TY - JOUR A1 - Cempirek,J. A1 - Groat,L.A. T1 - Note on the formula of brunogeierite and the first bond-valence parameters for Ge2+ JF - Journal of Geosciences JA - J. Geosci. Y1 - 2013 VL - 58 IS - 1 SP - 71 EP - 74 CY - Prague PB - Czech Geological Society SN - 1803-1943 (online), 1802-6222 (print) AV - Free UR - http://dx.doi.org/10.3190/jgeosci.130 L1 - http://www.jgeosci.org/content/jgeosci.130_cempirek.pdf KW - germanium KW - spinel-type structure KW - ringwoodite group KW - bond-valence model AB - Brunogeierite is a rare Ge-mineral with a spinel-type structure. Inconsistences in the brunogeierite formula suggesting divalent germanium in its structure have occurred since its description. A review of the published data and bond-valence calculations show that the correct ideal end-member formula of brunogeierite is (Fe2+)2Ge4+O4. The mineral is newly classified as a nesogermanate member of the ringwoodite group (Strunz classification 9.AC.15). Formal correction of the brunogeierite formula and classification was approved by the IMA Commission on New Minerals, Nomenclature and Classification (IMA-CNMNC) as proposal IMA 11-A. To perform bond-valence calculations using divalent germanium, new bond-valence parameters for Ge2+-O (R0 = 1.778 Å, B = 0.37 Å) and Ge2+-Cl (R0 = 2.156 Å, B = 0.37 Å) were evaluated. ER -