Coupled Substitutions in Goldfieldite-Tetrahedrite Minerals from the Iriki Mine, Japan

Masaaki Shimizu and Chris J. Stanley
University Museum, University of Tokyo, Tokyo 113, Japan
British Museum (Natural History), London SW7 5BD, U.K.

Abstract: Chemical compositions of goldfieldite-tetrahedrite series minerals from the Iriki mine in Japan are reported for the frst time. The compositional variations of coexisting goldfieldite [atomic proportion Te > (Sb + As + Bi)], tellurian tetrahedrite [Sb > (Te + As + Bi)], and Te-free tetrahedrite from this locality are considered alongside data from the literature. These show that the substitution of (Sb, As)3+ for Te4+ in natural goldfieldite-tetrahedrite series minerals occurs by the following two mechanisms: (i) tetrahedrite, Cu10+(Cu,Fe,Zn)22+(Sb,As)43+S13and goldfieldite, Cu12+(Sb,As)23+Te24+S13 form a continuous solid-solution according to the coupled substitution of Cu+Te4+ for (Cu,Fe,Zn)2+(Sb,As)3+, and (ii) goldfieldite, Cu12+(Sb,As)23+Te4+S13 and the ideal end-member,Cu10+Te44+S13 might also form a continuous solid-solution by the coupled substitution of □(vacancy)Te4+ for Cu+(Sb,As)3+. According to this work, the general formulae of tellurian tetrahedrite and goldfieldite are, therefore, respectively, Cu10+x+(Cu,Fe,Zn)2−x2+(Sb,As)4−x3+Tex4+S13, with x = 0 to 2 and Cu12−y+Te2+y4+(Sb,As)2−y3+S13, with y = 0 to 2.

Keywords: goldfieldite-tetrahedrite series • coupled substitutions • Iriki mine, Japan

Mineralogical Magazine; December 1991 v. 55; no. 381; p. 515-519; DOI: 10.1180/minmag.1991.055.381.03
© 1991, The Mineralogical Society
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