Mineral Species
Ianbruceite
Type Locality
Yes
Composition
Zn2(AsO4)(OH)(H2O)·2H2O
Crystal System
Monoclinic
Status at Tsumeb
Confirmed (type locality)
Abundance
Extremely rare
Distribution
Third oxidation zone
Paragenesis
Supergene
Entry Number
Species; TSNB176
Type Mineralogy
The discovery of ianbruceite is credited to German collector Dr Georg Gebhard who, in 1994, acquired specimens from the so-called "Zinc Pocket" on 44 Level in the third oxidation zone. A specimen of leiteite was overgrown by dark blue crystals of köttigite and pale blue crystals of an unknown mineral, to which Gebhard (1999) assigned the designation "GS17". The unknown mineral was investigated independently by workers from the University of Manitoba and the Royal Ontario Museum, and the University of Hamburg. Their data and conclusions were combined for submission to the IMA and for subsequent publication. Ianbruceite, IMA 2011-049 is a hydroxy-hydrated zinc arsenate, named for Ian Bruce owner of the Crystal Classics mineral dealership in the United Kingdom (Cooper et al. 2012; Southwood 2016). The holotype specimen is conserved at the Royal Ontario Museum (catalogue number M53150) and holotype crystals are held at the Mineralogisches Museum, Universität Hamburg, (catalogue number TS 119B).
General Notes
The type specimen is from the so-called "Zinc Pocket" on 44 level, in the third oxidation zone. It was acquired by Georg Gebhard in 1994, and is figured in Gebhard (1999, p.296); this (then-uncharacterised) mineral was designated GS17 by Gebhard.
Ianbruceite occurs as aggregates of thin plates and tapered platy crystals (to 80 µm in length and a few µm thick) and in rounded ellipsoidal aggregates to 0.5 mm across. On the type specimen it is associated with coarse white leiteite, dark blue (Cu-bearing) köttigite, minor legrandite and adamite (Cooper et al. 2012).
A co-type specimen for ianbruceite is in the Pinch Collection at Harvard University (MGMH 2020.7.674). Studies of this specimen (initiated by Pinch, with analyses by Andy Roberts and Frank Hawthorne) indicate that the dark blue "köttigite" associated with ianbruceite may, in fact, be blue legrandite (Bill Pinch, pers. comm. to M. Southwood, 2015). Further work is required; however, ianbruceite, köttigite, and legrandite all share very similar chemistry as hydrated zinc arsenates.
Associated Minerals
adamite; johillerite; köttigite; legrandite; leiteite; reinerite; stranskiite; warikahnite
