Fluorluanshiweiite, KLiAl_1.5□_0.5(Si_3.5Al_0.5)O₁₀F₂, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, China

Abstract

A new mineral species of the mica group, fluorluanshiweiite, ideally KLiAl_1.5□_0.5(Si_3.5Al_0.5)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 (K_0.85Rb_0.12Cs_0.02Na_0.03)_Σ1.02[Li_1.05Al_1.44(□_0.47Fe_0.01Mn_0.02)_Σ0.5] _Σ2.99(Si_3.55Al_0.45) _Σ4O₁₀F₂, which can be simplified to KLiAl_1.5□_0.5(Si_3.5Al_0.5)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) ų. 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).

1. Introduction

A new mineral species of the mica group, KLiAl_1.5□_0.5(Si_3.5Al_0.5)O₁₀F₂, has been found in the Nanyangshan LCT pegmatite deposit in North Qinling Orogen (NQO), Central China (33°52′58″ N, 110°43′55″ E). It is named fluorluanshiweiite based on its relationship to luanshiweiite. It is characterized as F-dominant at the A site of luanshiweiite [1] or K-dominant at the I site of voloshinite [2]. The new mineral (IMA2019-053) has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA-CNMNC) [3]. The material was deposited in the mineralogical collection of the Geological Museum of China, No. 16, Xisi Yangrou Hutong, Xicheng District, Beijing 100034, People’s Republic of China (catalogue number: M16085). This paper describes the physical, chemical, and spectroscopic data of fluorluanshiweiite and its crystal structure.

2. Occurrence and Physical Properties

The Nanyangshan rare metal deposit is located in NQO, Western Henan Province, central China. The rare metal mineralization is hosted in granitic pegmatite [4]. According to the classification and revision by Černý [5] and Černý and Ercit [6], it is classified as LCT pegmatite. The Ar-Ar dating of muscovite revealed that the Nanyangshan pegmatite formed at 396–410 Ma [7], and the age coincides with the time of U-REE-rare metal mineralization (mean = 408 Ma) in NQO [8,9,10], shortly after 400–428 Ma (mean = 417 Ma), when the related intrusions formed, indicating that the mineral formed in the late stage of the evolution of a pegmatite-forming magmatic liquid. The new mineral is closely associated with luanshiweiite (first recorded locality [1]), polylithionite, cookeite, albite, quartz and an unknown Cs-rich mica (Figure 1a,b), and it is commonly found with spodumene, montebrasite, elbaite, fluorapatite, pollucite, and nanpingite. Tantalite-(Mn), columbite-(Mn), bismutotantalite, stibiotantalite, oxynatromicrolite (first recorded locality [11]), and fluornatromicrolite are some other associated minerals.

Fluorluanshiweiite occurs 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 (Figure 1c,d). The mineral is silvery white as a hand specimen and grayish-white to colorless in a thin section, transparent with white streaks. In addition, it has vitreous luster and appears pearly on cleavage planes. It is flexible with micaceous fracture, the Mohs hardness is approximately 3, the cleavage is perfect on {001}, and no parting was 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 (1-K_P/K_C) is superior (−0.014) [12].

3. Chemical Composition

The chemical compositions of the fluorluanshiweiite and associated luanshiweiite and polylithionite were determined at the Beijing Research Institute of Uranium Geology with a JXA-8100 electron microprobe at 15 kV and 10 nA with a beam diameter of 10 μm. The FKα was determined with an LDE1 crystal (JEOL, 2d ≈ 6 nm), which is suitable for the analysis of ⁶C–¹⁰Ne, and the P/B ratio is much higher than that of the TAP crystal for F. The standards include phlogopite for K, Fe and Al; pollucite for Rb and Cs; albite for Na; tantalite-(Mn) for Mn; sanidine for Si and fluorapatite for F. The fluorine migration and peak overlap have been fully considered in the factors affecting the accurate quantification of F in the EPMA process to ensure that the results are reliable. The lithium content analysis was carried out using an LA-MC-ICP-MS instrument (Neptune, Thermo Fisher Scientific) equipped with a (ESI) NewWare 193 FX ArF Excimer laser ablation system with a 193-nm wavelength. The operating conditions were as follows: beam diameter = 30 μm, alongside a laser pulse rate of 8 Hz with an energy density of approximately 4 J/cm²; N = 20. The obtained results were consistent with the data (3.95% Li₂O) determined by atomic absorption spectroscopy (AAS). Scanning electron microscopy investigations were performed with an FEI Nova Nano scanning electron microscope (SEM) (10 μs; 15 kV). The anhydrous nature of the studied mineral was indicated by the absence of OH stretching vibration absorption in the ATR-FT/IR spectrum, as shown below.

Twenty electron microprobe point analyses for fluorluanshiweiite yielded an average composition (wt. %) of K₂O 9.87, Rb₂O 2.86, Cs₂O 0.86, Na₂O 0.26, FeO 0.26, MnO 0.43, Al₂O₃ 23.65, SiO₂ 52.42, and F 9.35. The Li₂O content analyses yielded an average composition of 3.85 wt % by LA-MC-ICP-MS, resulting in a total of 99.87. The empirical chemical formula calculated on the basis of 10 O²⁻ and 2 F⁻ apfu. is (K_0.85Rb_0.12Cs_0.02Na_0.03) _Σ1.02[Li_1.05Al_1.44(□_0.47Fe_0.01Mn_0.02)_Σ0.5]_Σ2.99(Si_3.55Al_0.45)_Σ4O₁₀F₂. The ideal formula is K(LiAl_1.5□_0.5)(Si_3.5Al_0.5)O₁₀F₂, which requires K₂O 11.88, Li₂O 3.77, Al₂O₃ 25.73, SiO₂ 53.07, F 9.59, O≡F −4.04, total 100 wt. %. Compared to polylithionite in the Nanyangshan LCT deposit, fluorluanshiweiite contains more Rb, less Si and more Al. The high fluorine content is a key feature that distinguishes fluorluanshiweiite from luanshiweiite (

Table 1. Chemical composition (wt. %) of fluorluanshiweiite and other lepidolite species in nanyangshan LCT deposit.

%	Fluorluanshiweiite			Luanshiweiite			Polylithionite
	Mean	apfu	σ †	Mean	apfu	σ	Mean	apfu	σ
K2O	9.87	0.85	0.20	10.58	0.89	0.16	10.88	0.91	0.31
Rb2O	2.86	0.12	0.09	1.41	0.06	0.07	0.76	0.03	0.15
Cs2O	0.86	0.02	0.17	0.21	0.01	0.21	0.65	0.02	0.11
Na2O	0.26	0.03	0.05	0.36	0.05	0.11	0.05	0.01	0.22
Li2O *	3.85	1.05	0.22	3.85	1.02	0.35	7.70	2.04	0.29
FeO	0.26	0.01	0.10	0.08	0.00	0.23	0.00	0.00	0.00
MnO	0.43	0.02	0.18	0.07	0.00	0.15	0.01	0.00	0.17
Al2O3	23.65	1.88	0.57	24.86	1.93	0.65	16.00	1.24	0.45
SiO2	52.42	3.54	0.64	53.45	3.52	0.56	57.95	3.81	0.59
F	9.35	2.00	0.24	1.31	0.27	0.31	9.71	2.02	0.27
F≡O	−3.93			−0.55			−4.08
H2O+				4.07
Total	99.88			99.7			99.63

Notes: * average composition by LA-MC-ICP-MS, others by EPMA. ^† the standard deviation refers to the weight oxides.

).

4. Spectroscopic Features

Spectroscopic analyses were performed at the Beijing Research Institute of Uranium Geology. Infrared spectroscopic data of fluorluanshiweiite were obtained using a Bruker LUMOS spectrometer with an ATR model in the range 600–4000 cm⁻¹. Raman spectra were recorded on a LabRAM HR Raman microscope with a laser excitation wavelength of 532 nm. The power of the excitation radiation was 20 mW, and the lateral resolution was estimated to be 1 μm. The results were acquired in the range 100–2000 cm⁻¹.

4.1. Infrared Spectroscopy

The vibrations of mica group minerals can be roughly separated into the vibrational region of hydroxyl groups and the lattice vibrational region, including the vibrations of Si(Al)O₄ tetrahedra and octahedrally coordinated cations [13]. In the IR spectrum of fluorluanshiweiite (Figure 2), the bands at 747 and 791 cm⁻¹ are due to the Al–O fundamental modes, and the bands at 955, 979, and 1085 cm⁻¹ are due to the Si–O fundamental modes, resembling the spectrum of luanshiweiite (760, 798, 891, 988, and 1115 cm⁻¹) [1] and similar to the infrared spectral reference cards (Sil59, Sil60) of the lepidolite series [14].

There is no evidence for the high-energy OH stretching vibrations that commonly occur in the region from 3750–3550 cm⁻¹ for mica group minerals. The defining characteristic of the infrared spectrum is the absence of the high-energy hydroxyl stretching vibration absorption band at −3620 cm⁻¹ [1], which is the most significant difference between fluorluanshiweiite and luanshiweiite. The chemical analyses confirm that the A site in the new mineral is fully occupied by F (Table 1).

4.2. Raman Spectroscopy

The resulting Raman spectrum of fluorluanshiweiite resembles that of a “Cs-bearing lepidolite” from lepidolite granite, Yichun, China (peaks: 181, 240, 710, and 1141 cm⁻¹) [15], and is similar to the RRUFF Project database spectra of the lepidolite series (X050113, R040101.3, R050132.4). The typical peak for phyllosilicate minerals at ~700 cm⁻¹ is well displayed for fluorluanshiweiite (711 cm⁻¹), corresponding to both Si–O stretching and O–Si–O bending deformations. The peaks at approximately 559 and 1139 cm⁻¹ are attributed to the stretching mode of the Si–O bond in SiO₄ tetrahedra [16,17,18].

Raman spectra of mica minerals show several peaks in the low-wavenumber region: ~100, ~160, ~195, ~220, and ~240 cm⁻¹, of which peaks at ~195 and ~240 cm⁻¹ are generally strong in diocatahedral lepidolite [19]. On the basis of the previous results of Loh [20], the peaks at 182 and 245 cm⁻¹ for fluorluanshiweiite may be assigned to the internal vibrations of the MO₆ octahedron (Figure 3).

5. Crystal Structure

Both powder and single-crystal X-ray diffraction data of fluorluanshiweiite were collected on a Rigaku Oxford diffraction XtaLAB PRO-007HF microfocus rotating anode X-ray source (1.2 kW, MoKα, λ = 0.71073 Å) and a hybrid pixel array detector single-crystal diffractometer using MoKα-radiation in the Laboratory of Crystal Structure, China University of Geosciences (Beijing, China).

X-ray powder diffraction data are given in

Table 2. X-ray powder diffraction data (d in Å) for fluorluanshiweiite (8 strongest lines are in bold).

Imeas	dmeas	dcalc	hkl	Imeas	dmeas	dcalc	hkl
25	8.427	9.956	001	9	2.1984	2.1926	041
57	4.5191	4.4956	020	14	2.1414	2.1386	133
14	4.3396	4.3242	111	3	2.0992	2.0988	221
25	4.1208	4.0975	021	10	1.9959	2.0005	223
14	3.8564	3.8368	111	7	1.957	1.9537	133
61	3.6276	3.6154	112	4	1.7209	1.7237	223
60	3.3495	3.3368	022	11	1.6614	1.6612	242
46	3.091	3.0802	112	16	1.6403	1.6434	116
25	2.8975	2.8904	113	10	1.5824	1.5845	243
17	2.6795	2.6705	023	6	1.5492	1.5494	153
100	2.5859	2.5856	130	45	1.5061	1.507	312
25	2.4571	2.466	131	5	1.3821	1.3778	225
25	2.3903	2.3873	132	10	1.343	1.343	136
17	2.2539	2.2478	040	21	1.298	1.301	316

. The reflection intensities are close to those of the theoretical pattern of lepidolite-1M (database ICDD, card no. 85-911). The strongest eight lines in the X-ray diffraction pattern 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). The powder X-ray diffraction data are reported in Table 2.

A colorless flake of fluorluanshiweiite was selected for the single-crystal X-ray diffraction data collection. All reflections were indexed on the basis of a monoclinic unit cell. The structure was solved and refined using SHELX Software [21] based on the space group C2/m. Unit-cell parameters were as follows: a = 5.2030(5), b = 8.9894(6), c = 10.1253(9) Å, β = 100.68(1)° and V = 465.37(7) ų. Anisotropic refinement using all measured independent data and reflections with Fo ≥ 4σ resulted in an R₁ factor of 0.091. The relatively large R₁ could be due to the crystal quality being imperfect; such values for the R factor are relatively often reported for the lepidolite series. In addition, the high R₁ factor of micas may also be affected by the Durovič effect [22]. The crystal structure refinement details for fluorluanshiweiite are reported in

Table 3. Crystallographic data and refinement results for fluorluanshiweiite.

Crystal Symmetry	Monoclinic
Space group	C2/m
Polytype	1M
a (Å)	5.2030(5)
b (Å)	8.9894(6)
c (Å)	10.1253(9)
β (°)	100.68(1)
V (Å3)	465.37(7)
Z	2
Density(cal.) (g/cm3)	2.898
Radiation type	MoKα
2θmax (°)	60
total reflections	1255
independent reflections	577
reflections with Fo ≥ 4σ	516
Final R1	0.091
wR2 factors	0.202
Goodness-of-fit	1.318
Largest diff. peak and hole (e−/Å3)	1.203–0.815

. A view of the structure is presented in Figure 4. Refined coordinates and anisotropic-displacement parameters are presented in

Table 4. Atomic coordinates and isotropic displacement parameters (in Ų) for fluorluanshiweiite.

Atom	Wyck.	s.o.f.	x	y	z	Ueq
K1	2d	0.85	0	1/2	1/2	0.0306(9)
Rb1	2d	0.12	0	1/2	1/2	0.0306(9)
Li1	2a		1/2	1/2	0	0.0160(5)
Al1	4g	0.71	1/2	0.8277(5)	0	0.0206(11)
Si1	8j	0.88	0.4185(4)	0.6681(2)	0.2673(2)	0.0185(6)
Al2	8j	0.12	0.4185(4)	0.6681(2)	0.2673(2)	0.0185(6)
O1	4i		0.4722(19)	1/2	0.3264(9)	0.0270(2)
O2	8j		0.6769(11)	0.7649(7)	0.3313(6)	0.0258(13)
O3	8j		0.3605(11)	0.6759(6)	0.1056(6)	0.0229(13)
F1	4i		0.8921(16)	1/2	0.0994(8)	0.0470(2)

Notes: I site is fixed by 0.85K + 0.12Rb, M2 site is fixed by 0.71Al and T site is fixed by 0.88Si + 0.12Al.

and

Table 5. Anisotropic displacement parameters (in Ų) for fluorluanshiweiite.

Atom	U11	U22	U33	U12	U13	U23
K1	0.0279(18)	0.0253(17)	0.040(2)	0.00000	0.0088(15)	0.00000
Rb1	0.0279(18)	0.0253(17)	0.040(2)	0.00000	0.0088(15)	0.00000
Li1	0.011(11)	0.013(12)	0.028(13)	0.00000	0.013(10)	0.00000
Al1	0.018(2)	0.016(2)	0.029(2)	0.00000	0.0080(19)	0.00000
Si1	0.0147(11)	0.0133(11)	0.0286(11)	−0.0006(7)	0.0067(8)	0.0018(8)
Al2	0.0147(11)	0.0133(11)	0.0286(11)	−0.0006(7)	0.0067(8)	0.0018(8)
O1	0.037(5)	0.012(4)	0.033(5)	0.00000	0.006(4)	0.00000
O2	0.016(3)	0.028(3)	0.035(3)	−0.008(2)	0.009(2)	−0.002(3)
O3	0.022(3)	0.015(3)	0.034(3)	−0.001(2)	0.011(2)	−0.001(2)
F1	0.025(4)	0.088(8)	0.030(4)	0.00000	0.008(3)	0.00000

, and selected bond lengths and angles are given in

Table 6. Selected bond lengths (Å) and angles (°) for fluorluanshiweiite.

K1—O1	2.973(9) × 2	Al1—O3	1.955(8) × 2
K1–O1′	3.275(10) × 2	Al1–O3′	1.979(6) × 2
K1–O2	2.969(6) × 4	Al1–F1	1.984(7) × 2
K1–O2′	3.218(6) × 4	<M2–O>	1.973
<I–O> inner	2.970	Si1–O1	1.631(4)
<I–O> outer	3.237	Si1–O2	1.631(8)
Li1–O3	2.112(6) × 4	Si1–O2’	1.632(6)
Li1–F1	2.101(8) × 2	Si1–O3	1.610(6)
<M1–O>	2.108	<T–O>	1.626
O1i–K1–O2i	49.56(10)	Si1–O1–K1ii	107.25(7)
O2i–K1–O1	94.95(10)	Si1–O1–K1	95.63(7)
F1–Li1–O3	98.74(16)	K1ii–O1–K1	112.58(29)
F1–Li1–O3	81.3(2)	Si1–O2–K1ii	97.19(24)
O3–Si1–O2	111.35(32)	Si1–O3–Al1	124.83(34)
O3–Si1–O1	113.76(23)	Si1–O3–Li1	117.43(32)
O2–Si1–O1	105.99(24)	Al1–O3–Li1	92.79(22)

Symmetry codes: (i) −1 + x, y, z; (ii) 1 + x, y, z.

.

6. Discussion

The structure of fluorluanshiweiite is similar to that of other species of the mica group. The general formula of mica group minerals may be written as IM_2–3□₁₋₀T₄O₁₀A₂ [23]; for fluorluanshiweiite, I is K, M is Li + 1.5Al + 0.5□, T is 3.5Si + 0.5Al, and A is 2F. Regarding the interlayer cation, the difference between the inner (mean 2.970 Å) and outer (mean 3.237 Å) <I–O> distances is similar to that in the luanshiweiite-2M₁ structure (2.938 and 3.251 Å, respectively). The mean <M1–O> distance in fluorluanshiweiite is 2.108 Å, including the Li–O distance, 2.112 Å, and the Li-F distance, 2.101 Å. These distances are comparable to the sum of the ionic radii of Li⁺, O²⁻ and F⁻ (0.76, 1.40 and 1.38 Å, respectively) [24] and are slightly shorter than the luanshiweiite Li–O distance, 2.140 Å. The <M2–O> distance (mean 1.973 Å) is similar to that of luanshiweiite (mean 1.957 Å) and longer than the values given by Shannon and Prewitt [25] for Al–O (1.91 Å). The octahedral distance from the center of a vacant site to the nearest six oxygen atoms should be considered in reference to other mica minerals, e.g., montdorite and yangzhumingite [26,27,28,29]. In this case, the occurrence of 0.5 vacancies at the M2 site in fluorluanshiweiite must be considered. On the basis of the mean □−O distance in reported dioctahedral micas of 2.174 Å [30,31], the ideal <M2−O> distance in fluorluanshiweiite should be 1.976 Å, which is similar to the distance 1.973 Å observed. The mean <T−O> distance (1.626 Å) in fluorluanshiweiite is similar to that in luanshiweiite (mean 1.628 Å), longer than that in polylithionite (1.621 Å) [32] and shorter than that in trilithionite (1.638 Å) [33,34] due to substitution of smaller Si⁴⁺ and larger Al³⁺ in the tetrahedral layer, which is consistent with the occupancy of Si and Al at the T site in the lepidolite species above. Octahedral vacancies can be introduced by a substitution mechanism such as Li⁺ + 0.5Si⁴⁺ ↔ Al³⁺ + 0.5□.

Bond-valence analysis (BVS): The bond valence (vu) was calculated from the interatomic distance following the procedure of Brown and Altermatt [35]. The bond-valence sums for the I(K), M1(Li), M2(Al_1.5□_0.5), and T(Si_3.5Al_0.5) positions are 0.95, 0.97, 2.31, and 3.97 valence units (vu), respectively, which is in agreement with the expected values given that various cations are present at the same sites. The low BVS for M2 suggests that it has a vacant cation position. The bond-valence sums for the O1, O2, and O3 positions are 2.11, 2.12, and 2.06 vu, respectively. The bond-valence sum for the A site, which is occupied by a hydroxyl group in luanshiweiite [1], is 0.89 vu for F in fluorluanshiweiite. As shown in

Table 7. Bond-valence (vu) analysis for fluorluanshiweiite.

	I-site	M1-site	M2-site	T-site	Sum
O1	0.105 × 2↓			0.980 × 2→	2.11
	0.046 × 2↓
O2	0.107 × 4↓			0.980	2.12
	0.054 × 4↓			0.977
O3		0.175 × 4↓	0.440 × 2↓	1.037	2.06
			0.412 × 2↓
F1		0.135 × 2↓→	0.308 × 2↓→		0.89
Sum	0.95	0.97	2.31	3.97

Notes: Bond valence sums were calculated with the site-occupancy factors given in Table 4. Calculations were done using the equation and constants of [36], S = exp[(R₀–d₀)/b]. The symbols → and ↓ mean that the value must be multiplied by a factor 2 or 4 horizontally and vertically, respectively.

, all the resulting BVS values are comparable to ideal values, and the model basically matches the charge balance requirement.

In conclusion, fluorluanshiweiite is the third light mica with substantial lithium and a stoichiometry intermediate between diocatahedral and trioctahedral; only two other Li micas have this stoichiometry: luanshiweiite [1] and voloshinite [2]. Fluorluanshiweiite can be considered as the F-dominant analogue at the A site of luanshiweiite or a K-dominant analogue at the I site of voloshinite (

Table 8. Comparative characteristics of fluorluanshiweiite and other minerals of the lepidolite species having a similar structure.

	Fluorluanshiweiite			Luanshiweiite *			Voloshinite †
I-site	K			K			Rb
M-site	LiAl1.5□0.5			LiAl1.5□0.5			LiAl1.5□0.5
T-site	Si3.5Al0.5			Si3.5Al0.5			Si3.5Al0.5
A-site	F2			(OH)2			F2
Crystal system	Monoclinic			Monoclinic			Monoclinic
Space group	C/2m			C2/c			C2/c
Polytype	1M			2M1			2M1
a(Å)	5.2030(5)			5.1861(7)			5.191
b(Å)	8.9894(6)			8.9857 (13)			9.025
c(Å)	10.1253(9)			19.970(3)			20.40
β(°)	100.68(1)			95.420(3)			95.37
V(Å3)	465.37(7)			926.5(2)			951.5
Z	2			4			4
Density(cal.)	2.898			2.868			2.95
Optical properties	biaxial (–)			biaxial (–)			biaxial (–)
α	1.554			1.5474			1.511
β	1.581			1.5700			1.586
γ	1.583			1.5729			1.590
2V(cal.)	30°			39°			25°
Selected strongest lines in the powder pattern, The intensities of 8 strongest lines are in bold.	dmeas	Imeas	hkl	dmeas	Imeas	hkl	dmeas	Imeas	hkl
	8.427	25	001	9.891	35	002	10.100	60	002
	4.519	57	020	4.451	31	111	4.550	80	020
	3.856	14	111	3.870	11	113	3.980	40	112
	3.628	61	112	3.703	12	023	3.770	40	023
	3.350	60	022	3.314	36	006	3.350	60	006
	3.091	46	112	3.090	40	115	3.220	40	114
	2.898	25	113	2.973	34	025	3.020	45	025
	2.680	17	023	2.769	24	116	2.805	30	116
	2.586	100	130	2.565	100	116	2.575	100	116
	2.457	25	131	2.454	12	133	2.469	15	133
	2.390	25	132	2.378	31	133	2.410	20	133
	2.254	17	221	2.243	11	221	2.234	10	222
	2.141	14	133	2.130	27	043	2.141	40	135
	1.996	10	223	1.986	30	00,10	1.986	10	224
	1.640	16	116	1.647	32	314	1.660	30	314
	1.506	45	312	1.500	26	060	1.501	40	332
	1.343	10	316	1.345	14	13,13	1.351	10	13,13

Notes: Data reference from * Reference [1], † Reference [2].

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