Eclarite
Chemical formula: (Cu²⁺,Fe²⁺)Pb²⁺₉Bi³⁺₁₂S²⁻₂₈
Eclarite is a rare lead, bismuth, copper, and iron sulfosalt, forming acicular crystals with a metallic luster.
Properties
- Mohs hardness
- 2.5-3.5
- Luster
- Metallic
- Streak
- Lead grey
- Density
- 6.75
- Cleavage
- Distinct on {010} poor on {0kl}
- Transparency
- Opaque
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Eclarite can be identified by its characteristic acicular or bladed crystals, often forming radial aggregates. Key features include a metallic luster, whitish-gray color, and a lead-gray streak. It is a soft and relatively heavy mineral. ## Distinguishing from Similar Minerals It can be confused with other acicular sulfosalts such as jamesonite, boulangerite, or bismuthinite. Differentiation often requires advanced analytical methods, such as chemical analysis (EDS) or X-ray diffraction (XRD). In field conditions, distinguishing it from similar minerals is practically impossible. ## Crystal Forms Eclarite forms elongated, acicular or bladed crystals with a rhombic cross-section. These crystals typically occur as radial, tangled, or chaotically arranged clusters and aggregates. Single, well-formed crystals are rarely observed.
Geological environment
## Genesis Eclarite is a hydrothermal mineral. It forms in ore veins that cut metamorphic rocks, such as schists. Its crystallization occurs under low to medium temperature conditions from solutions rich in bismuth, lead, sulfur, copper, and iron. ## Mineral Associations This mineral often co-occurs with other sulfides and sulfosalts. At the type locality (Bärenbad), it was found in association with quartz, pyrite, chalcopyrite, sphalerite, galena, as well as other, rarer bismuth sulfosalts. ## Localities The most important and type locality for eclarite is the Bärenbad mine in the Hollersbach Valley (Salzburg, Austria). It is a very rare mineral, and its occurrence has been confirmed in only a few places worldwide, but specimens from the type locality are the best known.
Rarity
Very rare
For collectors
## Quality Criteria Specimens with well-formed, undamaged, acicular crystals forming aesthetic, radial aggregates are most valued by collectors. Contrast with a light matrix rock (e.g., quartz) significantly enhances the visual appeal and value of the specimen. The size of the aggregates and the abundance of crystals on the matrix are key evaluation factors. ## Popular Localities By far, the most sought-after and valued eclarite specimens come from its type locality – the Bärenbad mine in Austria. Specimens from other locations are extremely rare on the collector's market.
Care and storage
## Cleaning Eclarite specimens are delicate and should be handled with care. Cleaning should be limited to gently removing dust with a soft brush or compressed air from a safe distance. Avoid contact with water and any chemicals. ## What to Avoid Eclarite is sensitive to chemicals, especially acids, which can damage it. Ultrasonic cleaners should be avoided, as they can destroy delicate crystal aggregates. As a sulfide, it may be susceptible to moisture and oxidation in the long term, so it should be protected from humid environments. ## Storage It is recommended to store eclarite specimens in closed, dry containers or display cases to protect them from dust, moisture, and mechanical damage. Due to its lead content, hands should be washed after handling the mineral.