Contribution
Gageite from the Kalahari manganese field, South Africa
Bruiyn, H. de; Westhuizen, W. A. van der; Beukes, G. J.
Neues Jahrbuch für Mineralogie - Monatshefte Jg. 1994 Heft 5 (1994), p. 193 - 204
25 références bibliographiques
publié: May 25, 1994
DOI: 10.1127/njmm/1994/1994/193
ArtNo. ESP156199405001, Prix: 19.00 €
Abstract
A mineralogical description of gageite from the Nchwaning mine in the Kalahari manganese field, South Africa is presented. The mean structural formulae varies between (Mn35.75Fe0.93Mg0.76 Ca0.11Zn0,02[]4.41)42 Si15 (O,OH)90 and (Mn37.33Fe0.87Mg0.87 Ca0,08Zn0.02[]2.81)42 Si15 (O,OH)90 for two different samples respectively. It has a space group of Pnnm and refined unit cell parameters of a° = 13.7928 (± 0.0074) Å, b° = 13.7209 (± 0.0133) Å, c° = 3.2972 (± 0.0022) Å, a: b: c = 1.0052: 1:0.2403 and V = 623.9974 (± 0.6286) Å3 (F31 = 4 [0.0584; 131], M31 = 87). Calculated densities vary between 3.47 and 3.57 g/cm3. Gageite from the Nchwaning mine is of late stage, low temperature hydrothermal origin and occurs as a fibrous mat, encrusting mainly calcite and associated andradite, hausmannite and clinochlore from vugs in the manganese-bearing rocks.
Mots-clefs
Gageite • electron microprobe analyses • X-ray powder diffraction data • Kalahari manganese field