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Description and crystal structure of a new mineral, edwardsite, Cu (sub 3) Cd (sub 2) (SO (sub 4) ) (sub 2) (OH) (sub 6) .4H (sub 2) O, from Broken Hill, New South Wales, Australia

P. Elliott, J. Brugger and T. Caradoc-Davies
Description and crystal structure of a new mineral, edwardsite, Cu (sub 3) Cd (sub 2) (SO (sub 4) ) (sub 2) (OH) (sub 6) .4H (sub 2) O, from Broken Hill, New South Wales, Australia
Mineralogical Magazine (February 2010) 74 (1): 39-53

Abstract

Edwardsite, Cu (sub 3) Cd (sub 2) (SO (sub 4) ) (sub 2) (OH) (sub 6) .4H (sub 2) O, is a new mineral from the Block 14 Opencut, Broken Hill, New South Wales, Australia. It occurs as druses of tabular and bladed crystals up to 0.06 mm in size, associated with niedermayrite and christelite. Edwardsite is pale blue, transparent with vitreous lustre and has excellent cleavage parallel to {100}. Density was not measured but the calculated density, from the empirical formula, is 3.53 g cm (super -3) and the Mohs hardness is approximately 3. Optically, it is biaxial negative with alpha approximately 1.74, beta =1.762(4), gamma approximately 1.77 and 2V (sub calc.) approximately +62 degrees . The optical orientation is X=b, Y approximately a, Z approximately c. Electron microprobe analysis gave (wt.%): CdO 32.43, CuO 28.06, ZnO 2.26, FeO 0.08, SO (sub 3) 20.35, H (sub 2) O (sub calc.) (from crystal-structure analysis) 14.14, totalling 99.32. The empirical formula, calculated on the basis of 18 oxygen atoms is Cu (sub 2.77) Cd (sub 1.98) Zn (sub 0.22) Fe (sub 0.01) (SO (sub 4) ) (sub 2.00) (OH) (sub 5.95) .4.06H (sub 2) O. Edwardsite is monoclinic, space group P2 (sub 1) /c, with a=10.863(2) Aa, b=13.129(3) Aa, c=11.169(2) Aa, beta =113.04(3) degrees , V=1465.9(5) Aa (super 3) (single-crystal data) and Z=4. The eight strongest lines in the powder diffraction pattern are [d (Aa), (I/I (sub 0) ), (hkl)]: 9.991, (90), (100); 5.001, (90), (200, 211; 4.591, (45), (202); 3.332, (60), (300, 032); 3.005, (30), (023); 2.824, (40), (142); 2.769, (55), (204, 042, 104); 2.670, (45), (242). The crystal structure was determined by direct methods and refined to R1=3.21% using 1904 observed reflections with F (sub o) >4sigma (F (sub o) ) collected using synchrotron X-ray radiation (lambda = 0.773418 Aa). The structure is based on infinite sheets of edge-sharing Cuphi (sub 6) (phi : O (super 2-) , OH) octahedra and Cdphi (sub 7) (phi : O (super 2-) , H (sub 2) O) polyhedra parallel to (100). The sheets are decorated on both sides by corner-sharing (SO (sub 4) ) tetrahedra, which also corner-link to isolated Cdphi (sub 6) octahedra, thus connecting adjacent sheets. Moderate-strong to weak hydrogen bonding provides additional linkage between sheets.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 74
Serial Issue: 1
Title: Description and crystal structure of a new mineral, edwardsite, Cu (sub 3) Cd (sub 2) (SO (sub 4) ) (sub 2) (OH) (sub 6) .4H (sub 2) O, from Broken Hill, New South Wales, Australia
Affiliation: University of Adelaide, School of Earth and Environmental Sciences, Adelaide, South Aust., Australia
Pages: 39-53
Published: 201002
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 50
Accession Number: 2010-050890
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
S37°30'00" - S28°15'00", E141°00'00" - E153°30'00"
Secondary Affiliation: South Australian Museum, AUS, AustraliaAustralian Synchrotron, AUS, Australia
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201028
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