Fluorluanshiweiite, KLiAl1.5□0.5(Si3.5Al0.5)O10F2, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, China

A new mineral species of the mica group, fluorluanshiweiite, ideally KLiAl1.5□0.5(Si3.5Al0.5)O10F2, has been found in the Nanyangshan LCT (Li, Cs, Ta) pegmatite d...

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Main Authors:	Kai Qu, Xianzhang Sima, Guowu Li, Guang Fan, Ganfu Shen, Xing Liu, Zhibin Xiao, Hu Guo, Linfei Qiu, Yanjuan Wang
Format:	Article
Language:	English
Published:	MDPI AG 2020-01-01
Series:	Minerals
Subjects:	fluorluanshiweiite mica group new mineral species chemical composition crystal structure north qinling orogen china
Online Access:	https://www.mdpi.com/2075-163X/10/2/93

id	doaj-a9b1d30a1e4d49db8a014c7ce3c52718
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spelling	doaj-a9b1d30a1e4d49db8a014c7ce3c527182020-11-25T02:06:04ZengMDPI AGMinerals2075-163X2020-01-011029310.3390/min10020093min10020093Fluorluanshiweiite, KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, ChinaKai Qu0Xianzhang Sima1Guowu Li2Guang Fan3Ganfu Shen4Xing Liu5Zhibin Xiao6Hu Guo7Linfei Qiu8Yanjuan Wang9Tianjin Center, China Geological Survey, Tianjin 300170, ChinaTianjin Center, China Geological Survey, Tianjin 300170, ChinaCrystal Structure Laboratory, China University of Geosciences (Beijing), Beijing 100083, ChinaBeijing Research Institute of Uranium Geology, Beijing 100029, ChinaChengdu Center, China Geological Survey, Chengdu 610081, ChinaTianjin Center, China Geological Survey, Tianjin 300170, ChinaTianjin Center, China Geological Survey, Tianjin 300170, ChinaTianjin Center, China Geological Survey, Tianjin 300170, ChinaBeijing Research Institute of Uranium Geology, Beijing 100029, ChinaCrystal Structure Laboratory, China University of Geosciences (Beijing), Beijing 100083, ChinaA new mineral species of the mica group, fluorluanshiweiite, ideally KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>, has been found in the Nanyangshan LCT (Li, Cs, Ta) pegmatite deposit in North Qinling Orogen (NQO), central China. Fluorluanshiweiite can be regarded as the F-dominant analogue at the <i>A</i> site of luanshiweiite or the K-dominant analogue at the <i>I</i> site of voloshinite. It appears mostly in cookeite as a flaky residue, replaced by Cs-rich mica, or in the form of scale aggregates. Most individual grains are <1 mm in size, with the largest being ca. 1 cm, and the periphery is replaced by cookeite. No twinning is observed. The mineral is silvery white as a hand specimen, and in a thin section, it appears grayish-white to colorless, transparent with white streaks, with vitreous luster and pearliness on cleavage faces. It is flexible with micaceous fracture; the Mohs hardness is approximately 3; the cleavage is perfect on {001}; and no parting is observed. The measured and calculated densities are 2.94(3) and 2.898 g/cm<sup>3</sup>, respectively. Optically, fluorluanshiweiite is biaxial (−), with α = 1.554(1), β = 1.581(1), γ = 1.583(1) (white light), 2<i>V</i>(meas.) = 25° to 35°, 2<i>V</i>(calc.) = 30.05°. The calculated compatibility index based on the empirical formula is −0.014 (superior). An electron microprobe analysis yields the empirical formula calculated based on 10 O atoms and 2 additional anions of (K<sub>0.85</sub>Rb<sub>0.12</sub>Cs<sub>0.02</sub>Na<sub>0.03</sub>)<sub>Σ1.02</sub>[Li<sub>1.05</sub>Al<sub>1.44</sub>(□<sub>0.47</sub>Fe<sub>0.01</sub>Mn<sub>0.02</sub>)<sub>Σ0.5</sub>] <sub>Σ2.99</sub>(Si<sub>3.55</sub>Al<sub>0.45</sub>) <sub>Σ4</sub>O<sub>10</sub>F<sub>2</sub>, which can be simplified to KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>. Fluorluanshiweiite is monoclinic with the space group <i>C</i>2/<i>m</i> and unit cell parameters <i>a</i> = 5.2030(5), <i>b</i> = 8.9894(6), <i>c</i> = 10.1253(9) Å, <i>β</i> = 100.68(1)°, and <i>V</i> = 465.37(7) Å<sup>3</sup>. The strongest eight lines in the X-ray diffraction data are [<i>d</i> in Å(<i>I</i>)(hkl)]: 8.427(25) (001), 4.519(57) (020), 4.121(25) (021), 3.628(61) (<span style="text-decoration: overline;">1</span>12), 3.350(60) (022), 3.091(46) (112), 2.586(100) (<span style="text-decoration: overline;">1</span>30), and 1.506(45) (312).https://www.mdpi.com/2075-163X/10/2/93fluorluanshiweiitemica groupnew mineral specieschemical compositioncrystal structurenorth qinling orogenchina
collection	DOAJ
language	English
format	Article
sources	DOAJ
author	Kai Qu Xianzhang Sima Guowu Li Guang Fan Ganfu Shen Xing Liu Zhibin Xiao Hu Guo Linfei Qiu Yanjuan Wang
spellingShingle	Kai Qu Xianzhang Sima Guowu Li Guang Fan Ganfu Shen Xing Liu Zhibin Xiao Hu Guo Linfei Qiu Yanjuan Wang Fluorluanshiweiite, KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, China Minerals fluorluanshiweiite mica group new mineral species chemical composition crystal structure north qinling orogen china
author_facet	Kai Qu Xianzhang Sima Guowu Li Guang Fan Ganfu Shen Xing Liu Zhibin Xiao Hu Guo Linfei Qiu Yanjuan Wang
author_sort	Kai Qu
title	Fluorluanshiweiite, KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, China
title_short	Fluorluanshiweiite, KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, China
title_full	Fluorluanshiweiite, KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, China
title_fullStr	Fluorluanshiweiite, KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, China
title_full_unstemmed	Fluorluanshiweiite, KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, China
title_sort	fluorluanshiweiite, klial<sub>1.5</sub>□<sub>0.5</sub>(si<sub>3.5</sub>al<sub>0.5</sub>)o<sub>10</sub>f<sub>2</sub>, a new mineral of the mica group from the nanyangshan lct pegmatite deposit, north qinling orogen, china
publisher	MDPI AG
series	Minerals
issn	2075-163X
publishDate	2020-01-01
description	A new mineral species of the mica group, fluorluanshiweiite, ideally KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>, has been found in the Nanyangshan LCT (Li, Cs, Ta) pegmatite deposit in North Qinling Orogen (NQO), central China. Fluorluanshiweiite can be regarded as the F-dominant analogue at the <i>A</i> site of luanshiweiite or the K-dominant analogue at the <i>I</i> site of voloshinite. It appears mostly in cookeite as a flaky residue, replaced by Cs-rich mica, or in the form of scale aggregates. Most individual grains are <1 mm in size, with the largest being ca. 1 cm, and the periphery is replaced by cookeite. No twinning is observed. The mineral is silvery white as a hand specimen, and in a thin section, it appears grayish-white to colorless, transparent with white streaks, with vitreous luster and pearliness on cleavage faces. It is flexible with micaceous fracture; the Mohs hardness is approximately 3; the cleavage is perfect on {001}; and no parting is observed. The measured and calculated densities are 2.94(3) and 2.898 g/cm<sup>3</sup>, respectively. Optically, fluorluanshiweiite is biaxial (−), with α = 1.554(1), β = 1.581(1), γ = 1.583(1) (white light), 2<i>V</i>(meas.) = 25° to 35°, 2<i>V</i>(calc.) = 30.05°. The calculated compatibility index based on the empirical formula is −0.014 (superior). An electron microprobe analysis yields the empirical formula calculated based on 10 O atoms and 2 additional anions of (K<sub>0.85</sub>Rb<sub>0.12</sub>Cs<sub>0.02</sub>Na<sub>0.03</sub>)<sub>Σ1.02</sub>[Li<sub>1.05</sub>Al<sub>1.44</sub>(□<sub>0.47</sub>Fe<sub>0.01</sub>Mn<sub>0.02</sub>)<sub>Σ0.5</sub>] <sub>Σ2.99</sub>(Si<sub>3.55</sub>Al<sub>0.45</sub>) <sub>Σ4</sub>O<sub>10</sub>F<sub>2</sub>, which can be simplified to KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>. Fluorluanshiweiite is monoclinic with the space group <i>C</i>2/<i>m</i> and unit cell parameters <i>a</i> = 5.2030(5), <i>b</i> = 8.9894(6), <i>c</i> = 10.1253(9) Å, <i>β</i> = 100.68(1)°, and <i>V</i> = 465.37(7) Å<sup>3</sup>. The strongest eight lines in the X-ray diffraction data are [<i>d</i> in Å(<i>I</i>)(hkl)]: 8.427(25) (001), 4.519(57) (020), 4.121(25) (021), 3.628(61) (<span style="text-decoration: overline;">1</span>12), 3.350(60) (022), 3.091(46) (112), 2.586(100) (<span style="text-decoration: overline;">1</span>30), and 1.506(45) (312).
topic	fluorluanshiweiite mica group new mineral species chemical composition crystal structure north qinling orogen china
url	https://www.mdpi.com/2075-163X/10/2/93
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Fluorluanshiweiite, KLiAl<sub>1.5</sub>□<sub>0.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>F<sub>2</sub>, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, China

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