Crystal structure study of a cobaltoan dolomite from Kolwezi, Democratic Republic of Congo

Perchiazzi, N.

doi:10.1107/S2056989015003126

inorganic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 71| Part 3| March 2015| Page i3

doi:10.1107/S2056989015003126

Open

access

Crystal structure study of a cobaltoan dolomite from Kolwezi, Democratic Republic of Congo

Natale Perchiazzi ^a ^*

^aEarth Sciences Department, Pisa University, Via S. Maria 53, I-56126, Pisa, Italy
^*Correspondence e-mail: natale.perchiazzi@unipi.it

Edited by I. D. Brown, McMaster University, Canada (Received 4 February 2015; accepted 13 February 2015; online 21 February 2015)

A structural study has been undertaken on a cobaltoan dolomite, with chemical formula CaMg_0.83Co_0.17(CO₃)₂ (calcium magnesium cobalt dicarbonate), from Kolwezi, Democratic Republic of Congo. Pale-pink euhedral cobaltoan dolomite was associated with kolwezite [(Cu_1.33Co_0.67)(CO₃)(OH)₂] and cobaltoan malachite [(Cu,Co)₂(CO₃)(OH)₂]. A crystal with a Co:Mg ratio of 1:5.6 (SEM/EDAX measurement), twinned on (11 -2 0) was used for crystal structural refinement. The refinement of the structural model of Reeder & Wenk [Am. Mineral. (1983 ), 68, 769–776; Ca at site 3a with site symmetry -3; Mg site at site 3b with site symmetry -3; C at site 6c with site symmetry 3; O at site 18f with site symmetry 1] showed that Co is totally incorporated in the Mg site, with refined occupancy Mg_0.83Co_0.17, which compares with Mg_0.85Co_0.15 from chemical data. The Co substitution reflects in the expansion of the cell volume, with a pronounced increasing of the c cell parameter.

Keywords: crystal structure; dolomite; cobaltoan; Kolwezi.

CCDC reference: 1049359

1. Related literature

For general background, see: Barton et al. (2015 ); Pertlik (1986 ). For isotypic structures, see: Reeder & Wenk (1983). For kolwezite, see: Deliens & Piret (1980 ).

2. Experimental

2.1. Crystal data

CaMg_0.83Co_0.17(CO₃)₂
M_r = 190.38
Trigonal, $[R \overline 3]$
a = 4.8158 (1) Å
c = 16.0488 (6) Å
V = 322.34 (2) Å³
Z = 3
Mo Kα radiation
μ = 2.17 mm⁻¹
T = 295 K
0.20 × 0.15 × 0.12 mm

2.2. Data collection

Bruker SMART Breeze CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ) T_min = 0.621, T_max = 0.746
738 measured reflections
258 independent reflections
257 reflections with I > 2σ(I)
R_int = 0.010

2.3. Refinement

R[F² > 2σ(F²)] = 0.019
wR(F²) = 0.059
S = 0.96
258 reflections
20 parameters
1 restraint
Δρ_max = 0.46 e Å⁻³
Δρ_min = −0.32 e Å⁻³

Table 1
Selected bond lengths (Å)

Ca1—O1ⁱ	2.3833 (10)
(Mg1/Co1)—O1ⁱⁱ	2.0923 (9)
C1—O1	1.2853 (9)
Symmetry codes: (i) $[-x+y+{\script{1\over 3}}, -x+{\script{2\over 3}}, z-{\script{1\over 3}}]$ ; (ii) $[-x+y+{\script{2\over 3}}, -x+{\script{1\over 3}}, z+{\script{1\over 3}}]$ .

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXS2014 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008, 2015 ) and WinGX (Farrugia, 2012 ); molecular graphics: CrystalMaker (CrystalMaker, 2010 ); software used to prepare material for publication: publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1049359

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: 10.1107/S2056989015003126/br2247sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S2056989015003126/br2247Isup2.hkl

checkCIF report

Synthesis and crystallization top

Cobaltoan dolomite was picked from a kolwezite sample from Kolwezi (inventory number RC 3987) kindly provided us by H. Goethals, Royal Belgian Institute for Natural Sciences, Brussels. Pale pink euhedral cobaltoan dolomite was associated with kolwezite and cobaltoan malachite. All these minerals occur in the supergene zones of Cu—Co sulfide ore deposits,originating from the alteration of primary sulphides such as carrollite,Cu(Co,Ni)₂As₄

Refinement top

During the refinement, the twinning according to the (1120) common law was detected and accounted for, with a refined BASF parameter of 0.798. The sum of Co and Mg occupancies in Mg site was constrained to be equal to 1, no other constraint was applied.

Related literature top

For general background, see: Barton et al. (2015); Pertlik (1986). For isostructural/isotypic structures, see: Reeder & Wenk (1983). For kolwezite, see: Deliens & Piret (1980).

Computing details top

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS2014 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008, 2015) and WinGX (Farrugia, 2012); molecular graphics: CrystalMaker (CrystalMaker, 2010); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

	Fig. 1. Micro photograph of the cobaltoan dolomite specimen, where pale pink cobaltoan dolomite is associated with pale green cobaltoan malachite.
	Fig. 2. The crystal structure of cobaltoan dolomite, in a projection along [100], slightly tilted by 5° about along the x Cartesian rotation axis. Ca-centered octahedra are cyan, whereas Mg-centered octahedra are yellow; carbon and oxygen atoms are represented as green and red spheres, respectively.
	Fig. 3. Coordination polyhedra in cobaltoan dolomite. Displacement ellipsoids are drawn at the 50% probability.

Calcium magnesium cobalt dicarbonate top

Crystal data top

CaMg_0.83Co_0.17(CO₃)₂	F(000) = 284
M_r = 190.38	D_x = 2.930 Mg m⁻³
Trigonal, R3	Mo Kα radiation, λ = 0.71073 Å
a = 4.8158 (1) Å	µ = 2.17 mm⁻¹
c = 16.0488 (6) Å	T = 295 K
V = 322.34 (2) Å³	Cleavage rhombohedron, pale pink
Z = 3	0.2 × 0.15 × 0.12 mm

Data collection top

Bruker SMART Breeze CCD diffractometer	257 reflections with I > 2σ(I)
ω scans	R_int = 0.010
Absorption correction: multi-scan (SADABS; Bruker, 2008)	θ_max = 32.4°, θ_min = 3.8°
T_min = 0.621, T_max = 0.746	h = −7→3
258 measured reflections	k = 0→7
738 independent reflections	l = −23→23

Refinement top

Refinement on F²	20 parameters
Least-squares matrix: full	1 restraint
R[F² > 2σ(F²)] = 0.019	w = 1/[σ²(F_o²) + (0.0438P)² + 0.562P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.059	(Δ/σ)_max < 0.001
S = 0.96	Δρ_max = 0.46 e Å⁻³
258 reflections	Δρ_min = −0.32 e Å⁻³

Crystal data top

CaMg_0.83Co_0.17(CO₃)₂	Z = 3
M_r = 190.38	Mo Kα radiation
Trigonal, R3	µ = 2.17 mm⁻¹
a = 4.8158 (1) Å	T = 295 K
c = 16.0488 (6) Å	0.2 × 0.15 × 0.12 mm
V = 322.34 (2) Å³

Data collection top

Bruker SMART Breeze CCD diffractometer	738 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2008)	257 reflections with I > 2σ(I)
T_min = 0.621, T_max = 0.746	R_int = 0.010
258 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.019	20 parameters
wR(F²) = 0.059	1 restraint
S = 0.96	Δρ_max = 0.46 e Å⁻³
258 reflections	Δρ_min = −0.32 e Å⁻³

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. Refined as a 2-component twin.

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
Ca1	0.0000	0.0000	0.0000	0.01249 (17)
Mg1	0.0000	0.0000	0.5000	0.0104 (3)	0.828 (4)
Co1	0.0000	0.0000	0.5000	0.0104 (3)	0.172 (4)
C1	0.0000	0.0000	0.24297 (12)	0.0106 (4)
O1	0.2482 (2)	−0.0341 (2)	0.24403 (6)	0.0143 (2)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Ca1	0.0121 (2)	0.0121 (2)	0.0133 (3)	0.00605 (10)	0.000	0.000
Mg1	0.0091 (3)	0.0091 (3)	0.0130 (4)	0.00456 (15)	0.000	0.000
Co1	0.0091 (3)	0.0091 (3)	0.0130 (4)	0.00456 (15)	0.000	0.000
C1	0.0103 (5)	0.0103 (5)	0.0112 (8)	0.0051 (3)	0.000	0.000
O1	0.0117 (4)	0.0156 (4)	0.0183 (4)	0.0088 (3)	−0.0024 (3)	−0.0033 (3)

Geometric parameters (Å, º) top

Ca1—O1ⁱ	2.3833 (10)	Mg1—O1^ix	2.0923 (9)
Ca1—O1ⁱⁱ	2.3833 (10)	Mg1—O1^x	2.0923 (9)
Ca1—O1ⁱⁱⁱ	2.3833 (10)	Mg1—O1^xi	2.0923 (9)
Ca1—O1^iv	2.3833 (10)	Mg1—O1^xii	2.0923 (9)
Ca1—O1^v	2.3833 (10)	C1—O1	1.2853 (9)
Ca1—O1^vi	2.3833 (10)	C1—O1^xiii	1.2853 (9)
Mg1—O1^vii	2.0923 (9)	C1—O1^xiv	1.2853 (9)
Mg1—O1^viii	2.0923 (9)	C1—Ca1^xv	3.1359 (9)

O1ⁱ—Ca1—O1ⁱⁱ	180.00 (5)	O1^viii—Mg1—O1^ix	91.62 (4)
O1ⁱ—Ca1—O1ⁱⁱⁱ	92.43 (3)	O1^vii—Mg1—O1^x	91.62 (4)
O1ⁱⁱ—Ca1—O1ⁱⁱⁱ	87.57 (3)	O1^viii—Mg1—O1^x	88.38 (4)
O1ⁱ—Ca1—O1^iv	87.57 (3)	O1^ix—Mg1—O1^x	180.0
O1ⁱⁱ—Ca1—O1^iv	92.43 (3)	O1^vii—Mg1—O1^xi	91.62 (4)
O1ⁱⁱⁱ—Ca1—O1^iv	180.00 (4)	O1^viii—Mg1—O1^xi	88.38 (4)
O1ⁱ—Ca1—O1^v	87.57 (3)	O1^ix—Mg1—O1^xi	91.62 (4)
O1ⁱⁱ—Ca1—O1^v	92.43 (3)	O1^x—Mg1—O1^xi	88.38 (4)
O1ⁱⁱⁱ—Ca1—O1^v	92.43 (3)	O1^vii—Mg1—O1^xii	88.38 (4)
O1^iv—Ca1—O1^v	87.57 (3)	O1^viii—Mg1—O1^xii	91.62 (4)
O1ⁱ—Ca1—O1^vi	92.43 (3)	O1^ix—Mg1—O1^xii	88.38 (4)
O1ⁱⁱ—Ca1—O1^vi	87.57 (3)	O1^x—Mg1—O1^xii	91.62 (4)
O1ⁱⁱⁱ—Ca1—O1^vi	87.57 (3)	O1^xi—Mg1—O1^xii	180.00 (4)
O1^iv—Ca1—O1^vi	92.43 (3)	O1—C1—O1^xiii	119.984 (5)
O1^v—Ca1—O1^vi	180.00 (8)	O1—C1—O1^xiv	119.983 (5)
O1^vii—Mg1—O1^viii	180.0	O1^xiii—C1—O1^xiv	119.981 (5)
O1^vii—Mg1—O1^ix	88.38 (4)

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

Selected bond lengths (Å) top

Ca1—O1ⁱ	2.3833 (10)	Mg1—O1^ix	2.0923 (9)
Ca1—O1ⁱⁱ	2.3833 (10)	Mg1—O1^x	2.0923 (9)
Ca1—O1ⁱⁱⁱ	2.3833 (10)	Mg1—O1^xi	2.0923 (9)
Ca1—O1^iv	2.3833 (10)	Mg1—O1^xii	2.0923 (9)
Ca1—O1^v	2.3833 (10)	C1—O1	1.2853 (9)
Ca1—O1^vi	2.3833 (10)	C1—O1^xiii	1.2853 (9)
Mg1—O1^vii	2.0923 (9)	C1—O1^xiv	1.2853 (9)
Mg1—O1^viii	2.0923 (9)

Acknowledgements

Dr H. Goethals, Royal Belgian Institute for Natural Sciences, is kindly acknowledged for providing the mineral sample.

References

Barton, I., Yang, H. & Barton, M. D. (2015). Can. Mineral.. In the press. Google Scholar
Bruker (2008). APEX2, SAINT and SADABS. Bruker AXS Inc. Madison, Wisconsin, USA. Google Scholar
CrystalMaker (2010). CrystalMaker. CrystalMaker Software Ltd, Yarnton, England. Google Scholar
Deliens, M. & Piret, P. (1980). Bull. Mineral. 103, 179–184. CAS Google Scholar
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Web of Science CrossRef CAS IUCr Journals Google Scholar
Pertlik, F. (1986). Acta Cryst. C42, 4–5. CrossRef CAS IUCr Journals Google Scholar
Reeder, R. J. & Wenk, H. R. (1983). Am. Mineral. 68, 769–776. CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 71| Part 3| March 2015| Page i3

doi:10.1107/S2056989015003126

Open

access

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Plain Text

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Plain Text

Search IUCr Journals		doi		Advanced search
Author		volume	page

inorganic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Crystal structure study of a cobaltoan dolomite from Kolwezi, Democratic Republic of Congo

1. Related literature

2. Experimental

2.1. Crystal data

2.2. Data collection

2.3. Refinement

Supporting information

Acknowledgements

References

inorganic compounds