Moolooite, a naturally occurring hydrated copper oxalate from Western Australia

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Authors:Clarke, R. M.; Williams, I. R.
Author Affiliations:Primary:
Gov. Chem. Lab., Perth, West. Aust., Australia
Other:
Geol. Surv. West. Aust., Australia
Volume Title:Mineralogical Magazine
Source:Mineralogical Magazine, 50 Part 2(356), p.295-298. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X
Publication Date:1986
Note:In English. 7 refs.; illus. incl. 1 table
Summary:Moolooite, a naturally occurring hydrated copper oxalate has been identified in a sulphide-bearing quartz outcrop 12 km east of Mooloo Downs station homestead (25° 01' 30" S., 116° 06' 30" E.), Western Australia. It has apparently formed by the interaction of solutions derived from bird guano and weathering copper sulphides. Partial microchemical analysis indicates a composition corresponding to CuC2O4 · 0.44H2O. The infra-red spectrum is similar to that of the artificial compound with diagnostic absorption bands at 3490, 2975, 2935, 1980, 1940, 1660, 1365,1320, 830, 510, 390, and 315 cm-1. Powder X-ray diffraction patterns indicate a disordered structure with orthorhombic symmetry; a 5.35, b 5.63, c 2.56 Å, Z = 1. The strongest lines of the powder pattern are [d Å, I, hkl]: 3.88, 100, (110); 2.50, 30, (120); 2.33, 18, (011); 2.31, 25,(101); 2.14, 20, (111); 1.938, 18, (220); 1.787, 25, (121); 1.753, 30, (211); 1.216, 15, (112). Unindexed very weak diffuse lines on some patterns can be indexed assuming a supercell with a' = a, b' = 2b, c' = 2c indicating the presence of ordered crystallites. Moolooite occurs as micro-concretionary crusts and powder in cracks and solution cavities resulting from sulphide oxidation. It is found associated with opaline silica, gypsum, broehantite, antlerite, atacamite, whewellite, sampleite, and libethenite. It is turquoise-green in colour with similar streak, lustre dull to waxy, calculated density 3.43 g/cm3. Moolooite is composed of aggregates of generally sub-micrometre sized equidimensional crystallites with α ∼ 1.57 and γ ∼ 1.95. By analogy with artificial copper oxalate, moolooite is constructed from infinite ribbon-like elementary structural units consisting of alternating Cu2+ and (C2O4)2- ions. These units are arranged en echelon in layers which are stacked with displacements so that octahedral coordination of copper ions is completed by oxygen atoms in adjacent layers. The minimal role played by water in the structure and composition of moolooite distinguish it from other oxalate minerals. Because of the zeolitic character of the water a general formula CuC2O4 · nH2O (0 ≤ n ≤ 1) appears to be appropriate. [R.A.H.]
Subjects:Chemical composition; Crystal structure; Infrared spectra; Mineral data; Mineralogy; Minerals; Optical properties; Oxides; Physical properties; Spectra; X-ray data; Australasia; Australia; Western Australia; Bunbury Well; Copper oxalate hydrate; Moolooite
Coordinates:S250130 S250130 E1160630 E1160630
Abstract Numbers:86M/4986
Record ID:1986086939
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland
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