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