Formula: (Zn,Fe3+)3(AsO4)2.8(H2O,OH)
Hydrated normal arsenate, symplesite group
Hardness: 1½ to 2½
Colour: Grey

Hydrothermal environments

Metaköttigite ia a rare secondary arsenate from the oxide zone of an arsenic-rich polymetallic mineral deposit, formed by oxidation and concomitant dehydrogenisation of ferroan köttigite. Associated minerals include köttigite, smithsonite, adamite and goethite (HOM).

At the type locality, the Ojuela Mine, Mapimí, Mapimí Municipality, Durango, Mexico, metaköttigite is found on massive samples of fine-grained goethite and smithsonite, together with köttigite and adamite. Metakottigite occurs in minute crystals in oriented intergrowth with köttigite. It is considered that oxidation of Fe2+ to Fe3+ and the simultaneous conversion of H2O to OH- determines the transition from monoclinic köttigite to triclinic metaköttigite, as in the change from vivianite to metavivianite (AM 68.1039, Dana).

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