Nukundamite, a New Mineral, and Idaite

C. M. Rice, A. J. Criddle, D. Atkin and J. F. W. Bowles
Department of Geology and Mineralogy, The University, Aberdeen AB9 1AS
Department of Mineralogy, British Museum (Natural History), Cromwell Road, London SW7 5BD
Geochemical Division, Institute of Geological Sciences, 64/78 Gray's Inn Road, London WC1X 8NG

Summary: A new mineral, nukundamite, from a Fijian kuroko deposit is described. It has been referred to as idaite, Cu5FeS6, or Cu5.5xFexS6.5x. Electron-probe analyses gave Cu 56.51, Fe 9.64, and S 33.51, total with traces of Ag and As is 99.79%. Hexagonal with a 3.782, c 11.187 Å, Z = 1. Empirical formula Cu3.37, Fe0.66, S3.97 on the basis of eight atoms. Copper-coloured, metallic lustre, cleavage {0001} perfect. Density (g cm−3) 4.53 (calc), 4.30 (meas). Strongly pleochroic from reddish orange (Ro) to pale grey (Re). Parallel extinction. Very strong anisotropy with pale green-grey rotation colours. Reflectance values and quantitative colour values in air and oil are given. Similarities with the covelline structure are indicated.

An attempt to fully describe idaite from the Ida mine was unsuccessful. The description of the type material therefore remains inadequate.

Mineralogical Magazine; June 1979 v. 43; no. 326; p. 193-200; DOI: 10.1180/minmag.1979.043.326.01
© 1979, The Mineralogical Society
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