1910–1911
Britannica 11th
Encyclopaedia Britannica · 11th edition
ERUBESCITE, a native copper-iron sulphide, Cu4FeS4, of importance as an ore of copper. It crystallizes in the cubic system, the usual form being that of interpenetrating cubes twinned on an octahedral plane. The faces are usually curved and rough, and the crystals confusedly aggregated together. Compact and granular masses are of more frequent occurrence. The colour on a freshly fractured surface is bronzy or coppery, but in moist air this rapidly tarnishes with iridescent blue and red colours; hence the names purp…
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- Vol. 9, pp. 757-757