Köttigite

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.

The group members are annabergite, arupite, babanekite, baricite, erythrite, hornesite, kottingite, manganhornesite, pakhomovskyite, parasymplesite and vivianite.

[2][3] Although zinc is the only transition metal that appears in the formula, köttigite usually contains significant quantities of cobalt and nickel,[3] and these three elements are randomly distributed over the cation sites to form complex slabs perpendicular to the b axis.

[3] Pure end-member köttigite is colourless, but frequently samples are coloured pink, red, red-orange or brown by elements substituting for the zinc.

[6] At the Ojuela Mine, Mapimí Municipality, Mexico, it occurs in sprays of bladed crystals to 6 mm, which is large for the species,[4] associated with symplesite Fe2+3(AsO4)2·8H2O, parasymplesite Fe2+3(AsO4)2·8H2O, adamite Zn2(AsO4)(OH), legrandite Zn2(AsO4)(OH)·H2O, metaköttigite Zn3(AsO4)2·8H2O and gypsum Ca(SO4)·2H2O.

[5] At the Hilton Mine, Cumbria, England, köttigite has been found in a specimen of galena PbS and gersdorffite NiAsS (but no sphalerite), on a surface coated with annabergite Ni3(AsO4)2·8H2O and an earthy crust.

[8] At Bou Azzer, Taznakht, Morocco, köttigite has been identified in a sample of vein quartz SiO2 rich in chalcopyrite CuFeS2 and sphalerite ZnS.

The sample has turquoise-blue secondary minerals including devilline CaCu4(SO4)2(OH)6·3H2O, and also lath-shaped, blue-grey to pinkish grey crystals of köttigite with a habit resembling erythrite Co3(AsO4)2·8H2O, measuring less than 2 mm.