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Lipuite, a new manganese phyllosilicate mineral from the N'Chwaning III Mine, Kalahari manganese fields, South Africa

Gu Xiangping, Hexiong Yang, Xie Xiande, Jaco J. Van Nieuwenhuizen, Robert T. Downs and Stanley H. Evans
Lipuite, a new manganese phyllosilicate mineral from the N'Chwaning III Mine, Kalahari manganese fields, South Africa
Mineralogical Magazine (October 2019) 83 (5): 645-654

Abstract

A new phyllosilicate mineral, lipuite (IMA2014-085), has been discovered from the N'Chwaning III mine, Kalahari Manganese Fields, Northern Cape Province, Republic of South Africa. It occurs as platy, tabular, or granular crystals and veined agglomerate in association with Mn-bearing sugilite, taniajacoite, pectolite, richterite, norrishite and namansilite. Lipuite is dark red-brown with vitreous lustre, red streak, an estimated Mohs hardness of 5 and the measured density is 2.83(3) g/cm (super 3) . It is biaxial (+) and characterised by bright red to dark red colour in thin section with measured refractive indices in white light: alpha =1.635(1), beta =1.653(1), gamma =1.670(1) and 2V=86(2) degrees . The Raman spectra of lipuite are composed of over 21 bands at 109, 146, 162, 183, 206, 244, 288, 342, 362, 455, 496, 520, 552, 613, 669, 886, 930, 971, 1097, 3487 and 3540 cm (super -1) . The empirical formula from microprobe analyses is (based on total number of cations=27.5 and structural refinement): K (sub 1.12) Na (sub 8.16) (Mn (sub 4.77) Fe (sub 0.07) ) (sub Sigma 4.84) Mg (sub 0.44) [Si (sub 11.97) O (sub 30) (OH) (sub 4) ](PO (sub 4) ) (sub 0.94) O (sub 2) (OH) (sub 2) .4H (sub 2) O. The idealised formula is: KNa (sub 8) Mn (super 3+) (sub 5) Mg (sub 0.5) [Si (sub 12) O (sub 30) (OH) (sub 4) ](PO (sub 4) )O (sub 2) (OH) (sub 2) .4H (sub 2) O. Lipuite is orthorhombic, space group Pnnm, a=9.080(3), b=12.222(3), c=17.093(5) Aa, V=1897.0(9) Aa (super 3) and Z=2. The strongest powder X-ray diffraction peaks [d, Aa (I)(hkl)] are: 9.965(40)(011), 2.938(33)(310), 2.895(100)(311), 2.777(38)(224), 2.713(53)(320), 2.483(32)(126), 2.086(35)(046) and 1.534(40)(446). The crystal structure of lipuite is characterised by sheets of SiO (sub 4) tetrahedra that are linked together along [010] by K (super +) , Na (super +) , Mn (super 3+) , Mg (super 2+) and P (super 5+) cations, as well as hydrogen bonds. These tetrahedral sheets consist of 14-membered rings of SiO (sub 4) tetrahedra that zigzag along [100]. The two independent Mn (super 3+) cations are both octahedrally coordinated. They form five-membered, edge-shared octahedral clusters between the SiO (sub 4) tetrahedral sheets. Lipuite represents a rather unique structure type and its silicate tetrahedral sheets can be considered a derivative of the silicate sheets in mica.


ISSN: 0026-461X
EISSN: 1471-8022
Serial Title: Mineralogical Magazine
Serial Volume: 83
Serial Issue: 5
Title: Lipuite, a new manganese phyllosilicate mineral from the N'Chwaning III Mine, Kalahari manganese fields, South Africa
Affiliation: Central South University, School of Geosciences and Info-Physics, Changsha, China
Pages: 645-654
Published: 201910
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 40
Accession Number: 2020-006727
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 8 tables
S27°07'51" - S27°07'51", E22°50'29" - E22°50'29"
Secondary Affiliation: University of Arizona, USA, United StatesChinese Academy of Sciences, Guangzhou Institute of Geochemistry, CHN, China
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 202006
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