Tanohataite, LiMn_2Si_3O_8(OH) : a new mineral from the Tanohata mine, Iwate Prefecture, Japan

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Abstract

Tanohataite, LiMn<sub>2</sub>Si<sub>3</sub>O<sub>8</sub>(OH), the Li analogue of serandite, has been found in a metamorphosed manganese ore deposit of the Tanohata mine, Iwate Prefecture, Japan. The mineral has the triclinic space group <i>P</i>1 with <i>a</i> = 7.612(7), <i>b</i> = 7.038(4), <i>c</i> = 6.700(4) Å, <i>α</i> = 90.23(6)°, <i>β</i> = 94.70(7)°, <i>γ</i> = 105.26 (8)°, <i>V</i> =345.0(3) Å<sup>3</sup>, and <i>Z</i> = 2. The seven strongest lines in the X-ray powder diffraction pattern are [<i>d</i>(Å), (<i>I</i>), (<i>hkl</i>)]: 6.64(35)(001), 3.67(26)(200), 3.13(89)(102), 3.11(69)(211), 2.95(100)(102), 2.81(33)(120), and 2.18(40)(103). Electron microprobe analysis and laser ablation microprobe-inductively coupled plasma-mass spectrometry gave an SiO<sub>2</sub> content of 51.97; MnO, 37.99; MgO, 1.06; CaO, 0.41; Na<sub>2</sub>O, 1.97; Li<sub>2</sub>O, 3.34; total, 96.74 wt%, corresponding to an empirical formula of (Li<sub>0.78</sub>Na<sub>0.22</sub>)<sub>Σ1.00</sub>(Mn<sub>1.86</sub>Ca<sub>0.03</sub>Mg<sub>0.09</sub>)<sub>Σ1.98</sub>Si<sub>3.01</sub>O<sub>8</sub>(OH) on the basis of O = 9. Tanohataite is transparent and pinkish white with a vitreous and silky luster. The streak is white. The cleavage is perfect on {001} and {100}. On the Mohs' scale, the hardness is 5-5<sup>1</sup>/<sub>2</sub>. The calculated density is 3.33 g/cm<sup>3</sup>. Optically, tanohataite is biaxial positive with 2<i>V</i><sub>calc</sub> = 82(2)°, <i>α</i> = 1.593(3), <i>β</i> = 1.618(3), and <i>γ</i> = 1.653(3). Tanohataite occurs as an aggregation of fibrous crystals in veinlets composed mainly of quartz, aegirine, Mn-arfvedsonite, nambulite, natronambulite, and barite.

Journal

  • Journal of Mineralogical and Petrological Sciences

    Journal of Mineralogical and Petrological Sciences 107(3), 149-154, 2012-06-01

    Japan Association of Mineralogical Sciences

References:  25

Codes

  • NII Article ID (NAID)
    10030499275
  • NII NACSIS-CAT ID (NCID)
    AA11460926
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    13456296
  • Data Source
    CJP  J-STAGE 
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