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GEOREF RECORD

Murakamiite, LiCa (sub 2) Si (sub 3) O (sub 8) (OH), a Li-analogue of pectolite, from the Iwagi Islet, southwest Japan

Teruyoshi Imaoka, Mariko Nagashima, Takashi Kano, Jun-Ichi Kimura, Qing Chang and Chihiro Fukuda
Murakamiite, LiCa (sub 2) Si (sub 3) O (sub 8) (OH), a Li-analogue of pectolite, from the Iwagi Islet, southwest Japan
European Journal of Mineralogy (September 2017) 29 (6): 1045-1053

Abstract

Murakamiite (IMA2016-066), ideally LiCa (sub 2) Si (sub 3) O (sub 8) (OH), is a new mineral that was recently discovered in an aegirine-augite albitite exposed on the Iwagi Islet, Ehime Prefecture, Japan. It occurs as prismatic crystals and monomineralic aggregates up to 1.7 mm long, is white to colourless with a white streak, and has a vitreous to silky lustre. It has a Mohs hardness of 41/2-5 and is brittle with a splintery fracture and perfect {100} and {001} cleavage. Measured and calculated densities are D (sub meas) = 2.86(1) and D (sub calc) = 2.85(1) g.cm (super -3) , respectively. Murakamiite is optically biaxial (+) and non-pleochroic, with refractive indices (in white light) of alpha = 1.602(1), beta = 1.611(1), gamma = 1.643(1), and with 2V (sub meas) = 56-59(2) degrees and 2V (sub calc) = 57 degrees . Dispersion is weak, with r > v. The optical orientation is X^c 10-11 degrees , Y^a 10-14 degrees , Z^b 0-5 degrees . Murakamiite is triclinic, belonging to space group P1 (super -) with the unit-cell parameters a = 7.9098(2) A, b = 7.0320(2) A, c = 6.9863(2) A, alpha = 90.596(2) degrees , beta = 95.589(2) degrees , gamma = 102.767(2) degrees , V = 376.98(2) A (super 3) (Z = 2). The eight strongest lines in the X-ray powder diffraction pattern are [d (sub obs) /A(I)(h k l)]: 2.897(100)(22 (super -) 0), 3.055(49)(012, 102, 11 (super -) 2 (super -) ), 3.295(41) (102 (super -) ), 3.225(33)(201), 3.845(20)(200), 2.284(19)(103 (super -) ), 2.720(15)(121 (super -) , 22 (super -) 1, 202 (super -) ), and 6.962(15)(001). The chemical composition is (average of sixteen analyses by LA-ICP-MS, H (sub 2) O by TG-DTA, wt%): SiO (sub 2) 54.94, Al (sub 2) O (sub 3) 0.01, FeO 0.38, MnO 0.80, MgO 0.04, CaO 34.14, Na (sub 2) O 4.37, Li (sub 2) O 2.52 and H (sub 2) O 2.80. The empirical formula of murakamiite, based on 9 O apfu, is (Li (sub 0.55) Na (sub 0.46) ) (sub Sigma 1.01) (Ca (sub 1.98) Mn (sub 0.04) Fe (sub 0.02) ) (sub Sigma 2.04) Si (sub 2.98) O (sub 8) (OH) (sub 1.01) ; thus, muakamiite is a H-bearing pyroxenoid with three-periodicity of SiO (sub 4) tetrahedra and the Li-analogue of pectolite. The species is named in honour of the late Professor Emeritus Nobuhide Murakami (1923-1994) of Yamaguchi University, Japan. Type specimens are housed in the National Museum of Nature and Science, Tsukuba, Japan, and the Geological and Mineralogical Museum of Faculty of Science, Yamaguchi University, Japan.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 29
Serial Issue: 6
Title: Murakamiite, LiCa (sub 2) Si (sub 3) O (sub 8) (OH), a Li-analogue of pectolite, from the Iwagi Islet, southwest Japan
Affiliation: Yamaguchi University, Graduate School of Sciences and Technology for Innovation, Yamaguchi, Japan
Pages: 1045-1053
Published: 20170905
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 39
Accession Number: 2017-085929
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
N34°15'40" - N34°15'40", E133°08'47" - E133°08'47"
Secondary Affiliation: Japan Agency for Marine-Earth Science and Technology, JPN, JapanGem Research Japan, JPN, Japan
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201745
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