R1: Characterization and description of minerals (Joint Session with The Gemmological Society of Japan)

12:30 PM - 2:00 PM JST(3:30 AM - 5:00 AM UTC)

[R1P-23] Fraipontite from the Ikuno mine, Hyogo Prefecture, Japan

*Masayuki OHNISHI¹, Norimasa Shimobayashi^2,3, Keiji Shinoda⁴, Masaki Takaya², Daisuke Nishio-Hamane⁵ (1. Non, 2. Kyoto Univ., 3. Masutomi Mus. of Geosci., 4. Osaka Metro. Univ., 5. Univ. of Tokyo)

Keywords:

Fraipontite,Kaolinite-serpentine group,Clay mineral,Ikuno mine

Fraipontite was found from the dump of Keiju vein, Kanagase vein group in the Ikuno mine, Hyogo Prefecture, Japan. The mineral occurs as botryoidal aggregates (up to 0.5 mm in diameter) of platy crystals up to 80 μm across and 3 μm thick in crack of quartz and “limonite”. The associated minerals are “wad” and hemimorphite. The mineral is white to pale blue with a pearly luster. The refractive indices were α = 1.618(2) and γ = 1.622(2). The density was 3.00(3) g/cm³. EPMA analyses (WDS mode) gave the empirical formula (Zn_2.19Cu_0.16Fe_0.03Al_0.66)_Σ3.04(Si_1.27Al_0.7)_Σ2.00O₅(OH)₄. Powder X-ray diffraction pattern [d Å (I) hkl] collected with a Gandolfi camera were 7.09 (100) 002, 4.620 (5) 020, 3.548 (61) 004, 2.649 (21) -201, 2.499 (12) 211, 2.387 (16) -203, 2.262 (5) 221, 2.128 (3) -214, 2.002 (7) -205, 1.770 (6) 008, 1.662 (6) -207, 1.540 (13) 060, 1.505 (7) 251, and 1.413 (7) 064. The indexing of the powder pattern was based on ICDD-PDF 14-366. The refined unit-cell parameters were a = 5.343(5), b = 9.242(4), c = 14.19(2) Å, and β = 93.40(9)°.

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