Lead apatites: structural variations among Pb5(BO4)3Cl with B = P (pyromorphite), As (mimetite) and V (vanadinite)

Antao, S.M.; Dhaliwal, I.

doi:10.1107/S1600577517014217

research papers

JOURNAL OF
SYNCHROTRON
RADIATION

ISSN: 1600-5775

Volume 25| Part 1| January 2018| Pages 214-221

https://doi.org/10.1107/S1600577517014217

Lead apatites: structural variations among Pb₅(BO₄)₃Cl with B = P (pyromorphite), As (mimetite) and V (vanadinite)

Sytle M. Antao ^a ^* and Inayat Dhaliwal ^a

^aDepartment of Geoscience, University of Calgary, Calgary, Alberta, Canada T2N 1N4
^*Correspondence e-mail: antao@ucalgary.ca

Edited by A. F. Craievich, University of São Paulo, Brazil (Received 5 July 2017; accepted 2 October 2017)

The crystal structure of four Pb apatite samples, Pb₅(BO₄)₃Cl, was refined with synchrotron high-resolution powder X-ray diffraction data, Rietveld refinements, space group P6₃/m and Z = 2. For this isotypic series, B = P⁵⁺ is pyromorphite, B = As⁵⁺ is mimetite and B = V⁵⁺ is vanadinite. The ionic radius for As⁵⁺ (0.355 Å) is similar to that of V⁵⁺ (0.335 Å), and this is twice as large as that for P⁵⁺ (0.170 Å). However, the c unit-cell parameter for mimetite is surprisingly different from that of vanadinite, although their unit-cell volumes, V, are almost equal to each other. No explanation was available for this peculiar c-axis value for mimetite. Structural parameters such as average 〈B—O〉 [4], 〈Pb1—O₉〉 [9] and 〈Pb2—O₆Cl₂〉 [8] distances increase linearly with V (the coordination numbers for the cations are given in square brackets). Mimetite has a short Pb2—O1 distance, so the O1 oxygen atom interacts with the 6s² lone-pair electrons of the Pb²⁺ cation that causes the Cl—Cl distance (= c/2) to increase to the largest value in the series because of repulsion, which causes the c-axis to increase anomalously. Although Pb apatite minerals occur naturally in ore deposits, they are also formed as scaly deposits in lead water pipes that give rise to lead in tap water, as was found recently in Flint, Michigan, USA. It is important to identify Pb-containing phases in water-pipe deposits.

Keywords: lead apatites; pyromorphite; mimetite; vanadinite; structure; chemistry; synchrotron high-resolution powder X-ray diffraction (HRPXRD); Rietveld refinement.

1. Introduction

Apatite is a mineral of interest in various fields because of its importance in geology and technology. Hydroxylapatite, Ca₅(PO₄)₃(OH), is well known in biological sciences because it is the main constituent of dental enamel and human bones. Apatite, Ca₅(PO₄)₃(OH,F,Cl), is the most abundant rock-forming phosphate-group mineral and is the main phosphorous host in crustal rocks (McConnell, 1973 ).

Lead apatites, Pb₅(BO₄)₃(Cl), where B = P⁵⁺ is pyromorphite, B = As⁵⁺ is mimetite and B = V⁵⁺ is vanadinite, occur in various worldwide localities and as scaly deposits in lead water pipes. Recently, the issue of lead in tap water was highlighted in Flint, Michigan, USA, where high levels of lead were recorded (Robeznieks, 2015 ). Phosphate is added to drinking water in the UK to minimize the release of lead from lead water pipes (Hopwood et al., 2016 ). The phosphate addition promotes the formation of insoluble lead apatites on the walls of the water pipes where they occur as scaly deposits. Hydroxylpyromorphite, Pb₅(PO₄)₃(OH), is the lead apatite that is used often to model lead levels in tap water. However, apatites on lead water pipes were shown to be solid solutions between pyromorphite and chlorapatite, (Ca_5–xPb_x)(PO₄)₃[(OH)_yCl_1–y] (Hopwood et al., 2016). The structure of a related lead apatite mineral, phosphohedyphane, Ca₂Pb₃(PO₄)₃Cl, is also known (Kampf et al., 2006 ). Oscillatory zoning in an arsenate mineral, erythrite, Co₃(AsO₄)₂·8H₂O, was recently discussed (Antao & Dhaliwal, 2017 ).

High ion conductivity in rare-earth silicate oxyapatites is of interest (e.g. Nakayama et al., 1995 , 1999 ; Ali et al., 2009 ). Their conductivity at relatively low temperatures is of potential benefit for electrolyte materials in solid oxide fuel cells (Fergus, 2006 ). There is no rigorous explanation as to why only oxide ions in rare-earth silicate oxyapatites can move freely inside the channel whereas other ions [F, Cl and (OH)] in apatites were found to be localized at the (0,0,0) or (0,0,z) position.

Studies on the crystal chemistry of apatite supergroup minerals began with the determination of the structure of fluorapatite by Mehmel (1930 ) and Náray-Szabó (1930 ) and continue to recent times (e.g. Okudera, 2013 , and references therein). The crystal chemistry of apatites has been described in a few reviews (Elliott et al., 2002 ; White & Zhili, 2003 ; Pasero et al., 2010 ).

Based on other apatite-group minerals, pyromorphite was assumed to have hexagonal space group P6₃/m (Hendricks et al., 1932 ). The structure was refined to an R-factor of 12% by using visual estimates of intensities from precession photographs (Trotter & Barnes, 1958 ). The pyromorphite structure was refined with mixed isotropic and anisotropic displacement parameters (Dai & Hughes, 1989 ). Thereafter, the pyromorphite structure was refined with anisotropic displacement parameters (ADPs) (e.g. Akao et al., 1989 ; Hashimoto & Matsumoto, 1998 ; Laufek et al., 2006 ; Mills et al., 2012 ). The mimetite structure was refined by Calos et al. (1990 ) and that of vanadinite by Laufek et al. (2006). The structure of all three Pb apatites, using duplicate samples, was recently refined with ADPs (Okudera, 2013).

The general formula for the lead apatite isotypic series is Pb₅(BO₄)₃Cl, Z = 2, space group P6₃/m, with B = P⁵⁺ (pyromorphite), V⁵⁺ (vanadinite) and As⁵⁺ (mimetite). In these isomorphs, the O atoms occupy special positions, O1 and O2, and a general position, O3. The divalent Pb1 and Pb2 cation sites are at the 4f and 6h positions, respectively. The Cl anion occurs at the 2b position (0,0,0). The Pb1 site is coordinated by nine O atoms of six BO₄ tetrahedral groups. The Pb2 site is eight-coordinated by six O and two Cl atoms. The Cl atom is octahedrally coordinated by six Pb2 atoms and each O atom is tetrahedrally coordinated by one B and three Pb atoms (Fig. 1). The Pb2 site is commonly found in an off-centred coordination environment in lead-containing apatites (Rouse et al., 1984 ; Kampf et al., 2006).

Figure 1
Structure of vanadinite (space group P6₃/m) projected down [001]. The structure contains VO₄ tetrahedra (grey) and Pb1O₉ polyhedra (orange). The Pb2O₆Cl₂ polyhedra are not shown. The Cl atoms (blue) are in the 6₃ channels and form Cl—Pb2₆ octahedra (blue). The Pb2 sites are shown in red and O sites in black. The hexagonal unit-cell edges are outlined.

In the isotypic Pb apatites, the main difference is in the effective ionic radius (IR) of the B tetrahedral cation (P⁵⁺ = 0.170, V⁵⁺ = 0.335, As⁵⁺ = 0.355 Å and O²⁻ = 1.380 Å; Shannon, 1976 ). Based on IR, one may expect the unit-cell parameters for the As and V apatites to be nearly equal, but their c parameters are quite different. The reason for this difference is not known. Based on radii sum, one may also expect distances close to the following: P—O = 1.550, V—O = 1.735 and As—O = 1.715 Å. However, experimentally, P—O = 1.542 (8), V—O = 1.710 (12) and As—O = 1.664 (16) Å (Okudera, 2013), so there appears to be significant differences for both the V—O and As—O distances. Based on IR, the unit-cell volume for vanadinite is expected to be slightly smaller than mimetite, but the opposite is found. Moreover, significant differences occur for the c unit-cell parameter between mimetite and vanadinite although the IR for As and V are nearly the same. The reasons for these discrepancies are not clear and will be examined in this study.

There are some experimental difficulties associated with structure refinements of lead apatites, despite the availability of high-quality museum specimens. X-ray scattering is dominated by highly absorbing Pb atoms among lighter atoms and the interaction of V atoms with neutrons is negligible. As a result, published crystal structure refinements for all Pb apatites contain errors for positional coordinates in the third decimal place for the light O atoms, so errors occur in the second decimal place for bond distances (e.g. Flis et al., 2010 ; Okudera, 2013). Therefore, despite successful structure refinements for Pb apatites, the errors are still large. However, synchrotron high-resolution powder X-ray diffraction (HRPXRD) data were successfully used to refine the crystal structures of Pb-containing materials such as PbCO₃ and PbSO₄ (Antao & Hassan, 2009 ; Antao, 2012 ).

The study examines the crystal structure of Pb apatites (pyromorphite, mimetite and vanadinite) using Rietveld structure refinements and HRPXRD data. The reason for the unusual unit-cell parameter for mimetite is explained based on Cl—Cl repulsion arising from interactions of the O1 atom with the 6s² lone-pair electrons on the Pb²⁺ cation. Structural variations among Pb apatites are discussed.

2. Experimental methods

2.1. Sample locality and description

Experiments were performed on samples of pyromorphite from (1) the Daoping Mine, Gunagxi Province, China, and (2) Ontario, Canada; (3) mimetite from the Pingtouling Mine, Guangdong, China, and (4) vanadinite from Mibladén, Morocco. All samples contain euhedral crystals with well developed faces. The colours of the crystals are (1) pale green, (2) yellow, (3) orange and (4) red. Except for the Ontario sample, single-crystal structure refinements of samples from localities (1), (3) and (4) above were carried out (e.g. Laufek et al., 2006; Okudera, 2013). The pyromorphite sample used by Dai & Hughes (1989) was from Globe, Arizona, USA, and their vanadinite was from New South Wales, Australia. A mimetite sample from Durango, Mexico, was studied by Dai et al. (1991 ). Moreover, previous results from single-crystal and Rietvield structure refinements are compared in this study.

2.2. Electron-probe micro-analyzer

Quantitative chemical compositions and backscattered electron images were collected with a Jeol JXA-8200 WD-ED electron-probe micro-analyzer (EPMA). The Jeol operating program on a Solaris platform was used for ZAF correction and data reduction. The wavelength-dispersive operating conditions were 15 kV accelerating voltage, 20 nA beam current and 5 µm beam diameter. Kα radiation and the following standards were used: gallium arsenide (As), vanadium oxide (V), pyromorphite (Pb, P), scapolite (Cl), hornblende (Fe, Na, Ca), cobalt (Co), nickel oxide (Ni), zinc oxide (Zn), barite (Ba) and strontianite (Sr). The EPMA results are listed in Table 1. The chemical composition of the Pb apatite samples are close to their ideal chemical formulae, which were used in previous structure refinements (see, for example, Okudera, 2013).

Table 1
Chemical analyses for Pb apatite samples with formula M₅(BO₄)₃Cl

Wt% sample	(1) Pyromorphite (China)	(2) Pyromorphite (Ontario)	(3) Mimetite (China)	(4) Vanadinite (Morocco)
PbO wt%	82.14	81.56	74.24	78.43
FeO	0.01	0.01	0.00	0.01
CoO	0.01	0.01	0.03	0.00
NiO	0.00	0.03	0.01	0.02
BaO	0.49	0.90	0.17	0.13
ZnO	0.02	0.00	0.05	0.03
CaO	0.08	0.36	0.01	0.01
Na₂O	0.00	0.01	0.01	0.02
SrO	0.00	0.00	0.01	0.00
P₂O₅	15.87	16.09	0.06	0.46
As₂O₅	0.00	0.00	23.01	0.00
V₂O₅	0.03	0.04	0.03	18.72
Cl	2.65	2.68	2.38	2.51
	101.30	101.69	100.01	100.34
—O≡Cl	0.60	0.60	0.54	0.57
Total	100.70	101.09	99.47	99.77

	Numbers of ions on the basis of 16 (M + B)
Pb cations	9.863	9.656	9.912	9.934
Fe	0.002	0.002	0.000	0.004
Co	0.005	0.003	0.012	0.001
Ni	0.001	0.009	0.002	0.008
Ba	0.085	0.155	0.033	0.024
Zn	0.005	0.000	0.020	0.009
Ca	0.039	0.170	0.006	0.002
Na	0.000	0.005	0.012	0.018
Sr	0.000	0.000	0.003	0.000
ΣM	10.000	10.000	10.000	10.000

P	5.991	5.989	0.025	0.180
As	0.000	0.000	5.966	0.000
V	0.009	0.011	0.009	5.820
ΣB	6.000	6.000	6.000	6.000

Cl	2.000	2.000	2.000	2.000

2.3. Synchrotron high-resolution powder X-ray diffraction

The samples were studied using HRPXRD that was performed at beamline 11-BM, Advanced Photon Source, Argonne National Laboratory, USA. A small fragment (about 2 mm in diameter) of the sample was crushed to a fine powder using an agate mortar and pestle. The crushed sample was loaded into a Kapton capillary (0.8 mm internal diameter) and rotated during the experiment at a rate of 90 rotations per second. The data were collected at 23°C to a maximum 2θ of about 50° with a step size of 0.001° and a step time of 0.1 s per step. The HRPXRD traces were collected with a unique multi-analyzer detection assembly consisting of 12 independent silicon (111) crystal analyzers and LaCl₃ scintillation detectors that reduce the angular range to be scanned and allow rapid acquisition of data. A silicon (NIST 640c) and alumina (NIST 676a) standard (ratio of $[{1\over3}{\rm{Si}}:{2\over3}{\rm{Al}}_2{\rm{O}}_3]$ by weight) was used to calibrate the instrument and refine the monochromatic wavelength used in the experiment (see Table 2). Additional details of the experimental setup are given elsewhere (Antao et al., 2008 ; Lee et al., 2008 ; Wang et al., 2008 ). Similar experiments were successfully used to examine other minerals (e.g. Antao et al., 2002 ; Antao & Hassan, 2002 ; Ehm et al., 2007 ; Skinner et al., 2012 ).

Table 2
HRPXRD data and Rietveld refinement statistical indicators

	(1) Pyromorphite (China)	(2) Pyromorphite (Ontario)	(3) Mimetite (China)	(4) Vanadinite (Morocco)	(4) − (3)
a (Å)	9.96350 (3)	9.99496 (3)	10.24824 (3)	10.32465 (3)	0.07641 (4)
c (Å)	7.32427 (1)	7.33997 (2)	7.45340 (2)	7.34508 (2)	−0.10832 (3)
V (Å³)	629.678 (3)	635.019 (3)	677.927 (3)	678.075 (3)	0.148 (4)
Reduced χ²	1.747	1.548	1.863	1.002
R(F²)†	0.0774	0.0752	0.0768	0.0541
Data points	42502	37399	37528	38000
N_obs	1563	1136	1232	1236
λ (Å)	0.41323 (2)	0.41330 (2)	0.41421 (2)	0.41397 (2)

†R(F²) = overall R structure factor based on observed and calculated structure amplitudes = [∑(F_o² − F_c²)/∑(F_o²)]^1/2. 2θ range = 2.5–40.0°. Sample (1) is more crystalline than sample (2), so it has a much larger N_obs value, and the errors for the structural parameters are much smaller.

2.4. Rietveld structure refinements

The HRPXRD traces were modelled using the Rietveld method (Rietveld, 1969 ), as implemented in the GSAS program (Larson & Von Dreele, 2000 ), and using the EXPGUI interface (Toby, 2001 ). Scattering curves for neutral atoms were used in all refinements. For the structure of Pb apatite, the starting atom coordinates, unit-cell parameters and space group P6₃/m were taken from Hughes et al. (1989 ).

In the GSAS program, the reflection-peak profiles were fitted using a type-3 profile (pseudo-Voigt; Caglioti et al., 1958 ; Thompson et al., 1987 ). The background was modelled with a Chebyschev polynomial (eight terms). A full-matrix least-squares refinement varying a scale factor, unit-cell parameters, zero shift, atom coordinates and isotropic displacement parameters converged rapidly. The number of data points and the number of observed reflections in the HRPXRD trace for each sample are given in Table 2. Synchrotron powder X-ray diffraction patterns are shown in Fig. 2. Table 2 contains the Rietveld refinement statistical indicators and unit-cell parameters. The atom coordinates are given in Table 3. Some site occupancy factors were refined and those for the O atoms were fixed (Table 3). Selected bond distances and angles are given in Table 4.

Table 3
Atom coordinates†, isotropic displacement parameters (U × 10² Å²) and site occupancy factors (sofs)

Site		(1) Pyromorphite (China)	(2) Pyromorphite (Ontario)	(3) Mimetite (China)	(4) Vanadinite (Morocco)
Pb1	x	1/3	1/3	1/3	1/3
	y	2/3	2/3	2/3	2/3
	z	0.0039 (2)	0.0051 (2)	0.0066 (2)	0.0071 (1)
	U	1.04 (1)	2.40 (2)	1.31 (2)	1.37 (1)
	sof	0.948 (5)	1.0	1.02 (1)	0.948 (9)
Pb2	x	0.25449 (7)	0.25475 (8)	0.25099 (6)	0.25512 (5)
	y	0.0055 (1)	0.0059 (1)	0.00500 (9)	0.01238 (7)
	U	1.04 (1)	2.34 (1)	1.42 (1)	1.43 (1)
	sof	0.959 (5)	1.0	1.02 (1)	0.946 (9)
B	x	0.4093 (4)	0.4099 (5)	0.4081 (1)	0.4096 (2)
	y	0.3773 (4)	0.3803 (5)	0.3838 (1)	0.3838 (2)
	U	0.77 (9)	1.5 (1)	0.70 (4)	0.46 (8)
	sof	1.0	1.0	1.04 (1)	0.94 (1)
O1	x	0.3426 (9)	0.3450 (9)	0.3207 (8)	0.3317 (9)
	y	0.4905 (8)	0.4919 (9)	0.4927 (8)	0.4979 (8)
	U	1.0 (2)	2.4 (3)	1.0 (3)	2.7 (3)
O2	x	0.5898 (9)	0.5886 (9)	0.6007 (9)	0.5984 (8)
	y	0.4778 (9)	0.4741 (9)	0.4873 (8)	0.4842 (8)
	U	1.1 (3)	1.7 (3)	2.0 (3)	1.6 (3)
O3	x	0.3639 (6)	0.3598 (8)	0.3591 (6)	0.3561 (6)
	y	0.2755 (6)	0.2698 (8)	0.2730 (6)	0.2686 (6)
	z	0.0784 (6)	0.0813 (8)	0.0649 (8)	0.0636 (7)
	U	1.6 (2)	3.0 (2)	3.9 (3)	2.1 (2)
Cl	U	1.2 (1)	1.4 (1)	1.4 (1)	1.2 (1)
	sof	0.95 (1)	1.0	0.99 (1)	0.94 (1)

†Cl is at (0, 0, 0) and z = 1/4 for Pb2, B, O1 and O2. B = P (pyromorphite), As (mimetite) and V (vanadinite). The sofs for the O atoms were fixed at 1. The sofs for the other atoms were either refined or fixed at 1.0.

Table 4
Pb apatites: selected bond distances (Å) and angles (°)

BVS was calculated with the program VaList (A. S. Wills), which is available from http://www.ccp14.ac.uk.

	(1) Pyromorphite (China)	(2) Pyromorphite (Ontario)	(3) Mimetite (China)	(4) Vanadinite (Morocco)	(4) − (3)
Pb1—O1 × 3	2.550 (6)	2.550 (7)	2.501 (5)	2.488 (5)	−0.013 (7)
Pb1—O2 × 3	2.687 (6)	2.682 (8)	2.769 (6)	2.754 (6)	−0.015 (8)
Pb1—O3 × 3	2.839 (5)	2.875 (7)	2.942 (6)	2.976 (5)	0.034 (8)
〈Pb1—O〉 [9]	2.692 (1)	2.702 (1)	2.737 (1)	2.739 (1)	0.002 (1)
BVS	2.09	2.06	1.99	2.01
Pb2—Cl × 2	3.1058 (4)	3.1150 (5)	3.1558 (3)	3.1606 (4)	0.005 (4)
Pb2—O1	3.078 (8)	3.112 (11)	3.016 (7)	3.194 (8)	0.178 (11)
Pb2—O2	2.326 (8)	2.362 (10)	2.334 (8)	2.349 (7)	0.015 (11)
Pb2—O3 × 2	2.659 (5)	2.612 (7)	2.763 (6)	2.684 (5)	−0.079 (8)
Pb2—O3′ × 2	2.627 (5)	2.646 (6)	2.577 (6)	2.556 (5)	−0.021 (8)
〈Pb2—O〉 [6]	2.663 (3)	2.665 (3)	2.672 (3)	2.671 (2)	−0.001 (4)
〈Pb2—O,Cl〉 [8]	2.773 (2)	2.778 (3)	2.793 (2)	2.793 (2)	0.000 (3)
BVS	2.00	1.98	1.92	1.96
B—O1	1.569 (9)	1.545 (13)	1.745 (7)	1.727 (8)	−0.018 (11)
B—O2	1.560 (8)	1.547 (10)	1.711 (8)	1.690 (7)	−0.021 (11)
B—O3 × 2	1.534 (5)	1.565 (7)	1.695 (6)	1.714 (5)	0.019 (8)
〈B—O〉 [4]	1.549 (3)	1.556 (5)	1.712 (3)	1.711 (3)	0.000 (5)
BVS	4.82	4.73	4.67	5.14
O1—B—O2	107.8 (5)	109.7 (7)	113.9 (4)	111.7 (4)	−2.2 (6)
O1—B—O3 × 2	112.6 (3)	114.1 (4)	110.7 (2)	112.0 (2)	1.3 (3)
O2—B—O3 × 2	106.8 (3)	107.0 (4)	106.2 (2)	107.4 (2)	1.2 (3)
O3—B—O3′	110.0 (4)	104.5 (6)	108.9 (4)	106.1 (4)	−2.8 (6)
〈O—B—O〉 [6]	109.42	109.40	109.43	109.43	0.0
BVS for Cl	1.16	1.13	1.02	1.01
Cl—Cl (= c/2)	3.66213 (1)	3.66999 (1)	3.72670 (1)	3.67254 (1)	−0.054

Figure 2
Comparison of HRPXRD traces at 23°C for Pb apatites: (a) pyromorphite, (b) mimetite and (c) vanadinite together with the calculated (continuous line) and observed (crosses) profiles. The difference curve (I_obs – I_calc) with the same intensity scale is shown at the bottom of the trace. Short vertical lines indicate allowed reflection positions. The intensities for the trace and difference curve that are above 20° 2θ are multiplied by 5. The intensity scale for mimetite is ten times those for the other samples.

3. Results and discussion

3.1. Structure of Pb apatites

This study reports Rietveld structure refinements of Pb apatite samples from some classical localities. Other researchers have also used samples from these localities, so the results from several studies can be compared. Pyromorphite and mimetite samples from China and vanadinite from Mibladén, Morocco, were also examined by other researchers (Laufek et al., 2006; Okudera, 2013). These studies reported the ideal chemical formulae Pb₅(BO₄)₃Cl based on EPMA results and the ideal formulae were used in their structure refinements. In this study, some site occupancy factors (sofs) were refined (Table 3). Our sofs agree well with our EPMA results.

The crystal structure of Pb apatite is shown in Fig. 1. The Pb1 site is surrounded by nine O atoms, and the Pb2 site is surrounded by six O atoms and two Cl atoms. The B site is surrounded by four O atoms. The bond distances and angles of the two pyromorphite samples are in good agreement (Table 4). The distortions in the BO₄ tetrahedra are similar to each other.

The structure of Pb apatite isotypes is similar to those previously reported. The minerals crystallize with the chlorapatite structure, space group P6₃/m, and the Cl atom occurs at the 2b position with no evidence of site splitting. The Pb2 site is commonly found in an off-centric coordination environment (Rouse et al., 1984; Kampf et al., 2006).

The bond-valence sums (BVS) for the Pb²⁺ and B⁵⁺ cations are close to their formal valences (Table 4). The BVS value for Cl⁻ is close to 1.0 valence unit (v.u.) for mimetite and vanadinite, but it is 1.16 v.u. for pyromorphite (Table 4). BVS values higher than 1.25 v.u. for Cl⁻ were calculated for phosphohedyphane, Ca₂Pb₃(PO₄)₃Cl (Kampf et al., 2006), Sr₂Ba₃(AsO₄)₃Cl (Đordević et al., 2008 ), synthetic alforsite, Ba₅(PO₄)₃Cl (Hata et al., 1979 ), and lower than 1.1 v.u. in Sr₅(VO₄)₃Cl (Beck et al., 2006 ).

3.2. Variations among unit-cell parameters in Pb apatites

The relationships between unit-cell parameters are shown in Fig. 3. Data from the literature are included for comparison (see Fig. 3 and its caption for references). The unit-cell parameters fall along two straight lines representing the P–As and As–V apatite series. The volumes for mimetite and vanadinite are almost equal. However, vanadinite has the largest a unit-cell parameter (Fig. 3a). The c parameter for mimetite is significantly larger than that for vanadinite, which is nearly the same as that for pyromorphite (Fig. 3b). The c/a ratio for mimetite is larger than that for vanadinite (Fig. 3c). Pyromorphite and vanadinite have similar values for the c parameter, but that for mimetite is the largest (Fig. 3d). All unit-cell data from the literature seem reasonable, including single-crystal data, so there appears to be no difficulties in obtaining good unit-cell parameters.

Figure 3
Unusual relationships among unit-cell parameters. (a) Non-linear relations occur between a and V. V is nearly the same for mimetite and vanadinite, but the latter has the largest a parameter. (b) The c parameter for mimetite is larger than that for vanadinite, which is nearly the same as that for pyromorphite. (c) Pyromorphite has the largest c/a parameter. (d) Pyromorphite and vanadinite have a similar c parameter, but that for mimetite is the largest. Our data for the pyromorphite sample from China have the smallest V, which is different from other studies for samples from this locality. Unit-cell data shown as yellow triangles are from the literature (Dai & Hughes, 1989

; Calos et al., 1990

; Dai et al., 1991

; Hashimoto & Matsumoto, 1998

; Laufek et al., 2006

; Sejkora et al., 2011

; Mills et al., 2012

The unit-cell parameters occur in three groups, which may indicate limited solid solutions in nature. However, this observation may arise from the small number of natural samples examined. The unit-cell parameters of the synthetic samples show complete solid solutions between the pyromorphite–mimetite series (Flis et al., 2010). Although complete solid solutions may be possible along the mimetite–vanadinite and pyromorphite–vanadinite joins, unit-cell data are needed for synthetic samples along these joins. In nature, solid solutions occur to a very limited extent, so samples from different localities have similar unit-cell parameters that cluster in three groups. Why is the c parameter between mimetite and vanadinite so different (0.108 Å), whereas the effective ionic radii difference between As (0.335 Å) and V (0.355 Å) is quite small (Δc = 0.020 Å)? In contrast, the c parameter between pyromorphite and mimetite differ by a similar amount (Δr = 0.113 Å), but the effective ionic radii difference between P (0.170 Å) and As (0.335 Å) is quite large (0.165 Å). The answer to this question is based on the significant differences between mimetite and vanadinite and is related to the Cl—Cl and Pb2—O1 distances, as explained below.

Our two pyromorphite samples have different unit-cell parameters. The sample from Ontario has unit-cell data that coincide with that of the synthetic end-member, but the other sample from China has the smallest V, which indicates subtle chemical differences between the two samples (Table 1).

3.3. Structural variations in Pb apatites

Linear variations of selected distances with the unit-cell volume, V, are shown in Fig. 4. The average 〈Pb1—O〉 [9] distances increase linearly with V (Fig. 4a). The Pb2—Cl distance also increases linearly with V (Fig. 4b). The Cl—Cl distance (= c/2) increases linearly with the c parameter, as expected (not shown). Both the average 〈Pb2—O〉 [6] and 〈Pb2—O₆,Cl₂〉 [8] distances increase linearly with V [Figs. 4(c) and 4(d)]. The average 〈B—O〉 distance also increases linearly with V (Fig. 4e). Both mimetite and vanadinite have similar structural parameters because the radii for As and V are nearly the same (Fig. 4f).

Figure 4
Linear variations of structural parameters. (a) The average 〈Pb1—O〉 [9] distances increase linearly with V. (b) The Pb2—Cl distance increases linearly with V. The (c) average 〈Pb2—O〉 [6] and (d) 〈Pb2—O₆,Cl₂〉 [8] distances increase linearly with V. (e) The average 〈B—O〉 distance and (f) effective ionic radii (Shannon, 1976

) increase linearly with V. Mimetite and vanadinite have similar structural parameters. Some discrepancies are observed between the present data and some of those from the literature, especially for the 〈B—O〉 distance from Hashimoto & Matsumoto (1998

) and average 〈Pb2—O〉 [6] and 〈Pb2—O,Cl〉 [8] distances from Okudera (2013

). Structural data shown as yellow triangles are from the literature (Dai & Hughes, 1989

; Calos et al., 1990

; Dai et al., 1991

; Hashimoto & Matsumoto, 1998

; Laufek et al., 2006

; Sejkora et al., 2011

; Mills et al., 2012

A regular tetrahedron has six equal angles of 109.47°. Across the series, the O—B—O angles do not vary in a systematic manner. However, their average 〈O—B—O〉 [6] angle is close to the regular tetrahedron value (Table 4).

Some discrepancies are clearly observed between the present data and those from the literature (Fig. 4). Okudera (2013) selected two crystals from each of his three samples and presented six data points (duplicate runs). Chemical analyses of crystals from the same sample are not variable, so the differences observed between his duplicate samples arise only from experimental errors. This is clearly observed for some parameters shown for mimetite and vanadinite [Figs. 4(c) and 4(d)]. Other data from the literature, indicated by triangles, are off the red trend lines for data from this study, especially for pyromorphite [Figs. 4(c) and 4(d)]. For the synthetic samples along the pyromorphite–mimetite join [Figs. 4(a), 4(c) and 4(d)], the structural data fall on black trend lines that are different from the red trend lines of this study.

In Table 4, differences between mimetite and vanadinite are shown. The largest difference is between their c unit-cell parameter, Pb2—O1, and Cl—Cl distances. The Pb2—O1 distance is short in mimetite, whereas the Cl—Cl (= c/2) distance is long. The opposite is observed for vanadinite where the Pb2—O1 distance is long and the Cl—Cl distance is short.

The coordination of the Pb2 site in vanadinite is shown together with the distances within the Pb2—O₆Cl₂ polyhedra (Fig. 5). A large open space exists between the two Cl and O1 oxygen atoms where the 6s² lone-pair electrons on the Pb²⁺ cation occurs (Kampf et al., 2006). As Pb2—O1 becomes shorter, the 6s² lone-pair electrons move towards the two Cl atoms and cause them to move apart because of Cl—Cl repulsion. The opposite is the case for vanadinite. This feature explains the different and unusual c unit-cell parameters for mimetite and vanadinite, as discussed above.

Figure 5
The coordination of the Pb2 site in vanadinite. The distances within the Pb2—O₆Cl₂ polyhedra are given. The Pb2—O1 distance is shortest in mimetite and the Cl—Cl (= c/2) distance is the longest, whereas the opposite is observed for vanadinite. Between the two Cl and O1 atoms is a large open space where the 6s² electron lone pair on the Pb²⁺ cation occurs. As Pb2—O1 becomes shorter, the 6s² lone-pair electrons move towards the two Cl atoms and cause them to move apart because of repulsion. The opposite is the case for vanadinite. This feature explains the different c unit-cell parameters for mimetite and vanadinite.

From a structural point of view, solid solutions are expected among pyromorphite, mimetite and vanadinite (Figs. 3 and 4). However, synthetic samples for the various joins are needed and the structure of such samples needs to be well characterized. An analysis of compositions of natural members of the pyromorphite–mimetite–turneaureite–chlorapatite system suggests the existence of a complete solid solution among pyromorphite, mimetite, hedyphane and phosphohedyphane [Ca₂Pb₃(PO₄)₃Cl]. No stable solid solutions appear to exist between the joins phosphohedyphane–hedyphane and chlorapatite–turneaureite in natural systems (Kampf et al., 2006).

Calcian pyromorphite has been identified as the major lead-bearing phase in mine waste soils from the South Pennine orefield, UK (Cotter-Howells et al., 1994 ), and the Charterhouse mine in the Mendip Hills, UK (Cotter-Howells & Caporn, 1996 ). In experiments on the use of apatite amendments to Pb-contaminated soil (including associated grass roots) from a residential area near Oakland, California, USA, Laperche et al. (1997 ) noted that, when the soils were treated with phosphate rock (containing fluorapatite as the major constituent), all pyromorphite formed contained significant Ca. The apparent stability in natural systems of members of the chlorapatite–pyromorphite series between pyromorphite and phosphohedyphane, but not between phosphohedyphane and chlorapatite, may have important implications for the use of apatite to reclaim Pb-contaminated waters and soils.

This study shows that HRPXRD is a powerful technique that can be used to obtain reliable structural parameters on gem-quality crystals that diffract poorly. Moreover, highly penetrating synchrotron X-rays can also be used to study samples that contain strongly absorbing atoms.

Supporting information

Crystal structure: contains datablocks global, pyromor_ch_publ. DOI: https://doi.org/10.1107/S1600577517014217/co5089sup1.cif

Crystal structure: contains datablocks global, pyromorphite_publ. DOI: https://doi.org/10.1107/S1600577517014217/co5089sup2.cif

Crystal structure: contains datablocks global, 2profs_mimetite-chin_publ. DOI: https://doi.org/10.1107/S1600577517014217/co5089sup3.cif

Crystal structure: contains datablocks global, 2profs_vanadinite_publ. DOI: https://doi.org/10.1107/S1600577517014217/co5089sup4.cif

Computing details top

Software used to prepare material for publication: PLATON (Spek, 2003).

(pyromor_ch_publ) top

Crystal data top

Cl_0.32O₄PPb_1.59	V = 629.68 (1) Å³
M_r = 2614.89	Z = 1
Hexagonal, P6₃/m	F(000) = 1097
Hall symbol: -P 6c	D_x = 6.896 Mg m⁻³
a = 9.96350 (2) Å	Synchrotron radiation
c = 7.32427 (1) Å	T = 296 K

Data collection top

11BM diffractometer	Detector resolution: 18.4 pixels mm^-1
Radiation source: synchrotron, synchrotron

Refinement top

Least-squares matrix: full	0 restraints
49498 data points	(Δ/σ)_max = 0.030
36 parameters

Special details top

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Pb1	0.33333	0.66667	0.0039 (2)	0.0104 (1)*	0.948 (5)
Pb2	0.25449 (7)	0.00550 (10)	0.25000	0.0104 (1)*	0.960 (4)
P	0.4093 (4)	0.3773 (4)	0.25000	0.0077 (9)*
Cl	0.00000	0.00000	0.00000	0.0115 (12)*	0.947 (9)
O1	0.3426 (9)	0.4905 (8)	0.25000	0.011 (2)*
O2	0.5897 (9)	0.4778 (9)	0.25000	0.011 (2)*
O3	0.3639 (6)	0.2755 (6)	0.0784 (6)	0.0155 (17)*

Geometric parameters (Å, º) top

Pb1—O1	2.550 (6)	Pb2—O3	2.659 (5)
Pb1—O2ⁱ	2.687 (10)	Pb2—O2^ix	2.326 (11)
Pb1—O1ⁱⁱ	2.550 (7)	Pb2—O3^x	2.627 (5)
Pb1—O2ⁱⁱⁱ	2.687 (7)	Pb2—O3^xi	2.627 (5)
Pb1—O1^iv	2.550 (9)	Pb2—O3^xii	2.659 (5)
Pb1—O2^v	2.687 (8)	P—O1	1.570 (10)
Pb1—O3^vi	2.839 (7)	P—O2	1.560 (10)
Pb1—O3^vii	2.839 (7)	P—O3	1.534 (5)
Pb1—O3^viii	2.839 (6)	P—O3^xii	1.534 (5)

O1—Pb1—O2ⁱ	126.9 (2)	O2^v—Pb1—O3^viii	123.3 (2)
O1—Pb1—O1ⁱⁱ	75.5 (2)	O3^vi—Pb1—O3^vii	115.62 (17)
O1—Pb1—O2ⁱⁱⁱ	90.13 (19)	O3^vi—Pb1—O3^viii	115.62 (19)
O1—Pb1—O1^iv	75.5 (3)	O3^vii—Pb1—O3^viii	115.6 (2)
O1—Pb1—O2^v	149.9 (3)	O2^ix—Pb2—O3	75.1 (3)
O1—Pb1—O3^vi	83.6 (2)	O3—Pb2—O3^x	136.69 (18)
O1—Pb1—O3^vii	146.60 (18)	O3—Pb2—O3^xi	82.08 (18)
O1—Pb1—O3^viii	74.1 (2)	O3—Pb2—O3^xii	56.41 (14)
O1ⁱⁱ—Pb1—O2ⁱ	149.9 (3)	O2^ix—Pb2—O3^x	83.39 (19)
O2ⁱ—Pb1—O2ⁱⁱⁱ	77.4 (3)	O2^ix—Pb2—O3^xi	83.39 (19)
O1^iv—Pb1—O2ⁱ	90.1 (3)	O2^ix—Pb2—O3^xii	75.1 (3)
O2ⁱ—Pb1—O2^v	77.4 (3)	O3^x—Pb2—O3^xi	132.6 (2)
O2ⁱ—Pb1—O3^vi	123.3 (2)	O3^x—Pb2—O3^xii	82.08 (18)
O2ⁱ—Pb1—O3^vii	66.9 (2)	O3^xi—Pb2—O3^xii	136.69 (18)
O2ⁱ—Pb1—O3^viii	53.3 (2)	O1—P—O2	107.7 (5)
O1ⁱⁱ—Pb1—O2ⁱⁱⁱ	126.9 (3)	O1—P—O3	112.6 (3)
O1ⁱⁱ—Pb1—O1^iv	75.5 (3)	O1—P—O3^xii	112.6 (3)
O1ⁱⁱ—Pb1—O2^v	90.1 (2)	O2—P—O3	106.8 (3)
O1ⁱⁱ—Pb1—O3^vi	74.1 (2)	O2—P—O3^xii	106.8 (3)
O1ⁱⁱ—Pb1—O3^vii	83.6 (2)	O3—P—O3^xii	110.0 (3)
O1ⁱⁱ—Pb1—O3^viii	146.6 (2)	Pb1—O1—P	132.0 (2)
O1^iv—Pb1—O2ⁱⁱⁱ	149.9 (2)	Pb1—O1—Pb1^xiii	90.0 (3)
O2ⁱⁱⁱ—Pb1—O2^v	77.4 (2)	Pb1^xiii—O1—P	132.0 (2)
O2ⁱⁱⁱ—Pb1—O3^vi	53.3 (2)	Pb1^xiv—O2—P	101.7 (3)
O2ⁱⁱⁱ—Pb1—O3^vii	123.27 (17)	Pb2^xv—O2—P	130.5 (5)
O2ⁱⁱⁱ—Pb1—O3^viii	66.9 (2)	Pb1^vi—O2—P	101.7 (3)
O1^iv—Pb1—O2^v	126.9 (3)	Pb1^xiv—O2—Pb1^vi	87.6 (3)
O1^iv—Pb1—O3^vi	146.6 (2)	Pb2—O3—P	96.8 (2)
O1^iv—Pb1—O3^vii	74.1 (2)	Pb2—O3—Pb2ⁱ	114.22 (19)
O1^iv—Pb1—O3^viii	83.6 (2)	Pb2ⁱ—O3—P	140.8 (4)
O2^v—Pb1—O3^vi	66.9 (3)	Pb1^vi—O3—P	96.2 (3)
O2^v—Pb1—O3^vii	53.3 (3)

O3^x—Pb2—O3—P	−17.4 (5)	O3—P—O1—Pb1	−45.5 (7)
O3^xi—Pb2—O3—P	−165.5 (4)	O1—P—O3—Pb2	−128.8 (4)
O3^xii—Pb2—O3—P	1.6 (3)	O2—P—O3—Pb2	113.1 (4)
O3—Pb2—O3^xii—P	−1.6 (3)	O3^xii—P—O3—Pb2	−2.4 (5)
O2—P—O1—Pb1	72.0 (5)	O3—P—O3^xii—Pb2	2.4 (5)

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

(pyromorphite_publ) top

Crystal data top

ClO₁₂P₃Pb₅	V = 635.02 (1) Å³
M_r = 1356.36	Z = 2
Hexagonal, P6₃/m	F(000) = 1136
Hall symbol: -P 6c	D_x = 7.094 Mg m⁻³
a = 9.99497 (2) Å	Synchrotron radiation
c = 7.33997 (2) Å	T = 296 K

Data collection top

11BM diffractometer	Detector resolution: 18.4 pixels mm^-1
Radiation source: synchrotron, synchrotron

Refinement top

Least-squares matrix: full	0 restraints
49497 data points	(Δ/σ)_max = 0.010
33 parameters

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Pb1	0.33333	0.66667	0.0052 (2)	0.0241 (2)*
Pb2	0.25474 (8)	0.00590 (10)	0.25000	0.0234 (1)*
Cl	0.00000	0.00000	0.00000	0.0141 (12)*
P	0.4098 (5)	0.3802 (5)	0.25000	0.0150 (12)*
O1	0.3450 (10)	0.4920 (10)	0.25000	0.023 (3)*
O2	0.5890 (10)	0.4740 (10)	0.25000	0.017 (3)*
O3	0.3596 (8)	0.2696 (8)	0.0814 (8)	0.030 (2)*

Geometric parameters (Å, º) top

Pb1—O1	2.548 (7)	Pb2—O3	2.610 (7)
Pb1—O2ⁱ	2.680 (10)	Pb2—Cl^ix	3.1150 (8)
Pb1—O1ⁱⁱ	2.548 (9)	Pb2—O2^x	2.363 (12)
Pb1—O2ⁱⁱⁱ	2.680 (7)	Pb2—O3^xi	2.646 (7)
Pb1—O1^iv	2.548 (11)	Pb2—O3^xii	2.646 (7)
Pb1—O2^v	2.680 (9)	Pb2—O3^xiii	2.610 (7)
Pb1—O3^vi	2.877 (9)	P—O1	1.547 (11)
Pb1—O3^vii	2.877 (9)	P—O2	1.552 (12)
Pb1—O3^viii	2.877 (7)	P—O3	1.565 (7)
Pb2—Cl	3.1150 (8)	P—O3^xiii	1.565 (7)

O1—Pb1—O2ⁱ	127.2 (3)	Cl^ix—Pb2—O2^x	138.34 (14)
O1—Pb1—O1ⁱⁱ	75.8 (3)	Cl^ix—Pb2—O3^xi	69.2 (2)
O1—Pb1—O2ⁱⁱⁱ	90.5 (2)	Cl^ix—Pb2—O3^xii	136.7 (2)
O1—Pb1—O1^iv	75.8 (3)	Cl^ix—Pb2—O3^xiii	69.61 (18)
O1—Pb1—O2^v	150.0 (4)	O2^x—Pb2—O3^xi	84.7 (2)
O1—Pb1—O3^vi	84.2 (3)	O2^x—Pb2—O3^xii	84.7 (2)
O1—Pb1—O3^vii	147.2 (2)	O2^x—Pb2—O3^xiii	75.2 (3)
O1—Pb1—O3^viii	74.3 (2)	O3^xi—Pb2—O3^xii	133.7 (3)
O1ⁱⁱ—Pb1—O2ⁱ	150.0 (4)	O3^xi—Pb2—O3^xiii	82.1 (2)
O2ⁱ—Pb1—O2ⁱⁱⁱ	76.5 (3)	O3^xii—Pb2—O3^xiii	137.3 (2)
O1^iv—Pb1—O2ⁱ	90.5 (3)	Pb2—Cl—Pb2ⁱ	91.18 (2)
O2ⁱ—Pb1—O2^v	76.5 (3)	Pb2—Cl—Pb2^xiv	88.82 (2)
O2ⁱ—Pb1—O3^vi	122.3 (3)	Pb2—Cl—Pb2^xv	180.00
O2ⁱ—Pb1—O3^vii	66.3 (3)	Pb2—Cl—Pb2^xvi	88.82 (2)
O2ⁱ—Pb1—O3^viii	53.5 (2)	Pb2—Cl—Pb2^xvii	91.18 (2)
O1ⁱⁱ—Pb1—O2ⁱⁱⁱ	127.2 (3)	Pb2ⁱ—Cl—Pb2^xiv	91.18 (2)
O1ⁱⁱ—Pb1—O1^iv	75.8 (3)	Pb2ⁱ—Cl—Pb2^xv	88.82 (2)
O1ⁱⁱ—Pb1—O2^v	90.5 (3)	Pb2ⁱ—Cl—Pb2^xvi	180.00
O1ⁱⁱ—Pb1—O3^vi	74.3 (3)	Pb2ⁱ—Cl—Pb2^xvii	88.82 (2)
O1ⁱⁱ—Pb1—O3^vii	84.2 (3)	Pb2^xiv—Cl—Pb2^xv	91.18 (2)
O1ⁱⁱ—Pb1—O3^viii	147.2 (2)	Pb2^xiv—Cl—Pb2^xvi	88.82 (2)
O1^iv—Pb1—O2ⁱⁱⁱ	150.0 (3)	Pb2^xiv—Cl—Pb2^xvii	180.00
O2ⁱⁱⁱ—Pb1—O2^v	76.5 (3)	Pb2^xv—Cl—Pb2^xvi	91.18 (2)
O2ⁱⁱⁱ—Pb1—O3^vi	53.5 (3)	Pb2^xv—Cl—Pb2^xvii	88.82 (2)
O2ⁱⁱⁱ—Pb1—O3^vii	122.3 (2)	Pb2^xvi—Cl—Pb2^xvii	91.18 (2)
O2ⁱⁱⁱ—Pb1—O3^viii	66.3 (3)	O1—P—O2	109.7 (6)
O1^iv—Pb1—O2^v	127.2 (3)	O1—P—O3	114.1 (4)
O1^iv—Pb1—O3^vi	147.2 (3)	O1—P—O3^xiii	114.1 (4)
O1^iv—Pb1—O3^vii	74.3 (3)	O2—P—O3	107.0 (4)
O1^iv—Pb1—O3^viii	84.2 (3)	O2—P—O3^xiii	107.0 (4)
O2^v—Pb1—O3^vi	66.3 (3)	O3—P—O3^xiii	104.5 (4)
O2^v—Pb1—O3^vii	53.5 (3)	Pb1—O1—P	132.4 (3)
O2^v—Pb1—O3^viii	122.3 (2)	Pb1—O1—Pb1^xviii	89.7 (3)
O3^vi—Pb1—O3^vii	115.3 (2)	Pb1^xviii—O1—P	132.4 (3)
O3^vi—Pb1—O3^viii	115.3 (3)	Pb1^xix—O2—P	103.5 (3)
O3^vii—Pb1—O3^viii	115.3 (3)	Pb2^xx—O2—P	128.0 (6)
Cl—Pb2—O3	69.61 (18)	Pb1^vi—O2—P	103.5 (3)
Cl—Pb2—Cl^ix	72.18 (2)	Pb1^xix—O2—Pb2^xx	112.9 (3)
Cl—Pb2—O2^x	138.34 (14)	Pb1^xix—O2—Pb1^vi	88.7 (3)
Cl—Pb2—O3^xi	136.7 (2)	Pb1^vi—O2—Pb2^xx	112.9 (3)
Cl—Pb2—O3^xii	69.2 (2)	Pb2—O3—P	99.4 (3)
Cl—Pb2—O3^xiii	102.13 (18)	Pb2—O3—Pb2ⁱ	115.7 (3)
Cl^ix—Pb2—O3	102.13 (18)	Pb1^vi—O3—Pb2	100.0 (3)
O2^x—Pb2—O3	75.2 (3)	Pb2ⁱ—O3—P	138.1 (4)
O3—Pb2—O3^xi	137.3 (2)	Pb1^vi—O3—P	95.1 (4)
O3—Pb2—O3^xii	82.1 (2)	Pb1^vi—O3—Pb2ⁱ	100.3 (2)
O3—Pb2—O3^xiii	56.60 (19)

Cl—Pb2—O3—P	123.2 (5)	O3—P—O1—Pb1	−47.3 (9)
O3^xi—Pb2—O3—P	−14.8 (7)	O1—P—O3—Pb2	−128.5 (4)
O3^xii—Pb2—O3—P	−166.1 (5)	O2—P—O3—Pb2	109.9 (4)
O3^xiii—Pb2—O3—P	2.3 (4)	O3^xiii—P—O3—Pb2	−3.3 (6)
O3—Pb2—O3^xiii—P	−2.3 (4)	O3—P—O3^xiii—Pb2	3.3 (6)
O2—P—O1—Pb1	72.7 (6)

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

(2profs_mimetite-chin_publ) top

Crystal data top

As₃ClO₁₂Pb₅	V = 677.93 (1) Å³
M_r = 1488.21	Z = 2
Hexagonal, P6₃/m	F(000) = 1244
Hall symbol: -P 6c	D_x = 7.291 Mg m⁻³
a = 10.24823 (2) Å	Synchrotron radiation
c = 7.45339 (2) Å	T = 296 K

Data collection top

11BM diffractometer	Detector resolution: 18.4 pixels mm^-1
Radiation source: synchrotron, synchrotron

Refinement top

Least-squares matrix: full	0 restraints
49497 data points	(Δ/σ)_max = 0.220
35 parameters

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Pb1	0.33333	0.66667	0.5064 (2)	0.0139 (1)*
Pb2	0.00500 (9)	0.25099 (6)	0.25000	0.0139 (1)*
As	0.38380 (10)	0.40810 (10)	0.25000	0.0047 (3)*
Cl	0.00000	0.00000	0.00000	0.0141 (10)*
O1	0.4932 (8)	0.3226 (8)	0.25000	0.013 (2)*
O2	0.4853 (8)	0.5986 (9)	0.25000	0.022 (2)*
O3	0.2735 (6)	0.3588 (6)	0.0666 (7)	0.042 (2)*

Geometric parameters (Å, º) top

Pb1—As	3.5088 (12)	Pb2—Cl	3.1558 (5)
Pb1—O2	2.766 (7)	Pb2—O3	2.761 (6)
Pb1—O1ⁱ	2.505 (6)	Pb2—Clⁱ	3.1558 (5)
Pb1—Asⁱⁱ	3.5088 (13)	Pb2—O3ⁱ	2.587 (6)
Pb1—O2ⁱⁱ	2.766 (8)	Pb2—O1^viii	3.031 (10)
Pb1—O1ⁱⁱⁱ	2.505 (6)	Pb2—O2^iv	2.353 (7)
Pb1—As^iv	3.5088 (15)	Pb2—O3^vii	2.761 (6)
Pb1—O2^iv	2.766 (8)	Pb2—O3^ix	2.587 (6)
Pb1—O1^v	2.505 (7)	As—O1	1.734 (9)
Pb1—O3^vi	2.948 (9)	As—O2	1.692 (8)
Pb1—O3^vii	2.948 (6)	As—O3	1.682 (6)
Pb2—As	3.3782 (14)	As—O3^vii	1.682 (6)

As—Pb1—O2	28.24 (17)	O2^iv—Pb2—O3	74.8 (3)
As—Pb1—O1ⁱ	98.98 (18)	O3—Pb2—O3^vii	59.36 (17)
As—Pb1—Asⁱⁱ	93.16 (3)	O3—Pb2—O3^ix	80.9 (2)
As—Pb1—O2ⁱⁱ	99.62 (17)	Clⁱ—Pb2—O3ⁱ	70.93 (15)
As—Pb1—O1ⁱⁱⁱ	93.36 (16)	Clⁱ—Pb2—O1^viii	102.36 (15)
As—Pb1—As^iv	93.16 (4)	Clⁱ—Pb2—O2^iv	137.93 (15)
As—Pb1—O2^iv	65.5 (2)	Clⁱ—Pb2—O3^vii	68.93 (11)
As—Pb1—O1^v	165.88 (18)	Clⁱ—Pb2—O3^ix	138.64 (12)
As—Pb1—O3^vi	121.64 (11)	O1^viii—Pb2—O3ⁱ	68.11 (18)
As—Pb1—O3^vii	28.55 (11)	O2^iv—Pb2—O3ⁱ	83.22 (17)
O1ⁱ—Pb1—O2	125.5 (3)	O3ⁱ—Pb2—O3^vii	80.9 (2)
Asⁱⁱ—Pb1—O2	65.48 (16)	O3ⁱ—Pb2—O3^ix	131.6 (3)
O2—Pb1—O2ⁱⁱ	77.5 (2)	O1^viii—Pb2—O2^iv	97.7 (4)
O1ⁱⁱⁱ—Pb1—O2	92.0 (2)	O1^viii—Pb2—O3^vii	148.86 (13)
As^iv—Pb1—O2	99.62 (15)	O1^viii—Pb2—O3^ix	68.11 (18)
O2—Pb1—O2^iv	77.5 (3)	O2^iv—Pb2—O3^vii	74.8 (3)
O1^v—Pb1—O2	152.4 (3)	O2^iv—Pb2—O3^ix	83.22 (17)
O2—Pb1—O3^vi	125.29 (18)	O3^vii—Pb2—O3^ix	138.2 (2)
O2—Pb1—O3^vii	56.3 (2)	Pb1—As—Pb2	77.98 (2)
Asⁱⁱ—Pb1—O1ⁱ	165.88 (13)	Pb1—As—O1	139.31 (14)
O1ⁱ—Pb1—O2ⁱⁱ	152.4 (3)	Pb1—As—O2	50.7 (2)
O1ⁱ—Pb1—O1ⁱⁱⁱ	73.3 (3)	Pb1—As—O3	109.8 (2)
As^iv—Pb1—O1ⁱ	93.4 (2)	Pb1—As—Pb1^vi	66.00 (3)
O1ⁱ—Pb1—O2^iv	92.0 (2)	Pb1—As—O3^vii	56.88 (19)
O1ⁱ—Pb1—O1^v	73.3 (2)	Pb2—As—O1	129.7 (3)
O1ⁱ—Pb1—O3^vi	86.8 (3)	Pb2—As—O2	116.6 (3)
O1ⁱ—Pb1—O3^vii	70.5 (2)	Pb2—As—O3	54.4 (2)
Asⁱⁱ—Pb1—O2ⁱⁱ	28.2 (2)	Pb1^vi—As—Pb2	77.98 (2)
Asⁱⁱ—Pb1—O1ⁱⁱⁱ	98.98 (16)	Pb2—As—O3^vii	54.4 (2)
Asⁱⁱ—Pb1—As^iv	93.16 (4)	O1—As—O2	113.8 (4)
Asⁱⁱ—Pb1—O2^iv	99.62 (13)	O1—As—O3	110.8 (2)
Asⁱⁱ—Pb1—O1^v	93.36 (19)	Pb1^vi—As—O1	139.31 (14)
Asⁱⁱ—Pb1—O3^vi	93.00 (11)	O1—As—O3^vii	110.8 (2)
Asⁱⁱ—Pb1—O3^vii	121.64 (12)	O2—As—O3	106.2 (3)
O1ⁱⁱⁱ—Pb1—O2ⁱⁱ	125.5 (3)	Pb1^vi—As—O2	50.7 (2)
As^iv—Pb1—O2ⁱⁱ	65.5 (2)	O2—As—O3^vii	106.2 (3)
O2ⁱⁱ—Pb1—O2^iv	77.5 (2)	Pb1^vi—As—O3	56.88 (19)
O1^v—Pb1—O2ⁱⁱ	92.0 (2)	O3—As—O3^vii	108.7 (3)
O2ⁱⁱ—Pb1—O3^vi	66.1 (3)	Pb1^vi—As—O3^vii	109.8 (2)
O2ⁱⁱ—Pb1—O3^vii	125.29 (19)	Pb2—Cl—Pb2^x	91.32 (2)
As^iv—Pb1—O1ⁱⁱⁱ	165.88 (16)	Pb2—Cl—Pb2^viii	88.69 (2)
O1ⁱⁱⁱ—Pb1—O2^iv	152.4 (2)	Pb2—Cl—Pb2^xi	180.00
O1ⁱⁱⁱ—Pb1—O1^v	73.3 (3)	Pb2—Cl—Pb2^xii	88.69 (2)
O1ⁱⁱⁱ—Pb1—O3^vi	142.32 (19)	Pb2—Cl—Pb2^xiii	91.32 (2)
O1ⁱⁱⁱ—Pb1—O3^vii	86.8 (2)	Pb2^x—Cl—Pb2^viii	91.32 (2)
As^iv—Pb1—O2^iv	28.2 (2)	Pb2^x—Cl—Pb2^xi	88.69 (2)
As^iv—Pb1—O1^v	99.0 (2)	Pb2^x—Cl—Pb2^xii	180.00
As^iv—Pb1—O3^vi	28.55 (10)	Pb2^x—Cl—Pb2^xiii	88.69 (2)
As^iv—Pb1—O3^vii	93.00 (13)	Pb2^viii—Cl—Pb2^xi	91.32 (2)
O1^v—Pb1—O2^iv	125.5 (3)	Pb2^viii—Cl—Pb2^xii	88.69 (2)
O2^iv—Pb1—O3^vi	56.3 (3)	Pb2^viii—Cl—Pb2^xiii	180.00
O2^iv—Pb1—O3^vii	66.1 (2)	Pb2^xi—Cl—Pb2^xii	91.32 (2)
O1^v—Pb1—O3^vi	70.5 (2)	Pb2^xi—Cl—Pb2^xiii	88.69 (2)
O1^v—Pb1—O3^vii	142.3 (2)	Pb2^xii—Cl—Pb2^xiii	91.32 (2)
O3^vi—Pb1—O3^vii	116.67 (17)	Pb1^xiv—O1—As	127.0 (2)
As—Pb2—Cl	86.27 (2)	Pb2^xii—O1—As	99.6 (3)
As—Pb2—O3	29.69 (12)	Pb1^xv—O1—As	127.0 (2)
As—Pb2—Clⁱ	86.27 (2)	Pb1^xiv—O1—Pb2^xii	103.3 (2)
As—Pb2—O3ⁱ	109.55 (17)	Pb1^xiv—O1—Pb1^xv	92.9 (3)
As—Pb2—O1^viii	169.24 (19)	Pb1^xv—O1—Pb2^xii	103.3 (2)
As—Pb2—O2^iv	71.5 (3)	Pb1—O2—As	101.1 (3)
As—Pb2—O3^vii	29.69 (12)	Pb1—O2—Pb2ⁱⁱ	115.5 (2)
As—Pb2—O3^ix	109.55 (17)	Pb1—O2—Pb1^vi	87.4 (3)
Cl—Pb2—O3	68.93 (11)	Pb2ⁱⁱ—O2—As	128.1 (5)
Cl—Pb2—Clⁱ	72.38 (1)	Pb1^vi—O2—As	101.1 (3)
Cl—Pb2—O3ⁱ	138.64 (12)	Pb1^vi—O2—Pb2ⁱⁱ	115.5 (2)
Cl—Pb2—O1^viii	102.36 (15)	Pb2—O3—As	95.9 (2)
Cl—Pb2—O2^iv	137.93 (15)	Pb2—O3—Pb2^xiii	115.1 (2)
Cl—Pb2—O3^vii	103.02 (13)	Pb1^vi—O3—Pb2	98.7 (2)
Cl—Pb2—O3^ix	70.93 (15)	Pb2^xiii—O3—As	140.5 (4)
Clⁱ—Pb2—O3	103.02 (13)	Pb1^vi—O3—As	94.6 (2)
O3—Pb2—O3ⁱ	138.2 (2)	Pb1^vi—O3—Pb2^xiii	103.55 (18)
O1^viii—Pb2—O3	148.86 (13)

O2—Pb1—As—Pb2	−139.9 (3)	Cl—Pb2—O3—As	−122.3 (2)
O2—Pb1—As—O1	81.2 (4)	O3ⁱ—Pb2—O3—As	18.6 (4)
O2—Pb1—As—O3	−95.1 (4)	O3^vii—Pb2—O3—As	−1.75 (19)
O3^vi—Pb1—As—O3	11.6 (2)	O3^ix—Pb2—O3—As	164.7 (3)
O3^vii—Pb1—As—O3	99.9 (3)	O3—Pb2—O3^vii—Pb1	97.3 (2)
Cl—Pb2—As—Pb1	177.56 (2)	O3—Pb2—O3^vii—As	1.75 (19)
Cl—Pb2—As—O1	−36.28 (1)	Pb2—As—O2—Pb1	44.75 (18)
Cl—Pb2—As—O2	143.72 (1)	O1—As—O2—Pb1	−135.25 (18)
Cl—Pb2—As—O3	52.2 (2)	O3—As—O2—Pb1	102.6 (3)
O3—Pb2—As—Pb1	125.4 (2)	Pb1—As—O3—Pb2	−57.97 (18)
O3—Pb2—As—O1	−88.5 (2)	O1—As—O3—Pb2	124.6 (3)
O3—Pb2—As—O2	91.5 (2)	O2—As—O3—Pb2	−111.4 (3)
O3—Pb2—As—O3^vii	−177.0 (3)	O3^vii—As—O3—Pb2	2.6 (3)
O3ⁱ—Pb2—As—O3	−167.0 (3)	O3—As—O3^vii—Pb1	−101.9 (2)
O3^vii—Pb2—As—O3	177.0 (3)	O3—As—O3^vii—Pb2	−2.6 (3)
O3^ix—Pb2—As—O3	−16.1 (3)

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

(2profs_vanadinite_publ) top

Crystal data top

ClO₁₂Pb₅V₃	V = 678.07 (1) Å³
M_r = 1416.27	Z = 2
Hexagonal, P6₃/m	F(000) = 1184
Hall symbol: -P 6c	D_x = 6.937 Mg m⁻³
a = 10.32464 (2) Å	Synchrotron radiation
c = 7.34508 (2) Å	T = 296 K

Data collection top

11BM diffractometer	Detector resolution: 18.4 pixels mm^-1
Radiation source: synchrotron, synchrotron

Refinement top

Least-squares matrix: full	0 restraints
49495 data points	(Δ/σ)_max = 0.130
35 parameters

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Pb1	0.33333	0.66667	0.00710 (10)	0.0137 (1)*
Pb2	0.25517 (5)	0.01245 (7)	0.25000	0.0142 (1)*
V	0.4096 (2)	0.3838 (2)	0.25000	0.0061 (6)*
Cl	0.00000	0.00000	0.00000	0.0125 (8)*
O1	0.3321 (9)	0.4985 (8)	0.25000	0.020 (3)*
O2	0.5987 (8)	0.4839 (8)	0.25000	0.008 (2)*
O3	0.3567 (6)	0.2690 (6)	0.0633 (6)	0.0136 (17)*

Geometric parameters (Å, º) top

Pb1—O1	2.485 (6)	Pb2—O3	2.687 (5)
Pb1—O2ⁱ	2.751 (9)	Pb2—Cl^ix	3.1608 (5)
Pb1—O1ⁱⁱ	2.485 (7)	Pb2—O2^x	2.351 (10)
Pb1—O2ⁱⁱⁱ	2.751 (6)	Pb2—O3^xi	2.556 (5)
Pb1—O1^iv	2.485 (9)	Pb2—O3^xii	2.556 (5)
Pb1—O2^v	2.751 (7)	Pb2—O3^xiii	2.687 (5)
Pb1—O3^vi	2.971 (7)	V—O1	1.729 (9)
Pb1—O3^vii	2.971 (7)	V—O2	1.692 (9)
Pb1—O3^viii	2.971 (6)	V—O3	1.714 (5)
Pb2—Cl	3.1608 (5)	V—O3^xiii	1.714 (5)

O1—Pb1—O2ⁱ	126.7 (2)	Cl^ix—Pb2—O2^x	139.71 (11)
O1—Pb1—O1ⁱⁱ	74.2 (3)	Cl^ix—Pb2—O3^xi	71.01 (16)
O1—Pb1—O2ⁱⁱⁱ	90.67 (19)	Cl^ix—Pb2—O3^xii	136.11 (17)
O1—Pb1—O1^iv	74.2 (3)	Cl^ix—Pb2—O3^xiii	69.51 (14)
O1—Pb1—O2^v	150.4 (3)	O2^x—Pb2—O3^xi	84.18 (19)
O1—Pb1—O3^vi	84.8 (2)	O2^x—Pb2—O3^xii	84.18 (19)
O1—Pb1—O3^vii	142.77 (19)	O2^x—Pb2—O3^xiii	76.3 (3)
O1—Pb1—O3^viii	70.7 (2)	O3^xi—Pb2—O3^xii	128.4 (2)
O1ⁱⁱ—Pb1—O2ⁱ	150.4 (3)	O3^xi—Pb2—O3^xiii	82.31 (18)
O2ⁱ—Pb1—O2ⁱⁱⁱ	78.1 (2)	O3^xii—Pb2—O3^xiii	141.74 (19)
O1^iv—Pb1—O2ⁱ	90.7 (3)	O1—V—O2	111.7 (4)
O2ⁱ—Pb1—O2^v	78.1 (2)	O1—V—O3	112.2 (3)
O2ⁱ—Pb1—O3^vi	126.3 (2)	O1—V—O3^xiii	112.2 (3)
O2ⁱ—Pb1—O3^vii	66.0 (2)	O2—V—O3	107.1 (3)
O2ⁱ—Pb1—O3^viii	57.05 (19)	O2—V—O3^xiii	107.1 (3)
O1ⁱⁱ—Pb1—O2ⁱⁱⁱ	126.7 (3)	O3—V—O3^xiii	106.3 (3)
O1ⁱⁱ—Pb1—O1^iv	74.2 (3)	Pb2—Cl—Pb2ⁱ	90.36 (2)
O1ⁱⁱ—Pb1—O2^v	90.7 (2)	Pb2—Cl—Pb2^xiv	89.64 (2)
O1ⁱⁱ—Pb1—O3^vi	70.7 (2)	Pb2—Cl—Pb2^xv	180.00
O1ⁱⁱ—Pb1—O3^vii	84.8 (3)	Pb2—Cl—Pb2^xvi	89.64 (2)
O1ⁱⁱ—Pb1—O3^viii	142.8 (2)	Pb2—Cl—Pb2^xvii	90.36 (2)
O1^iv—Pb1—O2ⁱⁱⁱ	150.4 (2)	Pb2ⁱ—Cl—Pb2^xiv	90.36 (2)
O2ⁱⁱⁱ—Pb1—O2^v	78.1 (2)	Pb2ⁱ—Cl—Pb2^xv	89.64 (2)
O2ⁱⁱⁱ—Pb1—O3^vi	57.1 (2)	Pb2ⁱ—Cl—Pb2^xvi	180.00
O2ⁱⁱⁱ—Pb1—O3^vii	126.31 (15)	Pb2ⁱ—Cl—Pb2^xvii	89.64 (2)
O2ⁱⁱⁱ—Pb1—O3^viii	66.0 (2)	Pb2^xiv—Cl—Pb2^xv	90.36 (2)
O1^iv—Pb1—O2^v	126.7 (3)	Pb2^xiv—Cl—Pb2^xvi	89.64 (2)
O1^iv—Pb1—O3^vi	142.8 (2)	Pb2^xiv—Cl—Pb2^xvii	180.00
O1^iv—Pb1—O3^vii	70.7 (2)	Pb2^xv—Cl—Pb2^xvi	90.36 (2)
O1^iv—Pb1—O3^viii	84.8 (2)	Pb2^xv—Cl—Pb2^xvii	89.64 (2)
O2^v—Pb1—O3^vi	66.0 (2)	Pb2^xvi—Cl—Pb2^xvii	90.36 (2)
O2^v—Pb1—O3^vii	57.1 (2)	Pb1—O1—V	129.5 (3)
O2^v—Pb1—O3^viii	126.31 (17)	Pb1—O1—Pb1^xviii	91.8 (3)
O3^vi—Pb1—O3^vii	117.04 (17)	Pb1^xviii—O1—V	129.5 (3)
O3^vi—Pb1—O3^viii	117.04 (19)	Pb1^xix—O2—V	101.4 (2)
O3^vii—Pb1—O3^viii	117.0 (2)	Pb2^xx—O2—V	129.0 (5)
Cl—Pb2—O3	69.51 (14)	Pb1^vi—O2—V	101.4 (2)
Cl—Pb2—Cl^ix	71.04 (1)	Pb1^xix—O2—Pb2^xx	114.8 (2)
Cl—Pb2—O2^x	139.71 (11)	Pb1^xix—O2—Pb1^vi	86.7 (2)
Cl—Pb2—O3^xi	136.11 (17)	Pb1^vi—O2—Pb2^xx	114.8 (2)
Cl—Pb2—O3^xii	71.01 (16)	Pb2—O3—V	96.1 (2)
Cl—Pb2—O3^xiii	104.06 (14)	Pb2—O3—Pb2ⁱ	117.6 (2)
Cl^ix—Pb2—O3	104.06 (14)	Pb1^vi—O3—Pb2	98.9 (2)
O2^x—Pb2—O3	76.3 (3)	Pb2ⁱ—O3—V	137.5 (3)
O3—Pb2—O3^xi	141.74 (19)	Pb1^vi—O3—V	92.8 (3)
O3—Pb2—O3^xii	82.31 (18)	Pb1^vi—O3—Pb2ⁱ	105.68 (17)
O3—Pb2—O3^xiii	61.38 (14)

Cl—Pb2—O3—V	122.5 (3)	O3—V—O1—Pb1	−51.7 (6)
O3^xi—Pb2—O3—V	−17.7 (5)	O1—V—O3—Pb2	−126.6 (3)
O3^xii—Pb2—O3—V	−164.9 (3)	O2—V—O3—Pb2	110.5 (3)
O3^xiii—Pb2—O3—V	2.6 (2)	O3^xiii—V—O3—Pb2	−3.7 (4)
O3—Pb2—O3^xiii—V	−2.6 (2)	O3—V—O3^xiii—Pb2	3.7 (4)
O2—V—O1—Pb1	68.5 (4)

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

Acknowledgements

We thank the two anonymous reviewers and the Co-editor, A. F. Craievich, for useful comments that helped to improve this manuscript. R. Marr is thanked for his help with the electron probe. The HRPXRD data were collected at the X-ray Operations and Research beamline 11-BM, Advanced Photon Source, Argonne National Laboratory, USA. Use of the Advanced Photon Source was supported by the US Department. of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

Funding information

Funding for this research was provided by: Natural Sciences and Engineering Research Council of Canada (grant to SMA).

References

Akao, A., Aoki, H., Innami, Y., Minamikata, S. & Yamada, T. (1989). Rep. Inst. Med. Dent. Eng. Tokyo Med. Dent. Univ. 23, 25–29. Google Scholar
Ali, R., Yashima, M., Matsushita, Y., Yoshioka, H. & Izumi, F. (2009). J. Solid State Chem. 182, 2846–2851. Web of Science CrossRef ICSD CAS Google Scholar
Antao, S. M. (2012). Am. Mineral. 97, 661–665. CrossRef Google Scholar
Antao, S. M. & Dhaliwal, I. (2017). Minerals, 7, 136. Web of Science CrossRef Google Scholar
Antao, S. M., Duane, M. J. & Hassan, I. (2002). Can. Mineral. 40, 1403–1409. Web of Science CrossRef CAS Google Scholar
Antao, S. M. & Hassan, I. (2002). Can. Mineral. 40, 163–172. Web of Science CrossRef CAS Google Scholar
Antao, S. M. & Hassan, I. (2009). Can. Mineral. 47, 1245–1255. Web of Science CrossRef CAS Google Scholar
Antao, S. M., Hassan, I., Wang, J., Lee, P. L. & Toby, B. H. (2008). Can. Mineral. 46, 1501–1509. Web of Science CrossRef ICSD CAS Google Scholar
Beck, H. P., Douiheche, M., Haberkorn, R. & Kohlmann, H. (2006). Solid State Sci. 8, 64–70. Web of Science CrossRef ICSD CAS Google Scholar
Caglioti, G., Paoletti, A. & Ricci, F. P. (1958). Nucl. Instrum. 3, 223–228. CrossRef CAS Web of Science Google Scholar
Calos, N. J., Kennard, C. H. L. & Davis, R. L. (1990). Z. Kristallogr. 191, 125–129. CrossRef Google Scholar
Cotter-Howells, J. D. & Caporn, S. (1996). Appl. Geochem. 11, 335–342. CAS Google Scholar
Cotter-Howells, J. D., Champness, P. E., Charnocky, J. M. & Pattrick, R. A. D. (1994). Eur. J. Soil Sci. 45, 393–402. CAS Google Scholar
Dai, Y. & Hughes, J. M. (1989). Can. Mineral. 27, 189–192. CAS Google Scholar
Dai, Y., Hughes, J. M. & Moore, P. B. (1991). Can. Mineral. 29, 369–376. CAS Google Scholar
Đordević, T., Šutović, S., Stojanović, J. & Karanović, Lj. (2008). Acta Cryst. C64, i82–i86. Web of Science CrossRef IUCr Journals Google Scholar
Ehm, L., Antao, S. M., Chen, J. H., Locke, D. R., Marc Michel, F., David Martin, C., Yu, T., Parise, J. B., Antao, S. M., Lee, P. L., Chupas, P. J., Shastri, S. D. & Guo, Q. (2007). Powder Diffr. 22, 108–112. Web of Science CrossRef CAS Google Scholar
Elliott, J. C., Wilson, R. M. & Dowker, S. E. P. (2002). Adv. X-ray Anal. 45, 172–181. CAS Google Scholar
Fergus, J. W. (2006). J. Power Sources, 162, 30–40. Web of Science CrossRef CAS Google Scholar
Flis, J., Borkiewicz, O., Bajda, T., Manecki, M. & Klasa, J. (2010). J. Synchrotron Rad. 17, 207–214. Web of Science CrossRef ICSD CAS IUCr Journals Google Scholar
Hashimoto, H. & Matsumoto, T. (1998). Z. Kristallogr. 213, 585–590. Web of Science CrossRef CAS Google Scholar
Hata, M., Marumo, F., Iwai, S. & Aoki, H. (1979). Acta Cryst. B35, 2382–2384. CrossRef CAS IUCr Journals Web of Science Google Scholar
Hendricks, S. B., Jefferson, M. E. & Mosley, V. M. (1932). Z. Kristallogr. 81, 352–369. Google Scholar
Hopwood, J. D., Derrick, G. R., Brown, D. R., Newman, C. D., Haley, J., Kershaw, R. & Collinge, M. (2016). J. Chem. 2016, 9074062. CrossRef Google Scholar
Hughes, J. M., Cameron, M. & Crowley, K. D. (1989). Am. Mineral. 74, 870–876. CAS Google Scholar
Kampf, A. R., Steele, I. M. & Jenkins, R. A. (2006). Am. Mineral. 91, 1909–1917. Web of Science CrossRef ICSD CAS Google Scholar
Laperche, V., Logan, T. J., Gaddam, P. & Traina, S. J. (1997). Environ. Sci. Technol. 31, 2745–2753. CrossRef CAS Web of Science Google Scholar
Larson, A. C. & Von Dreele, R. B. (2000). General Structure Analysis System (GSAS). Report LAUR 86–748. Los Alamos National Laboratory, New Mexico, USA. Google Scholar
Laufek, F., Skála, R., Haloda, J. & Cisařová, I. (2006). J. Czech. Geol. Soc. 51, 271–275. Google Scholar
Lee, P. L., Shu, D., Ramanathan, M., Preissner, C., Wang, J., Beno, M. A., Von Dreele, R. B., Ribaud, L., Kurtz, C., Antao, S. M., Jiao, X. & Toby, B. H. (2008). J. Synchrotron Rad. 15, 427–432. Web of Science CrossRef CAS IUCr Journals Google Scholar
McConnell, D. (1973). Apatite: Its Crystal Chemistry, Mineralogy, Utilization, and Geologic and Biologic Occurrences. New York: Springer-Verlag. Google Scholar
Mehmel, M. (1930). Z. Kristallogr. 75, 323–331. CAS Google Scholar
Mills, S. J., Ferraris, G., Kampf, A. R. & Favreau, G. (2012). Am. Mineral. 97, 415–418. CrossRef Google Scholar
Nakayama, S., Kageyama, T., Aono, H. & Sadaoka, Y. (1995). J. Mater. Chem. 5, 1801–1805. CrossRef CAS Web of Science Google Scholar
Nakayama, S., Sakamoto, M., Higuchi, M., Kodaira, K., Sato, M., Kakita, S., Suzuki, T. & Itoh, K. (1999). J. Eur. Ceram. Soc. 19, 507–510. Web of Science CrossRef CAS Google Scholar
Náray-Szabó, S. (1930). Z. Kristallogr. 75, 387–398. Google Scholar
Okudera, H. (2013). Am. Mineral. 98, 1573–1579. Web of Science CrossRef ICSD CAS Google Scholar
Pasero, M., Kampf, A. R., Ferraris, C., Pekov, I. V., Rakovan, J. & White, T. J. (2010). Eur. J. Mineral. 22, 163–179. Web of Science CrossRef CAS Google Scholar
Rietveld, H. M. (1969). J. Appl. Cryst. 2, 65–71. CrossRef CAS IUCr Journals Web of Science Google Scholar
Robeznieks, A. (2015). Mod. Healthc. 45, 9. Google Scholar
Rouse, R. C., Dunn, P. J. & Peacor, D. R. (1984). Am. Mineral. 69, 920–927. CAS Google Scholar
Sejkora, J., Plášil, J., Císařová, I., Škoda, R., Hloušek, J., Veselovský, F. & Jebavá, I. (2011). J. Geosci. 56, 257–271. Google Scholar
Shannon, R. D. (1976). Acta Cryst. 32, 751–767. CrossRef CAS IUCr Journals Web of Science Google Scholar
Skinner, L. B., Benmore, C. J., Antao, S. M., Soignard, E., Amin, S. A., Bychkov, E., Rissi, E., Parise, J. B. & Yarger, J. L. (2012). J. Phys. Chem. C, 116, 2212–2217. Web of Science CrossRef CAS Google Scholar
Thompson, P., Cox, D. E. & Hastings, J. B. (1987). J. Appl. Cryst. 20, 79–83. CrossRef ICSD CAS Web of Science IUCr Journals Google Scholar
Toby, B. H. (2001). J. Appl. Cryst. 34, 210–213. Web of Science CrossRef CAS IUCr Journals Google Scholar
Trotter, J. & Barnes, W. H. (1958). Can. Mineral. 6, 161–173. CAS Google Scholar
Wang, J., Toby, B. H., Lee, P. L., Ribaud, L., Antao, S. M., Kurtz, C., Ramanathan, M., Von Dreele, R. B. & Beno, M. A. (2008). Rev. Sci. Instrum. 79, 085105. Web of Science CrossRef PubMed Google Scholar
White, T. J. & ZhiLi, D. (2003). Acta Cryst. B59, 1–16. Web of Science CrossRef CAS IUCr Journals Google Scholar

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Volume 25| Part 1| January 2018| Pages 214-221

https://doi.org/10.1107/S1600577517014217

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