DJURLEITE, DIGENITE, AND CHALCOCITE - INTERGROWTHS AND TRANSFORMATIONS

Pósfai, Mihály and Buseck, Peter R. (1994) DJURLEITE, DIGENITE, AND CHALCOCITE - INTERGROWTHS AND TRANSFORMATIONS. American Mineralogist, 79 (3-4). pp. 308-315. ISSN 0003-004X

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Abstract

Intergrowths between djurleite (approximately Cu1.94S) and digenite (approximately Cu1.8S) and between djurleite and chalcocite (Cu2S) and the transformation between djurleite (dj) and chalcocite (cc) were studied using high-resolution transmission electron microscopy. Pseudohexagonal twins are common in djurleite; crystal blocks are rotated relative to each other around [100], the normal of the close-packed layers, by multiples of 60-degrees. Djurleite and digenite (dg) bands are intergrown, with (111)dg parallel to (100)dj, thereby creating a cubic-hexagonal alternation in the sequence of close-packed layers. The typical orientational relationship between coexisting djurleite and chalcocite is where [001]cc is parallel to [100]dj and [010]cc is parallel to one of the [010] or [012] directions of djurleite. If both djurleite and chalcocite occur in a sample, chalcocite easily converts to djurleite under the electron beam through the rearrangement of Cu atoms. A similar electrochemical transformation probably takes place in Cu2S-CdS solar cells and is the reason for the instability of chalcocite in such devices.

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