Tennantite-(Cd)

tennantite-(Cd)

aldridgeite

niedermayrite

voudourisite

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Formula: Cu6(Cu4Cd2)As4S13
Sulpharsenite, tetrahedrite group, cadmium-bearing mineral
Crystal System: Isometric
Specific gravity: 4.724 calculated
Hardness: 3½ to 4
Streak: Reddish brown
Colour: Black
Environments

Volcanic igneous environments
Sedimentary environments
Hydrothermal environments

Tennantite-(Cd) is a new mineral, approved in 2021 and to date (May 2023) reported only from the type locality.

Localities

The type locality is the Berenguela mining district, José Manuel Pando Province, La Paz, Bolivia. The mining district includes several sediment- and volcanic- hosted veins that were exploited during Spanish colonial times but no mining activity has taken place since the 1940s. The older sedimentary rocks include the red quartz arenites and mudstones and black to red arkoses. The younger volcanic-rich units include interbedded sandstones, conglomerates, reworked tuffaceous sediments and pyroclastic airfall deposits.
The mineral deposits include cadmium-rich veins in the older sedimentary rocks and cadmium-poor veins in the younger volcaniclastic and intrusive rocks. The samples containing tennantite-(Cd) were probably mined in the upper part of the veins in the sedimentary rocks in the first half of the 20th century. Tennantite-(Cd) occurs as anhedral grains, up to 1 × 1 mm in size, black in colour, with a reddish-brown streak, and metallic lustre.
In the holotype specimen, tennantite-(Cd) occurs in baryte, associated with montmorillonite and some secondary sulphates of cadmium such as aldridgeite, niedermayrite and voudourisite (MM 86.834–840).

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