copper, with the general chemical formula (REE,Ca)Cu6(AsO4)3(OH)6·3H2O. Yttrium, cerium, neodymium, lanthanum, as well as trace to minor amounts of other REEs, are present in their structure. Agardite-(Y) is probably the most often found representative. They form needle-like yellow-green (variably hued) crystals in the hexagonal crystal system. Agardite minerals are a member of the mixite structure group, which has the general chemical formula Cu2+6A(TO4)3(OH)6·3H2O, where A is a REE, Al, Ca, Pb, or Bi, and T is P or As. In addition to the four agardite minerals, the other members of the mixite mineral group are calciopetersite, goudeyite, mixite, petersite-(Ce), petersite-(Y), plumboagardite, and zálesíite.
Geigerite is a mineral, a complex hydrous manganese arsenate with formula: Mn5(AsO3OH)2(AsO4)2·10H2O. It forms triclinic pinacoidal, vitreous, colorless to red to brown crystals. It has a Mohs hardness of 3 and a specific gravity of 3.05.
Legrandite is a rare zinc arsenate mineral, Zn2(AsO4)(OH)·(H2O).
Arthurite is a mineral composed of divalent copper and iron ions in combination with trivalent arsenate, phosphate and sulfate ions with hydrogen and oxygen. Initially discovered by Sir Arthur Russell in 1954 at Hingston Down Consols mine in Calstock, Cornwall, England, arthurite is formed as a resultant mineral in the oxidation region of some copper deposits by the variation of enargite or arsenopyrite. The chemical formula of Arthurite is CuFe23+(AsO4,PO4,SO4)2(O,OH)2·4H2O.
Cabalzarite is a rare arsenate mineral with the chemical formula Ca(Mg,Al,Fe3+
)
2[AsO
4]
2•2(H
2O,OH). It is a member of the tsumcorite group. It crystallizes in the monoclinic system and typically occurs as clusters of crystals or granular aggregates.
Reinerite is a rare arsenite (arsenate(III)) mineral with chemical formula Zn3(AsO3)2. It crystallizes in the orthorhombic crystal system.
Duftite is a relatively common arsenate mineral with the formula CuPb(AsO4)(OH), related to conichalcite. It is green and often forms botryoidal aggregates. It is a member of the adelite-descloizite Group, Conichalcite-Duftite Series. Duftite and conichalcite specimens from Tsumeb are commonly zoned in color and composition. Microprobe analyses and X-ray powder-diffraction studies indicate extensive substitution of Zn for Cu, and Ca for Pb in the duftite structure. This indicates a solid solution among conichalcite, CaCu(AsO4 )(OH), austinite, CaZn(AsO4)(OH) and duftite PbCu(AsO4)(OH), all of them belonging to the adelite group of arsenates. It was named after Mining Councilor G Duft, Director of the Otavi Mine and Railroad Company, Tsumeb, Namibia. The type locality is the Tsumeb Mine, Tsumeb, Otjikoto Region, Namibia.
Plumbogummite is a rare secondary lead phosphate mineral, belonging to the alunite supergroup of minerals, crandallite subgroup. Some other members of this subgroup are:
Lavendulan is an uncommon copper arsenate mineral, known for its characteristic intense electric blue colour. It belongs to the lavendulan group, which has four members:
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.
Sewardite is a rare arsenate mineral with formula of CaFe3+2(AsO4)2(OH)2. Sewardite was discovered in 1982 and named for the mineralogist, Terry M. Seward (born 1940), a professor of geochemistry in Zürich, Switzerland.
Keyite is a mineral with the chemical formula Cu2+3Zn4Cd2(AsO4)6 · 2H2O. The name comes from Charles Locke Key, an American mineral dealer who furnished its first specimens. Keyite is monoclinic-prismatic, meaning its crystal form has three unequal axes, two of which have 90° angles between them and one with an angle less than 90°. Keyite belongs to the biaxial optical class, meaning it has more than one axis of anisotropy, in which light travels with zero birefringence, and three indices of refraction, nα = 1.800, nβ, and nγ = 1.870. Being a very rare cadmium copper arsenate, keyite is only found in Tsumeb, Namibia in the Tsumeb mine, a world-famous copper mine known for its abundance of rare and unusual minerals.
Tsumcorite is a rare hydrated lead arsenate mineral that was discovered in 1971, and reported by Geier, Kautz and Muller. It was named after the TSUMeb CORporation mine at Tsumeb, in Namibia, in recognition of the Corporation's support for mineralogical investigations of the orebody at its Mineral Research Laboratory.
Ianbruceite is a rare hydrated zinc arsenate with the formula [Zn2(OH)(H2O)(AsO4)](H2O)2; material from the Driggith mine has traces of cobalt. It was first discovered at Tsumeb, approved by the International Mineralogical Association as a new mineral species in 2011, reference IMA2011-49, and named for Ian Bruce, who founded "Crystal Classics" in the early 1990s, and was heavily involved in attempts to reopen the famous Tsumeb mine for specimen mining.
In 2013 new occurrences of ianbruceite were reported from the neighbouring Driggith and Potts Gill mines on High Pike in the Caldbeck Fells, Cumbria, England. Here the mineral is probably a post-mining product. Caldbeck Fells and Tsumeb are the only reported localities for ianbruceite to date (May 2013).
Köttigite is a rare hydrated zinc arsenate which was discovered in 1849 and named by James Dwight Dana in 1850 in honour of Otto Friedrich Köttig (1824–1892), a German chemist from Schneeberg, Saxony, who made the first chemical analysis of the mineral. It has the formula Zn3(AsO4)2·8H2O and it is a dimorph of metaköttigite, which means that the two minerals have the same formula, but a different structure: köttigite is monoclinic and metaköttigite is triclinic. There are several minerals with similar formulae but with other cations in place of the zinc. Iron forms parasymplesite Fe2+3(AsO4)2·8H2O; cobalt forms the distinctively coloured pinkish purple mineral erythrite Co3(AsO4)2·8H2O and nickel forms annabergite Ni3(AsO4)2·8H2O. Köttigite forms series with all three of these minerals and they are all members of the vivianite group.
Talmessite is a hydrated calcium magnesium arsenate, often with significant amounts of cobalt or nickel. It was named in 1960 for the type locality, the Talmessi mine, Anarak district, Iran. It forms a series with β-Roselite, where cobalt replaces some of the magnesium, and with gaitite, where zinc replaces the magnesium. All these minerals are members of the fairfieldite group. Talmessite is dimorphic with wendwilsonite.
Bartelkeite is an exceptionally rare mineral, one of scarce natural germanium compounds. The formula was originally assumed to be PbFeGe3O8, bartelkeite was later shown to be isostructural with a high-pressure form of the mineral lawsonite. Thus, its correct formula is PbFeGe(Ge2O7)(OH)2•H2O. Bartelkeite and mathewrogersite are minerals with essential (dominant) lead, iron and germanium. Both come from Tsumeb, Namibia - a world's "capital" of germanium minerals.
Arsendescloizite is a lead-zinc mineral, approved by the IMA in 1982. It is an arsenate analog of descloizite. Its first description was published in 1982.
