Glaukosphaerite: A new nickel analogue of rosasite

Abstract

SummaryGlaukosphaerite, a new secondary basic copper-nickel carbonate was first determined and described from Widgiemooltha (31° 30′ S., 121° 34′ E.), Western Australia, by R. C. Morris at the W.A. Government Chemical Laboratories in 1967. The mineral has since been found at the nickel mines at Kambalda, Windarra, Scotia, Carr Boyd Rocks, and St. Ives, Western Australia, and is apparently an indicator of copper-nickel sulphide mineralization. The name is derived from the colour and spherulitic formation. Associated minerals are goethite, secondary quartz, paratacamite, gypsum, nickeloan varieties of magnesite and malachite, and clays. Glaukosphaerite also fills joints in fresh basic rocks.The type material is from Hampton East Location 48, 3 km N. of the Durkin Shaft, Kambalda. Glaukosphaerite is monoclinic, a 9·34 Å, b 11·93 Å, c 3·07 Å, β 90–1°, space group indeterminate, c axis disordered, six strongest X-ray powder lines are 2·587 (10b) 201, 3·68(7b) 220, 2·516(4) 240, 211, 5·04(3) 120, 2·124(3b), 1·473(3). The mineral occurs in green spherules of fibres cleaved and elongated along c, D = 3·78 to 3·96 increasing with Cu, is brittle, H. 3 to 4, and has dull to subvitreous to silky lustre.α 1·69–1·71 green, β ≈ γ 1·83–1·85 yellow-green, α:[001] 7°.Chemical analysis on the type material, D 3·78, containing 0·5 % goethite impurity and minimal inseparable malachite, gave CuO 41·57, NiO 25·22, CoO 0·07, ZnO 0·02, Fe2O3 0·47, MgO 1·23, SiO2 < 0·01, CO2 21·70, H2O+ 9·85, H2O− < 0·01, sum 100·13%. After deduction of goethite the unit cell contains 4[(Cu,Ni,Mg,Co)1.74C0·96H2·12O4·73]. This unit-cell content is deficient in metal ions and oxygen and contains excess H, when compared to 4[(Cu,Ni)2(OH)2CO3]. Two analyses of malachite-bearing glaukosphaerite from Widgiemooltha and Carr Boyd Rocks show the same deficiencies and excess not previously recorded in malachite, rosasite, or aurichalcite analyses. Glaukosphaerite, 4[(Cu,Ni)2(OH)2CO3] is the nickel analogue of rosasite 4[(Cu,Zn)2(OH)2CO3].From results based on X-ray rotation patterns of oriented rosasite fibres from Sardinia and Durango with supplementary electron-microprobe studies and Guinier powder-film data, the authors consider glaukosphaerite and rosasite to be separate mineral species from the related malachite, 4[Cu2(OH)2CO3].Type material is preserved in the government collection at the Government Chemical Laboratories, Perth, Western Australia.