Iwashiroite-(Y), YTaO4, a new mineral from Suishoyama, Kawamata Town, Fukushima Prefecture, Japan

Hidemichi HORI, Toshinori Kobayashi, Ritsuro MIYAWAKI, Satoshi MATSUBARA, Kazumi YOKOYAMA, Masaaki SHIMIZU
2006 Journal of Mineralogical and Petrological Sciences  
Iwashiroite (Y), YTaO 4 , was found from Suishoyama, Kawamata Town, Fukushima Prefecture, Japan. It is monoclinic, P2/a, a = 5.262 (5) Å, b = 5.451(5) Å, c = 5.110(5) Å, β = 95.12(10)°, V = 146.0(2) Å 3 , Z = 2. The five strongest lines in the powder XRD pattern [d(Å), I/I 0 , hkl] are (Lu 2 O 3 0.85, ThO 2 0.02, UO 2 0.15, CaO 0.17, Ta 2 O 5 40.64, Nb 2 O 5 16.66, TiO 2 0.41, total 98.60 wt%, and leads to the empirical formula, (Y 0.on the basis of the 4 oxygen atoms per formula unit.
more » ... te (Y) is translucent and amber brown to brown in color with a glassy to subadamantine luster. The streak is pale brown and cleavage is {010} good, {001} poor. The Mohs' hardness is 6. The calculated density is 7.1 g/cm 3 . Iwashiroite (Y) occurs as an aggregate of small euhedral platy crystals with a metamict substance in the main ore body of the granite pegmatite mine at the locality. Associated minerals are quartz, microcline and annite. The crystal structure was refined to R = 0.034 with single crystal XRD data. Although the structure consists of TaO 6 octahedra and YO 8 polyhedra, iwashiroite (Y) is not isostructural with fergusonite beta (Y).
doi:10.2465/jmps.101.170 fatcat:zyqillic65go7i5zjljkoxfjie