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Formula: Ag4TeS
Sulphide, acanthite group,
silver- and tellurium-
bearing mineral
Crystal System: Monoclinic
Specific gravity: 8.52 calculated
Hardness: 2
Colour: Dark grey, black
Optical properties: Photosensitive
Environments
Volcanic igneous environments
Hydrothermal environments
Localities
At Um Samiuki, Red Sea Governorate, Egypt, a cervelleite-like mineral has been recorded in the
Precambrian (prior to 543 million years ago) silver-rich volcanogenic
zinc - copper -
lead deposits. The associated
hypogene minerals comprise
sphalerite, pyrite,
chalcopyrite, galena,
bornite,
tetrahedrite-tennantite,
hessite and electrum, whereas the
supergene minerals comprise
covellite and mckinstryite.
The cervelleite-like mineral has been observed in two textural positions:
(a) as small (15-40 pm) subhedral crystals close to margins of hessite and
galena grains
(b) as inclusions in sphalerite, where it is associated with
silver-rich bornite,
chalcopyrite and hessite.
The mode of occurrence of the cervelleite-like mineral suggests a
hypogene origin.
(CM 37.143-154).
At the type locality, the Bambollita Mine, Moctezuma, Moctezuma Municipality, Sonora, Mexico, cervelleite
occurs as thin, 30 µm rims surrounding acanthite in
hessite and as vermiform (worm-like) inclusions in the latter.
Cervelleite, acanthite and
hessite are altered rapidly and profoundly by light, in a surface
reaction interpreted as photo-chemical in origin
(EJM 1.3.371-380).
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