Home > Mexico II Type Locales – December 22 > MS1706 Metaköttigite

Metaköttigite


Metaköttigite is a zinc iron arsenate hydrate. Schmetzer et al. (1982) named this mineral for its relationship to köttigite, a species found more than century earlier in Germany. Metaköttigite is triclinic whereas köttigite is monoclinic; both with similar crystal structures. Trivalent iron in metaköttigite leads to dissociation of molecular water in the crystal structure for charge balance, disrupting the mirror symmetry of the köttigite structure. Since the iron(III) content in metaköttigite is necessary to disrupt the mirror plane symmetry, and monoclinic köttigite forms with or without iron, these two minerals are not quite polymorphs, despite their marked chemical similarities.

Metaköttigite here forms prismatic crystals to 2 mm forming a rich coverage this "limonite" matrix. A pulverent white material is also present, which is most likely amorphous. This specimen was part of the Charles Trantham (1936-2020) estate; a label from his mineral business CT Minerals accompanies the specimen.

Price: $400

Item code: MS1706

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