Cerromojonite
Chemical formula: Cu<sup>1+</sup>Pb<sup>2+</sup>Bi<sup>3+</sup>Se<sup>2-</sup><sub>3</sub>
Cerromojonite is a rare copper, lead, and bismuth selenide, forming metallic-lustered, platy crystals.
Properties
- Luster
- Metallic
- Streak
- Black
- Density
- 7.81
- Cleavage
- Perfect on {0001}
- Transparency
- Opaque
- Crystal system
- Trigonal
Diagnostic features
## Identification Identification of cerromojonite is possible only through advanced laboratory methods, such as chemical analysis using an electron microprobe (EDS/WDS) and X-ray diffraction (XRD). Visually, under a microscope, its steel-gray color, metallic luster, and characteristic platy crystal habit can be observed. ## Distinguishing from Similar Minerals Cerromojonite is almost impossible to distinguish with the naked eye from other co-occurring, rare selenides, such as watkinsonite, petrovicite, or clausthalite. All these minerals form similar, small, metallic-lustered crystals. Definitive differentiation requires specialized analysis. ## Crystal Forms Cerromojonite crystals have a platy or lamellar habit, often with a hexagonal outline. They usually form small, isolated flakes or small aggregates on the surface of other minerals.
Geological environment
## Genesis Cerromojonite forms under low-temperature hydrothermal conditions. It occurs in calcite veins cutting black shales. It is a product of crystallization from solutions rich in selenium, copper, lead, and bismuth. ## Mineral Associations This mineral co-occurs with other, often very rare selenides. At the type locality, it was found in association with clausthalite, watkinsonite, petrovicite, umangite, klockmannite, berzelianite, eskebornite, chalcomenite, as well as with calcite and hematite. ## Localities The only confirmed occurrence of cerromojonite in the world is its type locality – the El Dragón mine, in Antonio Quijarro Province, Potosí Department, Bolivia.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a cerromojonite specimen primarily depends on the presence of well-formed, sharp, and clearly visible crystals under a microscope. Specimens with isolated crystals set against a contrasting background, such as white calcite, are most highly valued. Crystal size, although always microscopic, is also important – larger flakes are more desirable. Association with other rare selenides is also significant. ## Popular Localities The only source of cerromojonite specimens is the El Dragón mine in Bolivia. Material from this mine is extremely prized by collectors specializing in mineral systematics and microminerals.
Care and storage
## Cleaning Specimens of cerromojonite should generally not be cleaned. Any attempts at mechanical or chemical cleaning can irreversibly damage the microscopic crystals. If dust removal is necessary, a gentle stream of compressed air can be used from a safe distance. ## What to Avoid Avoid contact with chemicals, acids, and detergents. The mineral is potentially susceptible to oxidation, so it should be protected from moisture and sudden temperature changes. It should not be washed in water or cleaned with ultrasonics. ## Storage Cerromojonite specimens, as microminerals, should be stored in specialized "micromount" boxes that protect them from dust, mechanical damage, and moisture. Avoid exposure to direct sunlight.