TY - JOUR

T1 - Ion substitutions and structural adjustment in Cr-bearing tourmalines

AU - Vereshchagin, O.S.

AU - Rozhdestvenskaya, I.V.

AU - Frank-Kamenetskaya, O.V.

AU - Zolotarev, A.A.

PY - 2014

Y1 - 2014

N2 - The geological settings of Cr-bearing tourmaline occurrences are reviewed and the crystal chemistry of Cr-bearing tourmalines is analysed on the basis of new X-ray single-crystal structure refinements (R0.019–0.025) of three crystals from the Ural deposits (Cr2O3 content ∼6 wt.%) and one from Umba Valley, Tanzania (∼1 wt.% Cr2O3) and published data (13 structures) on tourmalines from different deposits with Cr content up to 36 oxide wt.%. The boundary between the ordered and the disordered distribution of Cr between Y and Z octahedral sites is determined near 1.03 ± 0.27 Cr apfu and relationships between Cr content and structural parameters (unit-cell parameters, octahedral bond-lengths, charge of Y and Z sites and polyhedral deformation) are established. An increasing Cr content in tourmaline causes an increase of both lattice parameters, of and bond-lengths and a regular variation of the charge of the Y and Z octahedra. In general, the structure becomes less deformed by reducing the distortion of the octahe

AB - The geological settings of Cr-bearing tourmaline occurrences are reviewed and the crystal chemistry of Cr-bearing tourmalines is analysed on the basis of new X-ray single-crystal structure refinements (R0.019–0.025) of three crystals from the Ural deposits (Cr2O3 content ∼6 wt.%) and one from Umba Valley, Tanzania (∼1 wt.% Cr2O3) and published data (13 structures) on tourmalines from different deposits with Cr content up to 36 oxide wt.%. The boundary between the ordered and the disordered distribution of Cr between Y and Z octahedral sites is determined near 1.03 ± 0.27 Cr apfu and relationships between Cr content and structural parameters (unit-cell parameters, octahedral bond-lengths, charge of Y and Z sites and polyhedral deformation) are established. An increasing Cr content in tourmaline causes an increase of both lattice parameters, of and bond-lengths and a regular variation of the charge of the Y and Z octahedra. In general, the structure becomes less deformed by reducing the distortion of the octahe

U2 - 10.1127/0935-1221/2014/0026-2372

DO - 10.1127/0935-1221/2014/0026-2372

M3 - Article

VL - 26

SP - 309

EP - 321

JO - European Journal of Mineralogy

JF - European Journal of Mineralogy

SN - 0935-1221

IS - 2

ER -