Tennantite-(Cd), Cu₆(Cu₄Cd₂)As₄S₁₃, from the Berenguela mining district, Bolivia: the first Cd-member of the tetrahedrite group

Abstract

Tennantite-(Cd), Cu10Cd2As4S13, was approved as a new mineral species from the Berenguela mining district, Pacajes Province, La Paz, Bolivia. It occurs as black metallic anhedral grains, up to 1 mm across, associated with baryte, montmorillonite, and secondary Cd-sulfates (aldridgeite, niedermayrite, and voudourisite). In reflected light, tennantite-(Cd) is isotropic, grey with brownish tints. Reflectance data for the four COM wavelengths in air are [λ (nm):

Tennantite-(Ni), Cu6(Cu4Ni2)As4S13, from Luobusa ophiolite, Tibet, China: a new Ni member of the tetrahedrite group

“…Several cycles of isotropic refinement converged to R 1 = 0.1021, confirming the correctness of the structural model. The M(2) site, which had a rather high U eq value, was split into two position, M(2A) and M(2B) separated by 1.22(2) Å, in agreement with previous studies (Andreasen et al, 2008;Makovicky et al, 2005;Welch et al, 2018;Biagioni et al, 2021Biagioni et al, , 2022aBiagioni et al, , 2022b. Further anisotropic refinement with free site-occupancy factors gave 0.687(12) and 0.157(6) for M(2A) and M(2B) of the 12e and 24g positions, respectively.…”

“…Compared to other species belonging to the tetrahedrite group, the M(2) site of tennantite and zvěstovite-series minerals (As-dominant at the X(3) site) need to be split into two sub-positions, one M(2A) and two neighbouring M(2B), due to the moderately significant high anisotropic thermal motion at the M(2) site (e.g. Wuensch et al, 1966;Makovicky et al, 2005;Sejkora et al, 2021;Biagioni et al, 2021Biagioni et al, , 2022aBiagioni et al, , 2022b.…”

“…The divalent C constituent at the M (1) site plays the role of a valency-imposed double site-occupancy with the monovalent B constituent in keeping the formula charge balance. Tennantite-(Ni) is the first Ni-dominant species in the tennantite series, other members of this series include tennantite-(Fe) (W. Phillips, 1819; R. Phillips, 1819), tennantite-(Zn) (Des Cloizeaux, 1855; Wuensch et al , 1966), tennantite-(Hg) (Biagioni et al , 2021), tennantite-(Cu) (Biagioni et al , 2022a) and tennantite-(Cd) (Biagioni et al , 2022b). The new species was found in the Luobusa chromite deposit, Qusum County, Tibet, China.…”

“…M(2A) = Cu 0.690(12) ; M(2B) = Cu 0.155(6) ; M(1) = Cu 0.76 Ni 0.16 Fe 0.08 ; X(3) = As 0.735 Sb 0.265 reported tennantite species, e.g. 1.08 Å and Å of Cu-rich unsubstituted tennantite(Makovicky et al, 2005); 0.84 Å and 1.68 Å of tennantite-(Cd)(Biagioni et al, 2022b). Clusters of three close M(2B) atoms form a regular triangle with edges of 1.93(5) Å.…”

Argentotetrahedrite-(Cd), Ag6(Cu4Cd2)Sb4S13, a new member of the tetrahedrite group from Rudno nad Hronom, Slovakia.

“…The first Cd-member of the tetrahedrite group – tennantite-(Cd) was described recently by Biagioni et al . (2022). Tetrahedrite-group minerals having chemical compositions corresponding to that of argentotetrahedrite-(Cd) have been reported previously.…”