Penikisite, BaMg2Al2(PO4)3(OH)3, isostructural with bjarebyite

Bowman, M.G.; Downs, R.T.; Yang, H.

doi:10.1107/S1600536812051793

inorganic compounds

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ISSN: 2056-9890

Volume 69| Part 2| February 2013| Pages i4-i5

doi:10.1107/S1600536812051793

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Penikisite, BaMg₂Al₂(PO₄)₃(OH)₃, isostructural with bjarebyite

Michael G. Bowman,^a ^* Robert T. Downs ^a and Hexiong Yang ^a

^aDepartment of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721-0077, USA
^*Correspondence e-mail: bowman90@email.arizona.edu

(Received 6 December 2012; accepted 23 December 2012; online 9 January 2013)

The bjarebyite group of minerals, characterized by the general formula BaX₂Y₂(PO₄)₃(OH)₃, with X = Mg, Fe²⁺ or Mn²⁺, and Y = Al or Fe³⁺, includes five members: bjarebyite BaMn²⁺₂Al₂(PO₄)₃(OH)₃, johntomaite BaFe²⁺₂Fe³⁺₂(PO₄)₃(OH)₃, kulanite BaFe²⁺₂Al₂(PO₄)₃(OH)₃, penikisite BaMg₂Al₂(PO₄)₃(OH)₃, and perloffite BaMn²⁺₂Fe³⁺₂(PO₄)₃(OH)₃. Thus far, the crystal structures of all minerals in the group, but penikisite, have been determined. The present study reports the first structure determination of penikisite (barium dimagnesium dialuminium triphosphate trihydroxide) using single-crystal X-ray diffraction data of a crystal from the type locality, Mayo Mining District, Yukon Territory, Canada. Penikisite is isotypic with other members of the bjarebyite group with space group P2₁/m, rather than triclinic (P1 or P-1), as previously suggested. Its structure consists of edge-shared [AlO₃(OH)₃] octahedral dimers linking via corners to form chains along [010]. These chains are decorated with PO₄ tetrahedra (one of which has site symmetry m) and connected along [100] via edge-shared [MgO₅(OH)] octahedral dimers and eleven-coordinated Ba²⁺ ions (site symmetry m), forming a complex three-dimensional network. O—H⋯O hydrogen bonding provides additional linkage between chains. Microprobe analysis of the crystal used for data collection indicated that Mn substitutes for Mg at the 1.5% (apfu) level.

Related literature

For penikisite, see: Mandarino et al. (1977 ). For other mineral members in the bjarebyite group, see: Moore & Araki (1974 ); Cooper & Hawthorne (1994 ); Kolitsch et al. (2000 ); Elliott & Willis (2011 ). For the definition of polyhedral distortion, see: Robinson et al. (1971 ).

Experimental

Crystal data

BaMg₂Al₂(PO₄)₃(OH)₃
M_r = 576.77
Monoclinic, P 2₁ /m
a = 8.9577 (4) Å
b = 12.0150 (5) Å
c = 4.9079 (2) Å
β = 100.505 (2)°
V = 519.37 (4) Å³
Z = 2
Mo Kα radiation
μ = 4.72 mm⁻¹
T = 293 K
0.09 × 0.09 × 0.08 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2005 ) T_min = 0.676, T_max = 0.704
7681 measured reflections
1970 independent reflections
1925 reflections with I > 2σ(I)
R_int = 0.020

Refinement

R[F² > 2σ(F²)] = 0.015
wR(F²) = 0.039
S = 1.14
1970 reflections
119 parameters
1 restraint
All H-atom parameters refined
Δρ_max = 0.72 e Å⁻³
Δρ_min = −0.80 e Å⁻³

Table 1
Selected bond lengths (Å)

Mg—O7ⁱ	2.0591 (11)
Mg—O1ⁱⁱ	2.0864 (10)
Mg—O2ⁱⁱⁱ	2.1227 (10)
Mg—OH9^iv	2.1729 (11)
Mg—O5^v	2.2090 (12)
Al—O3^vi	1.8523 (11)
Al—O6	1.9080 (11)
Al—O5^vii	1.9287 (10)
Al—OH9	1.9397 (11)
Al—OH9^viii	1.9440 (11)
Al—OH8	1.9477 (7)
P1—O2	1.5232 (14)
P1—O1	1.5278 (15)
P1—O3	1.5321 (10)
P1—O3^ix	1.5321 (10)
P2—O4	1.5083 (11)
P2—O7	1.5272 (11)
P2—O6	1.5443 (11)
P2—O5	1.5680 (10)
Symmetry codes: (i) $[-x+1, y-{\script{1\over 2}}, -z+1]$ ; (ii) x, y-1, z-1; (iii) x, y-1, z; (iv) $[x, -y+{\script{1\over 2}}, z]$ ; (v) $[x, -y+{\script{1\over 2}}, z-1]$ ; (vi) -x, -y+1, -z+1; (vii) x, y, z-1; (viii) -x, -y+1, -z; (ix) $[x, -y+{\script{3\over 2}}, z]$ .

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
OH8—H1⋯O6^vii	0.79 (4)	2.66 (3)	3.3180 (16)	142 (1)
OH9—H2⋯O3	0.78 (3)	1.89 (3)	2.6512 (13)	166 (3)
Symmetry code: (vii) x, y, z-1.

Data collection: APEX2 (Bruker, 2004 ); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XtalDraw (Downs & Hall-Wallace, 2003 ); software used to prepare material for publication: publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: 10.1107/S1600536812051793/hb7009sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536812051793/hb7009Isup2.hkl

checkCIF report

Comment top

The bjarebyite group of minerals is characterized by the general chemical formula BaX₂Y₂(PO₄)₃(OH)₃, where X=Mn²⁺, Fe²⁺ or Mg and Y=Al or Fe³⁺, and includes five members: bjarebyite BaMn²⁺₂Al₂(PO₄)₃(OH)₃, johntomaite BaFe²⁺₂Fe³⁺₂(PO₄)₃(OH)₃, kulanite BaFe²⁺₂Al₂(PO₄)₃(OH)₃, penikisite BaMg₂Al₂(PO₄)₃(OH)₃, and perloffite BaMn²⁺₂Fe³⁺₂(PO₄)₃(OH)₃. Except for penikisite, the crystal structures of all other minerals in the group have been determined (Moore and Araki, 1974; Cooper and Hawthorne, 1994; Kolitsch et al., 2000; Elliot & Willis, 2011), which all possess space group P2₁/m. Penikisite was first described by Mandarino et al. (1977) as triclinic with space group P1 or P1 (albeit strongly pseudomonoclinic), based on the observation of asymmetric optical dispersion. Since then, no detailed crystallographic study on penikisite has been reported. In our efforts to understand the hydrogen bonding environments in minerals, we conducted a structure determination of penikisite from the type locality by means of single-crystal X-ray diffraction.

Penikisite is isotypic with other members of the bjarebyite group, with space group P2₁/m. Its structure consists of edge-shared [AlO₃(OH)₃] octahedral dimers connected via corners to form chains along [010]. These chains are decorated with PO₄ tetrahedra and linked along [100] via edge-shared MgO₅(OH) octahedral dimers and eleven-coordinated Ba atoms to form a complex three-dimensional network (Figs. 1 and 2). The hydrogen bonding provides additional linkage between chains.

Similar to other minerals in the bjarebyite group, the YO₅(OH) octahedra in penikisite are noticeably distorted, as measured by the octahedral angle variance (OAV) and quadratic elongation (OQE) (Robinson et al., 1971), which are 188 and 1.057, respectively. In contrast, the OAV and OQE values are 32 and 1.010 for the XO₃(OH)₃ octahedra in penikisite. From penikisite to the Fe-analogue kulanite (Cooper and Hawthorne, 1994), and to the Mn-analogue bjarebyite (Moore and Araki, 1974), the average X-O distance increases from 2.117 to 2.146, and to 2.162 Å, respectively, in accordance with the increase in the ionic radius in this site.

There are two hydrogen bonds in penikisite, one between OH8 and O6 [3.318 (2) Å] and the other between OH9 and O3 [2.651 (1) Å], agreeing well with the results obtained by Elliott & Willis (2011) from perloffite. However, Cooper and Hawthorne (1994) proposed a disorder model for H1 in kulanite. The H atoms were not located in the structure of bjarebyite (Moore and Araki, 1974) or johntomaite (Kolitsch et al., 2000).

Related literature top

For penikisite, see: Mandarino et al. (1977). For other mineral members in the bjarebyite group, see: Moore & Araki (1974); Cooper & Hawthorne (1994); Kolitsch et al. (2000); Elliott & Willis (2011). For the definition of polyhedral distortion, see: Robinson et al. (1971).

Experimental top

The penikisite crystal used in this study is from the type locality, 16 miles north of the Hess River, Mayo Mining District, Yukon Territory, Canada and is in the collection of the RRUFF project (http://rruff.info/R060160), donated by Mark Mauthner. Its chemistry was determined with a CAMECA SX50 electron microprobe (8 analysis points), yielding the empirical chemical formula, calculated on the basis of 13.5 O atoms, Ba_1.00(Mg_1.97Mn_0.03)_Σ₌₂Al_2.00(P_1.00O₄)₃(OH)₃ (OH was estimated by charge balance and difference).

Computing details top

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XtalDraw (Downs & Hall-Wallace, 2003); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

	Fig. 1. Crystal structure of penikisite in polyhedral representation. Large and small spheres represent Ba and H atoms, respectively.
	Fig. 2. The crystal structure of penikisite, showing atoms, except for H, with displacement ellipsoids at the 99% probability level. Gray, pink, green, yellow, and red ellipsoids represent Ba, Mg, Al, P, and O atoms, respectively. H atoms are given as turquoise spheres with an arbitrary radius.

Barium dimagnesium dialuminium triphosphate trihydroxide top

Crystal data top

Al₄H₆Mg_3.94Mn_0.06O₃₀P₆·2(Ba)	F(000) = 549
M_r = 576.77	nearly cube
Monoclinic, P12₁/m1	D_x = 3.688 Mg m⁻³
Hall symbol: -P 2yb	Mo Kα radiation, λ = 0.71073 Å
a = 8.9577 (4) Å	Cell parameters from 6030 reflections
b = 12.0150 (5) Å	θ = 2.9–32.6°
c = 4.9079 (2) Å	µ = 4.72 mm⁻¹
β = 100.505 (2)°	T = 293 K
V = 519.37 (4) Å³	Cube, green
Z = 2	0.09 × 0.09 × 0.08 mm

Data collection top

Bruker APEXII CCD diffractometer	1970 independent reflections
Radiation source: fine-focus sealed tube	1925 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.020
ϕ and ω scan	θ_max = 32.6°, θ_min = 2.9°
Absorption correction: multi-scan (SADABS; Sheldrick 2005)	h = −13→12
T_min = 0.676, T_max = 0.704	k = −15→18
7681 measured reflections	l = −7→7

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F² > 2σ(F²)] = 0.015	All H-atom parameters refined
wR(F²) = 0.039	w = 1/[σ²(F_o²) + (0.020P)² + 0.2753P] where P = (F_o² + 2F_c²)/3
S = 1.14	(Δ/σ)_max = 0.001
1970 reflections	Δρ_max = 0.72 e Å⁻³
119 parameters	Δρ_min = −0.80 e Å⁻³
1 restraint	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0021 (5)

Crystal data top

Al₄H₆Mg_3.94Mn_0.06O₃₀P₆·2(Ba)	V = 519.37 (4) Å³
M_r = 576.77	Z = 2
Monoclinic, P12₁/m1	Mo Kα radiation
a = 8.9577 (4) Å	µ = 4.72 mm⁻¹
b = 12.0150 (5) Å	T = 293 K
c = 4.9079 (2) Å	0.09 × 0.09 × 0.08 mm
β = 100.505 (2)°

Data collection top

Bruker APEXII CCD diffractometer	1970 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick 2005)	1925 reflections with I > 2σ(I)
T_min = 0.676, T_max = 0.704	R_int = 0.020
7681 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.015	1 restraint
wR(F²) = 0.039	All H-atom parameters refined
S = 1.14	Δρ_max = 0.72 e Å⁻³
1970 reflections	Δρ_min = −0.80 e Å⁻³
119 parameters

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Ba	0.547869 (12)	0.7500	0.74171 (2)	0.00734 (5)
Mg	0.29439 (5)	−0.11139 (4)	0.20677 (10)	0.00705 (9)	0.9850 (1)
Mn	0.29439 (5)	−0.11139 (4)	0.20677 (10)	0.00705 (9)	0.0150 (1)
Al	0.09176 (4)	0.40084 (3)	0.12947 (8)	0.00401 (8)
P1	0.15736 (6)	0.7500	0.68481 (10)	0.00467 (9)
P2	0.33413 (4)	0.44282 (3)	0.70566 (7)	0.00495 (7)
O1	0.27909 (16)	0.7500	0.9471 (3)	0.0072 (2)
O2	0.23251 (16)	0.7500	0.4303 (3)	0.0068 (2)
O3	0.05983 (11)	0.64525 (9)	0.6850 (2)	0.00791 (18)
O4	0.36649 (12)	0.55738 (9)	0.6050 (2)	0.00846 (18)
O5	0.25965 (11)	0.45434 (9)	0.9697 (2)	0.00811 (18)
O6	0.22678 (12)	0.38012 (9)	0.4741 (2)	0.00917 (18)
O7	0.47653 (12)	0.37189 (9)	0.7901 (2)	0.00821 (18)
OH8	0.12478 (17)	0.2500	0.0077 (3)	0.0083 (3)
OH9	0.06100 (12)	0.55814 (9)	0.1891 (2)	0.00679 (17)
H1	0.137 (4)	0.2500	−0.147 (8)	0.030*
H2	0.046 (3)	0.585 (2)	0.325 (5)	0.030*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Ba	0.00667 (6)	0.00826 (7)	0.00724 (6)	0.000	0.00171 (4)	0.000
Mg	0.0069 (2)	0.0070 (2)	0.00715 (19)	0.00042 (16)	0.00119 (16)	−0.00064 (16)
Mn	0.0069 (2)	0.0070 (2)	0.00715 (19)	0.00042 (16)	0.00119 (16)	−0.00064 (16)
Al	0.00373 (17)	0.00395 (17)	0.00440 (16)	−0.00027 (13)	0.00091 (13)	0.00002 (13)
P1	0.00489 (19)	0.0050 (2)	0.00428 (18)	0.000	0.00138 (15)	0.000
P2	0.00499 (14)	0.00536 (15)	0.00459 (14)	0.00024 (11)	0.00113 (11)	0.00027 (10)
O1	0.0072 (6)	0.0085 (6)	0.0055 (6)	0.000	0.0001 (5)	0.000
O2	0.0088 (6)	0.0061 (6)	0.0062 (6)	0.000	0.0036 (5)	0.000
O3	0.0082 (4)	0.0069 (4)	0.0095 (4)	−0.0029 (3)	0.0040 (3)	−0.0015 (3)
O4	0.0101 (4)	0.0070 (4)	0.0083 (4)	−0.0001 (3)	0.0018 (3)	0.0023 (3)
O5	0.0084 (4)	0.0102 (5)	0.0067 (4)	−0.0008 (4)	0.0037 (3)	−0.0006 (3)
O6	0.0093 (4)	0.0100 (5)	0.0073 (4)	−0.0002 (4)	−0.0008 (3)	−0.0015 (3)
O7	0.0058 (4)	0.0087 (5)	0.0102 (4)	0.0021 (3)	0.0018 (3)	0.0020 (3)
OH8	0.0110 (6)	0.0071 (6)	0.0071 (6)	0.000	0.0027 (5)	0.000
OH9	0.0078 (4)	0.0076 (4)	0.0049 (4)	−0.0001 (3)	0.0012 (3)	−0.0016 (3)

Geometric parameters (Å, º) top

Ba—O7ⁱ	2.7669 (10)	Mg—O5^x	2.2090 (12)
Ba—O7ⁱⁱ	2.7669 (10)	Al—O3^xi	1.8523 (11)
Ba—O1	2.7744 (14)	Al—O6	1.9080 (11)
Ba—O4	2.8370 (11)	Al—O5^xii	1.9287 (10)
Ba—O4ⁱⁱⁱ	2.8370 (11)	Al—OH9	1.9397 (11)
Ba—O6^iv	2.9019 (11)	Al—OH9^xiii	1.9440 (11)
Ba—O6^v	2.9019 (10)	Al—OH8	1.9477 (7)
Ba—O2	2.9566 (15)	P1—O2	1.5232 (14)
Ba—OH8^v	2.9658 (15)	P1—O1	1.5278 (15)
Ba—O7^v	2.9661 (10)	P1—O3	1.5321 (10)
Ba—O7^iv	2.9661 (10)	P1—O3ⁱⁱⁱ	1.5321 (10)
Mg—O4^vi	2.0490 (11)	P2—O4	1.5083 (11)
Mg—O7^vii	2.0591 (11)	P2—O7	1.5272 (11)
Mg—O1^viii	2.0864 (10)	P2—O6	1.5443 (11)
Mg—O2^ix	2.1227 (10)	P2—O5	1.5680 (10)
Mg—OH9^vi	2.1729 (11)

O4^vi—Mg—O7^vii	83.31 (4)	O3^xi—Al—OH9^xiii	89.97 (5)
O4^vi—Mg—O1^viii	144.07 (5)	O6—Al—OH9^xiii	170.24 (5)
O7^vii—Mg—O1^viii	83.17 (5)	O5^xii—Al—OH9^xiii	94.31 (5)
O4^vi—Mg—O2^ix	79.75 (5)	OH9—Al—OH9^xiii	77.04 (5)
O7^vii—Mg—O2^ix	105.87 (5)	O3^xi—Al—OH8	92.21 (5)
O1^viii—Mg—O2^ix	72.26 (5)	O6—Al—OH8	92.49 (6)
O4^vi—Mg—OH9^vi	94.50 (4)	O5^xii—Al—OH8	90.69 (5)
O7^vii—Mg—OH9^vi	168.32 (5)	OH9—Al—OH8	170.59 (5)
O1^viii—Mg—OH9^vi	104.78 (5)	OH9^xiii—Al—OH8	96.50 (6)
O2^ix—Mg—OH9^vi	84.93 (5)	O2—P1—O1	109.67 (8)
O4^vi—Mg—O5^x	102.80 (5)	O2—P1—O3	109.74 (5)
O7^vii—Mg—O5^x	97.57 (4)	O1—P1—O3	108.60 (5)
O1^viii—Mg—O5^x	111.89 (4)	O2—P1—O3ⁱⁱⁱ	109.74 (5)
O2^ix—Mg—O5^x	156.55 (5)	O1—P1—O3ⁱⁱⁱ	108.60 (5)
OH9^vi—Mg—O5^x	71.65 (4)	O3—P1—O3ⁱⁱⁱ	110.46 (8)
O3^xi—Al—O6	85.88 (5)	O4—P2—O7	113.41 (6)
O3^xi—Al—O5^xii	174.52 (5)	O4—P2—O6	109.59 (6)
O6—Al—O5^xii	89.36 (5)	O7—P2—O6	107.74 (6)
O3^xi—Al—OH9	94.60 (5)	O4—P2—O5	109.04 (6)
O6—Al—OH9	94.47 (5)	O7—P2—O5	106.57 (6)
O5^xii—Al—OH9	83.07 (5)	O6—P2—O5	110.45 (6)

Symmetry codes: (i) −x+1, y+1/2, −z+2; (ii) −x+1, −y+1, −z+2; (iii) x, −y+3/2, z; (iv) −x+1, y+1/2, −z+1; (v) −x+1, −y+1, −z+1; (vi) x, −y+1/2, z; (vii) −x+1, y−1/2, −z+1; (viii) x, y−1, z−1; (ix) x, y−1, z; (x) x, −y+1/2, z−1; (xi) −x, −y+1, −z+1; (xii) x, y, z−1; (xiii) −x, −y+1, −z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
OH8—H1···O6^xii	0.79 (4)	2.66 (3)	3.3180 (16)	142 (1)
OH9—H2···O3	0.78 (3)	1.89 (3)	2.6512 (13)	166 (3)

Symmetry code: (xii) x, y, z−1.

Experimental details

Crystal data
Chemical formula	Al₄H₆Mg_3.94Mn_0.06O₃₀P₆·2(Ba)
M_r	576.77
Crystal system, space group	Monoclinic, P12₁/m1
Temperature (K)	293
a, b, c (Å)	8.9577 (4), 12.0150 (5), 4.9079 (2)
β (°)	100.505 (2)
V (Å³)	519.37 (4)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	4.72
Crystal size (mm)	0.09 × 0.09 × 0.08

Data collection
Diffractometer	Bruker APEXII CCD diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick 2005)
T_min, T_max	0.676, 0.704
No. of measured, independent and observed [I > 2σ(I)] reflections	7681, 1970, 1925
R_int	0.020
(sin θ/λ)_max (Å⁻¹)	0.757

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.015, 0.039, 1.14
No. of reflections	1970
No. of parameters	119
No. of restraints	1
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.72, −0.80

Computer programs: APEX2 (Bruker, 2004), SAINT (Bruker, 2004), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), XtalDraw (Downs & Hall-Wallace, 2003), publCIF (Westrip, 2010).

Selected bond lengths (Å) top

Mg—O7ⁱ	2.0591 (11)	Al—OH8	1.9477 (7)
Mg—O1ⁱⁱ	2.0864 (10)	P1—O2	1.5232 (14)
Mg—O2ⁱⁱⁱ	2.1227 (10)	P1—O1	1.5278 (15)
Mg—OH9^iv	2.1729 (11)	P1—O3	1.5321 (10)
Mg—O5^v	2.2090 (12)	P1—O3^ix	1.5321 (10)
Al—O3^vi	1.8523 (11)	P2—O4	1.5083 (11)
Al—O6	1.9080 (11)	P2—O7	1.5272 (11)
Al—O5^vii	1.9287 (10)	P2—O6	1.5443 (11)
Al—OH9	1.9397 (11)	P2—O5	1.5680 (10)
Al—OH9^viii	1.9440 (11)

Symmetry codes: (i) −x+1, y−1/2, −z+1; (ii) x, y−1, z−1; (iii) x, y−1, z; (iv) x, −y+1/2, z; (v) x, −y+1/2, z−1; (vi) −x, −y+1, −z+1; (vii) x, y, z−1; (viii) −x, −y+1, −z; (ix) x, −y+3/2, z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
OH8—H1···O6^vii	0.79 (4)	2.66 (3)	3.3180 (16)	141.9 (12)
OH9—H2···O3	0.78 (3)	1.89 (3)	2.6512 (13)	166 (3)

Symmetry code: (vii) x, y, z−1.

Acknowledgements

The authors gratefully acknowledge support of this study by the Science Foundation Arizona.

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