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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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