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Minohlite, a new copper-zinc sulfate mineral from Minoh, Osaka, Japan

Published online by Cambridge University Press:  05 July 2018

M. Ohnishi*
Affiliation:
12-43 Takehana Ougi-cho, Yamashina-ku, Kyoto 607-8082, Japan
N. Shimobayashi
Affiliation:
Department of Geology and Mineralogy, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
D. Nishio-Hamane
Affiliation:
The Institute for Solid State Physics (ISSP), The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
K. Shinoda
Affiliation:
Department of Geosciences, Faculty of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
K. Momma
Affiliation:
Department of Geology and Paleontology, The National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan
T. Ikeda
Affiliation:
Research Center for Compact Chemical System, National Institute of Advanced Industrial Science and Technology (AIST), 4-2-1 Nigatake, Miyagino-ku, Sendai, Miyagi 983-8551, Japan

Abstract

Minohlite, a new copper-zinc sulfate mineral related to schulenbergite, was found in the oxidized zone of the Hirao mine at Minoh (Minoo) City, Osaka Prefecture, Japan. The mineral occurs in cracks in altered shale as rosette aggregates up to 100 m m in diameter, composed of hexagonal platy crystals up to 50 μm m in diameter and 10 μm m in thickness. The associated minerals are chamosite, muscovite, smithsonite, serpierite, ramsbeckite, 'limonite' and chalcopyrite. Minohlite has hexagonal (or trigonal) symmetry with unit-cell parameters of a = 8.2535(11), c = 8.1352(17) Å, V = 479.93(16) Å3 and Z = 1, and possible space groups P6, P, P6/m, P22, P6mm, P2m and P6/mmm (or P3, P3, P321, P3m1, Pm1, P312, P31m and P1m). The six strongest reflections in the powder X-ray diffraction pattern [d in Å (I) hkl] are 8.138 (20) 001; 4.128 (24) 110; 2.702 (100) 120; 2.564 (76) 121; 1.560 (43) 140; and 1.532 (24) 141. Electron microprobe analyses gave the following values (wt.%): CuO 37.18, ZnO 21.08, FeO 0.49, SO3 16.78, SiO2 0.44, and H2O 24.03 (by difference). The empirical formula, calculated on the basis of Cu + Zn + Fe + S + Si = 9 atoms per formula unit, is (Cu4.43Zn2.45Fe0.06)Σ6.94[(SO4)1.99(SiO4)0.07]Σ2.06(OH)9.64·7.81H2O, which leads a simplified formula of (Cu,Zn)7(SO4)2(OH)10·8H2O where Cu > Zn. The mineral is bluish-green and transparent with a pearly to vitreous lustre. The streak is pale green. Cleavage is perfect on {001}. The Mohs hardness number is less than 2. The calculated density is 3.28 g cm−3. The mineral is named after Minoh City, where it was discovered.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2013

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