GASPÉITE AND ASSOCIATED Ni-RICH MINERALS FROM VEINS IN ALTERED ULTRABASIC ROCKS FROM DUBOŠTICA, BOSNIA AND HERZEGOVINA
A suite of nickel minerals, gaspeite, retgersite and nickelhexahydrite, was found in veins of altered ultramafic rocks from Dubostica, Bosnia and Hercegovina, in material deposited in the National Museum in Sarajevo. Unit-cell dimensions and volumes of the minerals are: gaspeite: a 4.648(3), c 14.95(2) A (rhombohedral cell a 5.660 A, α 48.49°), V 279.7 A 3 ; retgersite: a 6.787(5), c 18.27(2) A, V 842(1) A 3 ; nickelhexahydrite: a 9.925(7), b 7.232(7), c 24.16(2), β 98.55(7)°, V 1715(2) A 3 . The chemical composition of the gaspeite from Dubostica, obtained by ICP–AES analysis, is: NiO 49.63, MgO 0.17, CaO 0.45, FeO 6.36, CO 2 43.25, total 99.87 wt%. This gives the empirical formula (based on three atoms of oxygen) (Ni 0.73 Fe 0.10 Ca 0.01 ) ∑0.84 C 1.08 O 3.00 . The association of gaspeite, retgersite and nickelhexahydrite has formed as a result of reactions involving a series of kinetically controlled transitory equilibria, and is characteristic of near-surface hydrothermal alteration.