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Formula: CuPbBiSe3
Valence: Cu1+Pb2+Bi3+Se2-3
Selenide, bournonite group,
bismuth-bearing mineral
Crystal System: Orthorhombic
Specific gravity: 7.035 calculated
Streak: Black
Colour: Black
Luminescence: Not fluorescent under UV
Environments
Sedimentary environments
Hydrothermal environments
Cerromojonite is a relatively new mineral, approved in 2018 and to date (May 2026) reported only from the type locality.
Localities
At the type locality, El Dragón mine, Porco Municipality, Antonio Quijarro Province, Potosí, Bolivia, cerromojonite
occurs either as minute grains (up to 30 µm in size) in interstices of
hansblockite-quijarroite intergrowths,
forming an angular network-like intersertal texture, or as elongated, thin-tabular crystals (up to 200 µm long and 40 µm wide)
within lath-shaped or acicular mineral aggregates (interpreted as pseudomorphs) up to 2 mm in length and 200 µm in width.
Cerromojonite is non-fluorescent, black, and opaque, with a metallic lustre and black streak. It is brittle, with an
irregular fracture, and no obvious cleavage and parting. Lamellar twinning on is common. It is deposited from strongly oxidising
low-temperature hydrothermal fluids, both as a primary and a
secondary phase. It is named for Cerro Mojon, the highest mountain peak
close to the El Dragón mine
(Minerals 8.10.420).
The occurrence is in a vein in a shear zone cutting a series of thinly stratified,
pyrite-rich black shales, and reddish grey,
hematite-bearing siltstones.
Associated minerals include:
Type I: hansblockite, quijarroite,
penroseite, klockmannite,
watkinsonite, clausthalite and
petrovicite
and
Type II: watkinsonite, quijarroite,
clausthalite, unnamed CuNi2Se4 and
klockmannite.
(HOM).
Cerromojonite from El Dragón mine - Image
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