Kôzulite, an Mn-rich alkali amphibole

The crystal structure of kôzulite, an Mn-rich alkali amphibole with the ideal formula NaNa₂[Mn₄²⁺(Fe³⁺,Al)]Si₈O₂₂(OH)₂, tris­odium tetra­manganese iron/aluminium octa­silicate dihydroxide, was refined from a natural specimen with composition (K_0.20Na_0.80)(Na_1.60Ca_0.18Mn²⁺_0.22)(Mn²⁺_2.14Mn³⁺_0.25Mg_2.20Fe³⁺_0.27Al_0.14)(Si_7.92Al_0.06Ti_0.02)O₂₂[(OH)_1.86F_0.14]. The site occupancies determined from the refinements are M1 = 0.453 (1) Mn + 0.547 (1) Mg, M2 = 0.766 (1) Mn + 0.234 (1) Mg, and M3 = 0.257 (1) Mn + 0.743 (1) Mg, where Mn and Mg represent (Mn+Fe) and (Mg+Al), respectively. The average M—O bond lengths are 2.064 (1), 2.139 (1), and 2.060 (1) Å for the M1, M2, and M3 sites, respectively, indicating the preference of large Mn²⁺ for the M2 site. Four partially occupied amphibole A sites were revealed from the refinement, with A(m) = 0.101 (4) K, A(m)′ = 0.187 (14) Na, A(2) = 0.073 (6) Na, and A(1) = 0.056 (18) Na, in accord with the result derived from microprobe analysis (0.20 K + 0.80 Na), considering experimental uncertainties.

Related literature

For more information on the geologic occurrence of kôzulite, see: Ashley (1986); Banno (1997); Hirtopanu (2006); Kawachi & Coombs (1993); Matsubara et al. (2002); Nambu et al. (1969, 1970, 1981); Watanabe et al. (1976). For the initial structural refinement of kôzulite, see: Fleischer & Nickel (1970); Kitamura & Morimoto (1972). For general background to the amphibole group, see: Hawthorne (1983); Hawthorne et al. (1995, 1996); Hawthorne & Harlow (2008). For background information on the amphibole group and nomenclature, see: Leake (1978); Leake et al. (1997, 2003); Mogessie et al. (2004).

Experimental

Crystal data

• Na₃[Mn₄(FeAl)]Si₈O₂₂(OH)₂

• M_r = 897.29

• Monoclinic, C 2/m

• a = 9.9024 (7) Å

• b = 18.1117 (12) Å

• c = 5.2992 (4) Å

• β = 104.034 (4)°

• V = 922.04 (11) ų

• Z = 2

• Mo Kα radiation

• μ = 2.87 mm⁻¹

• T = 293 K

• 0.06 × 0.05 × 0.04 mm

Data collection

• Bruker APEXII CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Sheldrick, 2008a) T_min = 0.847, T_max = 0.894

• 7829 measured reflections

• 1977 independent reflections

• 1656 reflections with I > 2σ(I)

• R_int = 0.019

Refinement

• R[F² > 2σ(F²)] = 0.023

• wR(F²) = 0.067

• S = 1.08

• 1977 reflections

• 111 parameters

• 1 restraint

• H-atom parameters not refined

• Δρ_max = 0.58 e Å⁻³

• Δρ_min = −0.59 e Å⁻³

Data collection: APEX2 (Bruker, 2003); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008b); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008b); molecular graphics: XtalDraw (Downs & Hall-Wallace, 2003); software used to prepare material for publication: SHELXTL (Sheldrick, 2008b).

Supporting information

S1. Comment

Kôzulite, with the ideal formula NaNa₂[Mn₄²⁺(Fe³⁺,Al)]Si₈O₂₂(OH)₂, is an Mn-rich alkali member of the rock-forming amphibole family and was first described by Nambu et al. (1969). Kitamura and Morimoto (1972), in a meeting abstract, presented the structure refinement of a kôzulite crystal with the composition (Na_2.54K_0.27Ca_0.19)(Mn_3.69Mg_0.63Fe³⁺_0.33Al³⁺_0.31)Σi_8.00O_21.78[(OH)_2.18F_0.04]. However, they did not report its detailed structure information, such as atomic coordinates and displacement parameters. This study presents the first reported structure of kôzulite based on single-crystal X-ray diffraction data, as a part of our effort to build an integrated, web-based database of Raman spectra, X-ray diffraction, and chemistry data for all minerals (http://rruff.info).

The site occupancies determined from the refinements are M1 = 0.453 (1) Mn + 0.547 (1) Mg, M2 = 0.766 (1) Mn + 0.234 (1) Mg, and M3 = 0.257 (1) Mn + 0.743 (1) Mg, where Mn and Mg represent (Mn +Fe) and (Mg + Al), respectively. There results should be compared to those given by Kitamura and Morimoto (1972) for their kôzulite crystal: M1 = 0.78 Mn + 0.22 Mg, M2 = 0.95 Mn + 0.05 Mg, and M3 = 0.58 Mn + 0.42 Mg. The average M—O bond lengths are 2.064 (1), 2.139 (1), and 2.060 (1) Å for the M1, M2, and M3 sites, respectively. These values indicate that the M2 site is dominantly occupied by larger Mn²⁺, whereas the M1 and M3 sites should have similar amounts of (Mn³⁺ + Fe³⁺) and Mg. The relatively short average M3—O distance (versus. M1—O) suggests that Al³⁺ is preferentially ordered into the M3 site. Our results on kôzulite are very similar to those observed by Hawthorne et al. (1995) for ungarettiite with the composition (K_0.15Na_0.82)(Na_1.97Ca_0.03)˘Mn²⁺_1.66Mn³⁺_2.97Mg_0.34Fe³⁺_0.03Zn_0.01)(Si_7.99Al_0.01)O₂₂O_2. The average M—O distances in ungarettiite are 2.03, 2.17, and 2.01 Å for the M1, M2, and M3 sites, respectively, pointing to the strong ordering of larger Mn²⁺ into the M2 site and smaller Mn³⁺ into M1 and M3.

Four partially occupied amphibole A sites [A(m), A(m)', A(2), and A(1)] were revealed from the structure refinements. The refinement shows that K prefers the A(m) site, whereas Na is distributed among the other three sites. The refined A site occupancies are 0.208 K + 0.764Na [A(m) = 0.208 (4) K, A(m)' = 0.374 (14) Na, A(2) = 0.146 (6)Na, and A(1) = 0.224 (18) Na], consistent with the result derived from microprobe analysis (0.20 K + 0.80Na), considering experimental uncertainties. The presence of two distinct A sites on the mirror plane, A(m) and A(m)' has also been observed in many other alkali amphiboles (e.g., Hawthorne et al. 1996; Hawthorne and Harlow 2008).

Related literature

For more information on the geologic occurrence of kôzulite, see: Ashley (1986); Banno (1997); Hirtopanu (2006); Kawachi & Coombs (1993); Matsubara et al. (2002); Nambu et al. (1969, 1970, 1981); Watanabe et al. (1976). For the initial structural refinement of kôzulite, see: Fleischer & Nickel (1970); Kitamura & Morimoto (1972). For general background to the amphibole group, see: Hawthorne (1983); Hawthorne et al. (1995, 1996); Hawthorne & Harlow (2008).For background information on the amphibole group and nomenclature, see: Leake (1978); Leake et al. (1997, 2003); Mogessie et al. (2004).

S2. Experimental

The kôzulite specimen used in this study is from the type locality Tanohata Mine, Iwate Prefecture, Tohoku Region, Honshu Island, Japan and is in the collection of the RRUFF project (deposition No. R070122; http://rruff.info). The crystal chemistry was determined with a CAMECA SX50 electron microprobe (http://rruff.info) on the same single-crystal used for the collection of X-ray intensity data. The average composition (10 point analyses) yielded a chemical formula (normalized on the basis of 23 oxygen): (K_0.20Na_0.80)(Na_1.60Ca_0.18Mn²⁺_0.22)˘Mn²⁺_2.14Mn³⁺_0.25Mg_2.20Fe³⁺_0.27Al_0.14)˘Si_7.92Al_0.06Ti_0.02)O₂₂[(OH)_1.86F_0.14].

S3. Refinement

The chemical analysis and crystal-chemical considerations show that the C-group cations consist of Mn²⁺, Mn³⁺, Fe³⁺, Mg, and Al³⁺. Because of similar X-ray scattering powers, Fe and Mn were grouped together (represented by the scattering factor for Mn) and Mg and Al together (represented by Mg) throughout the structure refinements. No refinement was made for the cations in the M4 site (= Na_0.80Ca_0.09Mn²⁺_0.11); they were assigned based on crystal-chemical considerations and previous studies on amphiboles (Hawthorne 1983). The total Mn and Mg in the M1 + M2 + M3 sites were fixed to those from the chemical analysis. To dampen the extreme correlations that would otherwise occur among the refined A-site variables, the isotropic displacement factors of these A sites were constrained to be equal (Hawthorne & Harlow 2008).

Computing details

Data collection: APEX2 (Bruker, 2003); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008b); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008b); molecular graphics: XtalDraw (Downs & Hall-Wallace, 2003); software used to prepare material for publication: SHELXTL (Sheldrick, 2008b).

Figures

Fig. 1. The crystal structure of kôzulite. Green and yellow tetrahedra represent [Si1O4] and [Si2O4] groups, respectively. Purple, blue, and red octahedra represent the M1, M2, and M3 octahedra, respectively. The small blue and large pink spheres represent the M4 and A cations, respectively.

trisodium tetramanganese iron/aluminium octasilicate dihydroxide

Crystal data

Na3[Mn4(Fe)]Si8O22(OH)2	F(000) = 954
Mr = 897.29	Dx = 3.232 Mg m^−3
Monoclinic, C2/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2y	Cell parameters from 2537 reflections
a = 9.9024 (7) Å	θ = 4.0–34.7°
b = 18.1117 (12) Å	µ = 2.87 mm^−1
c = 5.2992 (4) Å	T = 293 K
β = 104.034 (4)°	Euhedral, brown
V = 922.04 (11) Å^3	0.06 × 0.05 × 0.04 mm
Z = 2

Data collection

Bruker APEXII CCD area-detector diffractometer	1977 independent reflections
Radiation source: fine-focus sealed tube	1656 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.019
φ and ω scans	θmax = 34.4°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 2008a)	h = −15→15
Tmin = 0.847, Tmax = 0.894	k = −28→28
7829 measured reflections	l = −8→7

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.023	H-atom parameters not refined
wR(F^2) = 0.067	w = 1/[σ^2(Fo^2) + (0.0302P)^2 + 1.2008P] where P = (Fo^2 + 2Fc^2)/3
S = 1.08	(Δ/σ)max < 0.001
1977 reflections	Δρmax = 0.58 e Å^−3
111 parameters	Δρmin = −0.59 e Å^−3
1 restraint

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
M1	0.0000	0.08447 (2)	0.5000	0.00933 (11)	0.4529 (19)
M1A	0.0000	0.08447 (2)	0.5000	0.00933 (11)	0.5471 (19)
M2	0.0000	0.182241 (18)	0.0000	0.00935 (9)	0.766 (2)
M2A	0.0000	0.182241 (18)	0.0000	0.00935 (9)	0.234 (2)
M3	0.0000	0.0000	0.0000	0.00682 (19)	0.256 (4)
M3A	0.0000	0.0000	0.0000	0.00682 (19)	0.744 (4)
M4A	0.0000	0.27152 (4)	0.5000	0.02191 (15)	0.79
M4B	0.0000	0.27152 (4)	0.5000	0.02191 (15)	0.09
M4C	0.0000	0.27152 (4)	0.5000	0.02191 (15)	0.11
Si1	0.28233 (4)	0.084285 (19)	0.28706 (7)	0.00858 (8)
Si2	0.28734 (4)	0.16909 (2)	0.79054 (7)	0.00908 (8)
O1	0.11555 (10)	0.08452 (5)	0.2127 (2)	0.01077 (18)
O2	0.11918 (11)	0.16575 (6)	0.7170 (2)	0.01460 (19)
O3	0.10330 (15)	0.0000	0.7118 (3)	0.0131 (3)
O4	0.35819 (12)	0.24732 (6)	0.7901 (2)	0.0179 (2)
O5	0.34710 (10)	0.12714 (6)	0.0742 (2)	0.01335 (19)
O6	0.34473 (10)	0.11704 (6)	0.57692 (19)	0.01358 (19)
O7	0.34279 (16)	0.0000	0.2884 (3)	0.0154 (3)
AM	0.5211 (9)	0.0000	0.053 (2)	0.0149 (9)*	0.104 (4)
AM'	0.5562 (10)	0.0000	0.1298 (17)	0.0149 (9)*	0.187 (11)
A2	0.5000	−0.0215 (15)	0.0000	0.0149 (9)*	0.073 (6)
A1	0.5386 (18)	−0.0192 (18)	0.103 (4)	0.0149 (9)*	0.056 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
M1	0.00812 (19)	0.01278 (19)	0.00693 (19)	0.000	0.00151 (14)	0.000
M1A	0.00812 (19)	0.01278 (19)	0.00693 (19)	0.000	0.00151 (14)	0.000
M2	0.00981 (15)	0.00801 (14)	0.01081 (16)	0.000	0.00360 (11)	0.000
M2A	0.00981 (15)	0.00801 (14)	0.01081 (16)	0.000	0.00360 (11)	0.000
M3	0.0078 (3)	0.0059 (3)	0.0063 (3)	0.000	0.0009 (2)	0.000
M3A	0.0078 (3)	0.0059 (3)	0.0063 (3)	0.000	0.0009 (2)	0.000
M4A	0.0226 (4)	0.0251 (4)	0.0224 (4)	0.000	0.0139 (3)	0.000
M4B	0.0226 (4)	0.0251 (4)	0.0224 (4)	0.000	0.0139 (3)	0.000
M4C	0.0226 (4)	0.0251 (4)	0.0224 (4)	0.000	0.0139 (3)	0.000
Si1	0.00867 (16)	0.00776 (15)	0.00854 (16)	−0.00068 (11)	0.00063 (12)	0.00007 (11)
Si2	0.00895 (16)	0.00906 (15)	0.00918 (16)	−0.00125 (11)	0.00213 (12)	0.00087 (11)
O1	0.0088 (4)	0.0112 (4)	0.0115 (4)	−0.0013 (3)	0.0009 (3)	−0.0005 (3)
O2	0.0093 (4)	0.0202 (5)	0.0138 (5)	0.0015 (4)	0.0018 (3)	0.0031 (4)
O3	0.0139 (6)	0.0114 (6)	0.0133 (6)	0.000	0.0021 (5)	0.000
O4	0.0236 (5)	0.0115 (4)	0.0186 (5)	−0.0056 (4)	0.0054 (4)	0.0012 (4)
O5	0.0112 (4)	0.0171 (5)	0.0114 (4)	0.0000 (3)	0.0021 (3)	0.0049 (3)
O6	0.0115 (4)	0.0184 (5)	0.0099 (4)	0.0004 (3)	0.0006 (3)	−0.0039 (3)
O7	0.0149 (7)	0.0076 (5)	0.0227 (7)	0.000	0.0022 (5)	0.000

Geometric parameters (Å, º)

M1—O3^i	2.0223 (10)	M4A—O5^ix	3.0160 (12)
M1—O3	2.0223 (10)	Si1—O1	1.6022 (11)
M1—O2	2.0551 (11)	Si1—O6	1.6226 (11)
M1—O2^ii	2.0551 (11)	Si1—O5	1.6240 (10)
M1—O1	2.1148 (10)	Si1—O7	1.6391 (7)
M1—O1^ii	2.1148 (10)	Si2—O4	1.5814 (11)
M2—O4^iii	2.0197 (11)	Si2—O2	1.6166 (11)
M2—O4^iv	2.0197 (11)	Si2—O5^x	1.6598 (11)
M2—O2^v	2.1425 (11)	Si2—O6	1.6748 (11)
M2—O2^ii	2.1425 (11)	AM—O7^xi	2.506 (7)
M2—O1^vi	2.2554 (10)	AM—O5^xii	2.809 (3)
M2—O1	2.2554 (10)	AM—O5^xi	2.809 (3)
M3—O3^i	2.0339 (15)	AM—O5^viii	2.894 (4)
M3—O3^v	2.0339 (15)	AM'—O7^xi	2.643 (7)
M3—O1	2.0730 (10)	AM'—O6^xiii	2.671 (6)
M3—O1^vi	2.0730 (10)	AM'—O6^xiv	2.671 (6)
M3—O1^vii	2.0730 (10)	AM'—O5^xii	2.809 (4)
M3—O1^viii	2.0730 (10)	A2—O7^xi	2.463 (4)
M4A—O4^ix	2.3450 (12)	A2—O5^viii	2.53 (2)
M4A—O4^iii	2.3450 (12)	A2—O5^xi	2.53 (2)
M4A—O2^ii	2.3930 (13)	A1—O6^xiv	2.53 (3)
M4A—O2	2.3930 (13)	A1—O5^xi	2.55 (3)
M4A—O6^iii	2.6283 (12)	A1—O7^xi	2.644 (17)
M4A—O6^ix	2.6283 (12)	A1—O5^viii	2.70 (3)
M4A—O5^iii	3.0160 (12)
O3^i—M1—O3	81.68 (6)	O1^vi—M2—O1	76.60 (5)
O3^i—M1—O2	175.50 (5)	O3^i—M3—O3^v	180.00 (6)
O3—M1—O2	94.98 (4)	O3^i—M3—O1	84.47 (4)
O3^i—M1—O2^ii	94.98 (4)	O3^v—M3—O1	95.53 (4)
O3—M1—O2^ii	175.50 (5)	O3^i—M3—O1^vi	95.53 (4)
O2—M1—O2^ii	88.50 (6)	O3^v—M3—O1^vi	84.47 (4)
O3^i—M1—O1	83.68 (5)	O1—M3—O1^vi	84.81 (5)
O3—M1—O1	96.35 (5)	O3^i—M3—O1^vii	95.53 (4)
O2—M1—O1	93.72 (4)	O3^v—M3—O1^vii	84.47 (4)
O2^ii—M1—O1	86.24 (4)	O1—M3—O1^vii	180.00 (6)
O3^i—M1—O1^ii	96.35 (5)	O1^vi—M3—O1^vii	95.19 (5)
O3—M1—O1^ii	83.68 (5)	O3^i—M3—O1^viii	84.47 (4)
O2—M1—O1^ii	86.24 (4)	O3^v—M3—O1^viii	95.53 (4)
O2^ii—M1—O1^ii	93.72 (4)	O1—M3—O1^viii	95.19 (5)
O1—M1—O1^ii	179.95 (6)	O1^vi—M3—O1^viii	180.00 (3)
O4^iii—M2—O4^iv	101.65 (7)	O1^vii—M3—O1^viii	84.81 (5)
O4^iii—M2—O2^v	92.64 (4)	O1—Si1—O6	111.41 (5)
O4^iv—M2—O2^v	97.47 (4)	O1—Si1—O5	112.64 (5)
O4^iii—M2—O2^ii	97.47 (4)	O6—Si1—O5	111.04 (6)
O4^iv—M2—O2^ii	92.64 (4)	O1—Si1—O7	110.92 (6)
O2^v—M2—O2^ii	163.97 (6)	O6—Si1—O7	106.35 (7)
O4^iii—M2—O1^vi	166.32 (4)	O5—Si1—O7	104.05 (7)
O4^iv—M2—O1^vi	91.14 (4)	O4—Si2—O2	117.68 (6)
O2^v—M2—O1^vi	80.77 (4)	O4—Si2—O5^x	110.52 (6)
O2^ii—M2—O1^vi	86.65 (4)	O2—Si2—O5^x	108.75 (6)
O4^iii—M2—O1	91.14 (4)	O4—Si2—O6	106.26 (6)
O4^iv—M2—O1	166.32 (4)	O2—Si2—O6	108.33 (6)
O2^v—M2—O1	86.65 (4)	O5^x—Si2—O6	104.45 (6)
O2^ii—M2—O1	80.77 (4)

Symmetry codes: (i) −x, −y, −z+1; (ii) −x, y, −z+1; (iii) −x+1/2, −y+1/2, −z+1; (iv) x−1/2, −y+1/2, z−1; (v) x, y, z−1; (vi) −x, y, −z; (vii) −x, −y, −z; (viii) x, −y, z; (ix) x−1/2, −y+1/2, z; (x) x, y, z+1; (xi) −x+1, −y, −z; (xii) −x+1, y, −z; (xiii) −x+1, y, −z+1; (xiv) −x+1, −y, −z+1.