Kapellasite
Chemical formula: Cu<sup>2+</sup><sub>3</sub>Zn<sup>2+</sup>(OH)<sub>6</sub>Cl<sub>2</sub>
Kapellasite is a rare mineral from the halide group, a copper and zinc hydroxychloride, forming characteristic blue-green aggregates.
Properties
- Mohs hardness
- ~3.5
- Luster
- Vitreous
- Streak
- Pale green
- Density
- 3.98
- Cleavage
- Good on {0001}
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification Kapellasite is recognized mainly by its characteristic, vivid blue-green color, its occurrence in spherical or radial aggregates, and its locality. It reacts with hydrochloric acid, releasing gas, which is a diagnostic but destructive feature for the sample. ## Differentiation from Similar Minerals It can be confused with other secondary copper minerals, such as malachite, chrysocolla, atacamite, or paratacamite. It differs from malachite by the absence of reaction with acids without CO₂ bubble evolution (kapellasite reacts with HCl, but differently). It is harder than chrysocolla and has a more defined crystalline structure. Final differentiation from very similar minerals of the atacamite group (e.g., herbertsmithite) requires advanced chemical (EDS) or X-ray (XRD) analyses. ## Crystal Forms It forms microscopic, acicular or bladed crystals, most often occurring as spherical, radial aggregates. Less commonly found as crusts or rosettes.
Geological environment
## Genesis Kapellasite is a secondary mineral, formed in the oxidation zones of copper and zinc ore deposits, especially in chloride-rich environments. It forms as a result of the action of saline seawater on ancient copper and lead metallurgical slags, as well as in natural oxidation zones within host rocks. ## Mineral Associations It most commonly co-occurs with other secondary minerals, such as atacamite, paratacamite, herbertsmithite, gypsum, anglesite, cerussite, as well as with relics of primary minerals like galena or pyrite. ## Localities The most important and classic locality, which is also the type locality, is the historical dumps and slags in the Lavrion area of Greece. It has also been found in the Cap Garonne mine in France, in mines in Chile (e.g., Casualidad mine, Antofagasta region), and in Australia (Dome Rock mine, South Australia).
Rarity
Very rare
For collectors
## Quality Criteria The most prized by collectors are specimens with well-formed, spherical aggregates of intense, blue-green color, contrasting with the rock matrix. The size of the aggregates and the absence of damage are also important. Specimens with well-documented localities, especially from the type locality (Lavrion), are particularly sought after. ## Popular Localities By far the most sought-after and classic specimens come from Lavrion, Greece. Material from the Cap Garonne mine in France and from the Atacama Desert in Chile also provides high-quality collector specimens.
Care and storage
## Cleaning Kapellasite specimens are very delicate and sensitive. Only compressed air or a very soft brush should be used to remove dust. Any contact with water, especially acids, is inadvisable and can lead to damage or dissolution of the mineral. ## What to Avoid Avoid ultrasonic cleaners, all chemical agents, detergents, and solvents. The mineral is sensitive to high temperatures and sudden changes in temperature. Prolonged exposure to direct sunlight can cause color fading. ## Storage It is recommended to store specimens in closed, dry containers or display cases, away from sources of moisture and contaminants. To avoid mechanical damage, it should be kept separate from harder minerals.