Cuproneyite
Chemical formula: Cu¹⁺₇Pb²⁺₂₇Bi³⁺₂₅S²⁻₆₈
Kupčíkoneite is a rare copper, lead, and bismuth sulfide, forming acicular crystals with a metallic, silvery-gray luster.
Properties
- Mohs hardness
- 3
- Luster
- Metallic
- Density
- 7.113
- Cleavage
- Parallel to the c axis
- Fracture
- Irregular/Uneven
- Transparency
- Opaque
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identifying kupčíkoneite based on visual characteristics is practically impossible and requires advanced analytical methods, such as chemical composition analysis (EDS) using an electron microscope or X-ray diffraction (XRD). In collecting conditions, identification relies on trust in the label and the reputation of the locality. ## Distinguishing from Similar Minerals Kupčíkoneite is macroscopically indistinguishable from many other rare lead and bismuth sulfosalts, such as neyite, cosalite, lillianite, or other minerals from the pavonite group. All of them form similar acicular or fibrous crystals with a metallic luster. Definitive differentiation is possible only through laboratory analysis. ## Crystal Forms Kupčíkoneite crystals are strongly elongated, acicular or hair-like, often flexible. They typically form disordered, tangled, or radial aggregates embedded in the host rock or filling small voids.
Geological environment
## Genesis Kupčíkoneite is a hydrothermal mineral. It forms in ore veins, where it crystallizes from solutions rich in copper, lead, bismuth, and sulfur. Its formation is associated with the final stages of crystallization in polymetallic deposits. ## Mineral Associations At the type locality in Romania, kupčíkoneite coexists with minerals such as quartz, cosalite, galena, chalcopyrite, pyrite, hematite, as well as other rare bismuth sulfosalts. ## Localities The most important and best-documented occurrence of kupčíkoneite is its type locality – the Băița mining area (also known as Rézbánya) in Bihor County, Romania. This is the only confirmed locality from which well-studied specimens of this mineral originate.
Rarity
Very rare
For collectors
## Quality Criteria The quality of a kupčíkoneite specimen primarily depends on the abundance and visibility of the acicular crystal aggregates. The most prized samples are those where tangled, metallic "hairs" of kupčíkoneite create a clear contrast with bright quartz or other host rock. Association with other rare minerals is also important. Due to its microscopic nature, the purity and size of individual crystals are not key criteria. ## Popular Localities The only source of collector specimens is the historical type locality in the Băița mining area in Romania. Specimens from this location are highly sought after by collectors specializing in mineral systematics and rare species.
Care and storage
## Cleaning Kupčíkoneite specimens are extremely delicate and susceptible to mechanical damage. Cleaning should be kept to an absolute minimum. If necessary, compressed air (from a safe distance) can be used to remove dust. Avoid contact with water and any chemical agents. ## What to Avoid Avoid ultrasonics, steam cleaners, acids, detergents, and solvents. The mineral is sensitive to oxidation, so it should be protected from moisture and chemical pollutants in the air. It should not be heated or exposed to sudden temperature changes. ## Storage It is recommended to store specimens in sealed, airtight "micromount" boxes, away from light, moisture, and contaminants. Due to the fragility and small size of the crystals, avoid touching them with fingers or any tools.