Abstract
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 deposit in North Qinling Orogen (NQO), central China. Fluorluanshiweiite can be regarded as the F-dominant analogue at the A site of luanshiweiite or the K-dominant analogue at the 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/cm3, respectively. Optically, fluorluanshiweiite is biaxial (–), with α = 1.554(1), β = 1.581(1), γ = 1.583(1) (white light), 2V(meas.) = 25° to 35°, 2V(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 (K0.85Rb0.12Cs0.02Na0.03)Σ1.02[Li1.05Al1.44(□0.47Fe0.01Mn0.02)Σ0.5] Σ2.99(Si3.55Al0.45) Σ4O10F2, which can be simplified to KLiAl1.5□0.5(Si3.5Al0.5)O10F2. Fluorluanshiweiite is monoclinic with the space group C2/m and unit cell parameters a = 5.2030(5), b = 8.9894(6), c = 10.1253(9) Å, β = 100.68(1)°, and V = 465.37(7) Å3. The strongest eight lines in the X-ray diffraction data are [d in Å(I)(hkl)]: 8.427(25) (001), 4.519(57) (020), 4.121(25) (021), 3.628(61) (112), 3.350(60) (022), 3.091(46) (112), 2.586(100) (130), and 1.506(45) (312).
Highlights
A new mineral species of the mica group, KLiAl1.5 0.5 (Si3.5 Al0.5 )O10 F2, has been found in the Nanyangshan LCT pegmatite deposit in North Qinling Orogen (NQO), Central China (33◦ 520 58” N, Minerals 2020, 10, 93; doi:10.3390/min10020093 www.mdpi.com/journal/minerals Minerals 2 of 12 2 of 11110◦ 430 55” E)
It is named fluorluanshiweiite based on its relationship to luanshiweiite
This paper describes the physical, andcollection spectroscopic data of fluorluanshiweiite and its
Summary
A new mineral species of the mica group, KLiAl1.5 0.5 (Si3.5 Al0.5 )O10 F2 , has been found in the Nanyangshan LCT pegmatite deposit in North Qinling Orogen (NQO), Central China It is named fluorluanshiweiite based on its relationship to luanshiweiite. A new mineral species of the mica group, KLiAl1.5□0.5(Si3.5Al0.5)O10F2, has been found as F-dominant at the. Nanyangshan LCT pegmatite deposit in North Qinling Orogen (NQO), Central China It is has named on its relationship to luanshiweiite. This paper describes the physical, andcollection spectroscopic data of fluorluanshiweiite and its. This paper describes the physical, chemical, and spectroscopic data of fluorluanshiweiite and its crystal structure
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