Köttigite

kottigite

parasymplesite

skutterudite

legrandite

Images

Formula: Zn₃(AsO₄)₂.8H₂O
Hydrated normal arsenate, vivianite group, forms a series with parasymplesite (Mindat), erythrite and annabergite (Dana, HOM).
Specific gravity: 3.33
Hardness: 2½ to 3
Streak: Reddish-white to white
Colour: Colorless, carmine-red, red-orange, brown; light rose-pink in transmitted light
Solubility: Soluble in acids (Mindat, Dana)
Environments

Hydrothermal environments

Köttigite is a rare secondary mineral in the oxidation zone of some zinc deposits (HOM) formed from the alteration of skutterudite and sphalerite (Webmin, Dana). Skutterudite and sphalerite are common associates (Mindat).

Localities

At the Clara mine, Baden-Württemberg, Germany, until the 1980s köttigite had been considered extremely rare, having been found only as fibrous crystal clusters a few millimeters in size, perched on quartz. In the mid-1980s köttigite crystals up to 3 cm in size were found here, on a quartz / baryte matrix (R&M 90.1.45).

At the type locality, the Daniel Mine, Saxony, Germany, köttigite occurs in oxidised veins in a hydrothermal sulphide ore deposit, associated with roselite (Mindat).

At the Ojuela mine, Mexico, köttigite is associated with symplesite, parasymplesite, adamite, legrandite, metaköttigite and gypsum (HOM).

At Taghouni, Bou Azzer, Morocco, köttigite has been found in a sample of vein quartz richly infused with chalcopyrite and sphalerite, associated with devilline (Minrec 38.5.381).

At Tsumeb, Namibia, köttigite is associated with cuprian adamite (HOM).

At Sterling Hill, New Jersey, USA, köttigite is associated with pharmacosiderite, legrandite, scorodite and adamite (HOM).

Alteration

The Activity-pH diagram below was calculated at 298.2 K for some zinc arsenates and Ca₃(AsO₄)₂ for constant activity (roughly equivalent to concentration) of Ca²⁺ ions in solution, over a range of values of pH and of Zn²⁺ activity (MM 52.685).


The zinc mineral formulae are:
adamite: Zn₂(AsO₄)(OH)
köttigite: Zn₃(AsO₄)₂.8H₂O
austinite: CaZn(AsO₄)(OH)













Back to Minerals