Colimaite, K3VS4 – a new potassium-vanadium sulfide mineral from the Colima volcano, State of Colima (Mexico)

Abstract

Colimaite, K3VS4, has been discovered in the active fumaroles of the Colima volcano crater, Mexico. The mineral is named colimaite after the locality, which, at the same time, is the current active volcanic crater and the name of the State of Colima (Mexico). Colimaite is the naturally occurring analog of synthetic K3VS4. The mineral formed as a sublimate from the volcanic gases and is associated with cristobalite, arcanite, thenardite, barite and native gold. Colimaite occurs in “hedgehog”-like particles, which contain the needle crystals, up to 50 µm length and 20 µm width. Electron microprobe analyses gave S=43.29 %, K=39.36 %, V=17.41 %, Na=0.43 %, with the sum of 100.49 (wt.%), as the mean of six measurements, previously tested as discordant outlier-free statistical samples. The empirical formula, calculated on the basis of eight atoms, is (K2.95Na0.06)Σ3.01V1.03 S3.97. The idealized formula is K3VS4. The Selected Area Electron Diffraction (SAED) and X-ray powder diffraction data (Cu Kα radiation) indicated that the structure of the micro-sized particles correspond to the orthorhombic K3VS4 crystalline phase: space group Pnma, with a=9.139 (5), b=10.625 (7), c=9.135 (3) Å, V=887.03 (9) Å3, and Z=4. The five strongest calculated diffraction lines from this natural compound are [d in Å, (I) (hkl)]: 2.806 (100)(230), 3.463 (73)(220), 2.785 (70)( 113), 2.928 (67)(013), and 2.677 (63)(132). SAED patterns are quite similar to those of the synthetic K3VS4. The calculated density (Z=4) is 2.235 g cm-3. The main observed Raman bands lie in the region below 500 cm-1 and the most characteristic bands occur between 150 and 300 cm-1: 192, 203, 245, 264, 277 and 297 cm-1. Colimaite, K3VS4, is the first newly recognized mineral species collected from an active fumarole in this volcanic crater. The mineral and the mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA # 2007-045).