Clinochalcomenite
Chemical formula: Cu²⁺Se⁴⁺O₃(H₂O)₂
Clinochalcomenite is a very rare copper selenite, forming microscopic, prismatic crystals of an intensely blue-green color.
Properties
- Mohs hardness
- 2
- Color
- bluish green
- Luster
- Vitreous
- Streak
- pale green
- Density
- 0
- Cleavage
- Perfect on {110}
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Clinochalcomenite is identified by its characteristic, intense blue-green color, the form of small, prismatic or acicular crystals forming radial aggregates, and its specific occurrence environment – oxidation zones of selenium and copper deposits. ## Differentiation from Similar Minerals It can be confused with other secondary copper minerals of similar color, such as chalcomenite, brochantite, or malachite. It is distinguished from chalcomenite (orthorhombic system) by its monoclinic crystal system, which can only be determined using advanced research methods. A selenium presence test distinguishes it from other minerals. ## Crystal Forms It forms elongated, prismatic crystals, often terminated by flat faces. These crystals typically group into radial, stellate, or zonally arranged aggregates. It also occurs as fibrous masses and granular coatings.
Geological environment
## Genesis Clinochalcomenite is a secondary mineral formed in the oxidation (weathering) zones of ore deposits containing selenium and copper. It forms under dry and arid conditions as a result of the reaction of oxygen-rich waters with primary copper selenides. ## Mineral Associations It most commonly co-occurs with chalcomenite, as well as with other selenites and selenides, such as ahlfeldite, umangite, and clausthalite. It is also accompanied by other secondary minerals, e.g., malachite, and gangue minerals like quartz or barite. ## Localities The most important localities for this very rare mineral are in Argentina (El Cóndor mine, La Rioja Province - type locality), Bolivia (El Dragón mine), Democratic Republic of Congo (Katanga Province), and the USA (Grand Canyon National Park, Arizona).
Rarity
Very rare
For collectors
## Quality Criteria The most highly valued clinochalcomenite specimens are those with well-formed, sharp crystals of intense, vivid color, forming aesthetic, radial aggregates on a contrasting matrix. Due to their microscopic size, the quality of the crystal or crystal group itself is crucial, rather than the size of the entire specimen. Purity and lack of damage are extremely important. ## Popular Localities Specimens from the El Cóndor mine in Argentina and the El Dragón mine in Bolivia are considered the best in the world. They provide sharp, well-formed microcrystals that serve as a benchmark for this species.
Care and storage
## Cleaning Clinochalcomenite specimens are extremely delicate and sensitive. Mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. Contact with water, which can damage or dissolve the mineral, should be avoided. ## What to Avoid Contact with water, acids, detergents, and all chemicals must be strictly avoided. The mineral is very soft, susceptible to scratches and mechanical damage. It should be protected from high temperatures and sudden temperature changes. ## Storage Clinochalcomenite specimens, typically in the form of micromounts, should be stored exclusively in sealed, lockable "micromount boxes" that protect them from dust, moisture, and physical damage. Exposure to direct sunlight should be avoided.