- 著者
-
HORI Hidemichi
KOBAYASHI Toshinori
MIYAWAKI Ritsuro
MATSUBARA Satoshi
YOKOYAMA Kazumi
SHIMIZU Masaaki
- 出版者
- 日本鉱物科学会
- 雑誌
- Journal of mineralogical and petrological sciences (ISSN:13456296)
- 巻号頁・発行日
- vol.101, no.4, pp.170-177, 2006-08-01
- 被引用文献数
-
1
8
Iwashiroite-(Y), YTaO<sub>4</sub>, was found from Suishoyama, Kawamata Town, Fukushima Prefecture, Japan. It is monoclinic</i>, <i>P</i>2/<i>a</i>, <i>a</i> = 5.262(5) Å, <i>b</i> = 5.451(5) Å, <i>c</i> = 5.110(5) Å, β = 95.12(10)°, <i>V</i> = 146.0(2) Å<sup>3</sup>, Z = 2. The five strongest lines in the powder XRD pattern [<i>d</i>(Å), <i>I</i>/<i>I</i><sub>0</sub>, <i>hkl</i>] are (3.13, 100, 111), (2.95, 94, 111), (2.73, 26, 020), (1.890, 29, 220) and (1.862, 29, 022). Electron microprobe analysis gave; Y<sub>2</sub>O<sub>3</sub> 29.10, Ce<sub>2</sub>O<sub>3</sub> 0.10, Nd<sub>2</sub>O<sub>3</sub> 0.10, Sm<sub>2</sub>O<sub>3</sub> 0.36, Gd<sub>2</sub>O<sub>3</sub> 1.06, Tb<sub>2</sub>O<sub>3</sub> 0.25, Dy<sub>2</sub>O<sub>3</sub> 2.38, Ho<sub>2</sub>O<sub>3</sub> 0.56, Er<sub>2</sub>O<sub>3</sub> 2.09, Tm<sub>2</sub>O<sub>3</sub> 0.37, Yb<sub>2</sub>O<sub>3</sub> 3.33, Lu<sub>2</sub>O<sub>3</sub> 0.85, ThO<sub>2</sub> 0.02, UO<sub>2</sub> 0.15, CaO 0.17, Ta<sub>2</sub>O<sub>5</sub> 40.64, Nb<sub>2</sub>O<sub>5</sub> 16.66, TiO<sub>2</sub> 0.41, total 98.60 wt%, and leads to the empirical formula, (Y<sub>0.81</sub>Yb<sub>0.05</sub>Dy<sub>0.04</sub>Er<sub>0.03</sub></sub>Gd<sub>0.02</sub>Lu<sub>0.01</sub>Ho<sub>0.01</sub>Sm<sub>0.01</sub>Ca<sub>0.01</sub>Tm<sub>0.01</sub>)<sub>Σ1.00</sub>(Ta<sub>0.58</sub>Nb<sub>0.39</sub>T<sub>i0.02</sub>)<sub>Σ0.99</sub>O<sub>4</sub> on the basis of the 4 oxygen atoms per formula unit. Iwashiroite-(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<sup>3</sup>. 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 <i>R</i> = 0.034 with single crystal XRD data. Although the structure consists of TaO<sub>6</sub> octahedra and YO<sub>8</sub> polyhedra, iwashiroite-(Y) is not isostructural with fergusonite-beta-(Y).