tennantite-(cu)

TSNB345

Species

Tennantite-(Cu): A partial replacement of enargite by tennantite-(Cu) (EDS verified), with undetermined copper secondary minerals on the surface of the pseudomorph. 60 mm specimen. M. Southwood Collection MS2016.019.
Tennantite-(Cu): A partial replacement of enargite by tennantite-(Cu) (EDS verified), with undetermined copper secondary minerals on the surface of the pseudomorph. 60 mm specimen. M. Southwood Collection MS2016.019.
Image Credit: Malcolm Southwood

Title

tennantite-(cu)

Composition

Cu6(Cu4Cu2)As4S13

Crystal System

Cubic

Status at Tsumeb

Believed valid

Abundance

Very rare

Distribution

First (?) and second (?) oxidation zones.

Paragenesis

Supergene (?)

Type Locality

No

Entry Type

Species TSNB345

General Notes

Following the reclassification and revised nomenclature rules for minerals of the tetrahedrite group (Biagioni et al. 2020a), tennantite-(Cu), IMA2020-096, was approved as a newly defined member of the tennantite sub-group (Biagioni et al. 2020b).

Tennantite-(Cu) has not been formally reported from Tsumeb. However, quantitative WDS analysis of tennantite pseudomorphous after enargite from a specimen in the Southwood collection (catalogue number MS2016.019) gave the following mean composition for the species-defining elements, which is strongly indicative of tennantite-(Cu):

As 17.63 wt %; Sb 0.14; Cd 2.42; Cu 49.33; Fe 0.02; Zn 2.82; S 27.66 (mean of 32 analyses across five grains; M. Števko and M. Southwood, unpublished data; https://www.mindat.org/locentry-1452199.html; accessed October 2024).

Further work is needed to confirm the presence of tennantite-(Cu) at Tsumeb and to assess its abundance and distribution, but it is believed that at least some of the replacements after enargite, found in both the first and second oxidation zones and possibly of supergene origin, are tennantite-(Cu).

Associated Minerals

brochantite (?); chalcocite; devilline (?); enargite; posnjakite (?); sphalerite

Pseudomorphs

Tennantite-(Cu) is reported to form pseudomorphs after the following minerals: enargite