Coparsite

Chemical formula: Cu₂+₄O₂As₅+O₄Cl

Coparsite is a rare, secondary copper and arsenic mineral, forming tiny, platy crystals of an intensely green color.

## Characteristics Coparsite is a secondary copper arsenate with chlorine. It occurs as very small, thin, platy crystals, which rarely exceed 0.2 mm. These crystals form rosette-like or radial aggregates, as well as thin coatings and efflorescences on the surface of host rocks. Due to the small size of the crystals, its macroscopic features are difficult to observe without magnification. ## Physical Properties Coparsite crystals exhibit a vitreous luster. It is a brittle mineral, with a hardness estimated at approximately 3 on the Mohs scale. Due to the small size of the crystals, precise determination of physical properties, such as density or fracture, is very difficult. ## Colors and Varieties Coparsite is characterized by a vivid, emerald-green color. No color varieties or commercial varieties are known. ## History and Name The mineral's name refers to its chemical composition – the presence of copper (Latin: *cuprum*) and arsenic (*arsenicum*). It was first described in 2012 by Stuart J. Mills and co-workers based on material collected from the Maria Catalina mine in Chile. Approved by the International Mineralogical Association (IMA) under number 2011-057. ## Uses Coparsite has no industrial application. Its significance is purely scientific and collectible, being of interest to specialized collectors of rare minerals.

Properties

Mohs hardness: 3
Luster: Vitreous
Streak: Light green
Density: 4.45
Cleavage: Perfect on {100}
Fracture: Brittle
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of coparsite in field conditions is practically impossible due to its rarity and small crystal size. Recognition is based on its characteristic emerald-green color, the form of thin platy crystals forming rosette aggregates, and its co-occurrence with other secondary copper arsenates. Final identification requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS). ## Distinguishing from Similar Minerals Coparsite can be confused with many other green secondary copper minerals, such as euchroite, olivenite, conichalcite, or annabergite (nickel varieties). Differentiation with the naked eye is impossible. Coparsite is distinguished by its specific chemical composition (it is a hydrated copper arsenate-chloride) and characteristic crystal structure. ## Crystal Forms It forms very thin, platy crystals with a hexagonal or octagonal outline, elongated along the [010] axis. These crystals often combine into radial or rosette aggregates, and also form thin crusts on the host rock.

Geological environment

## Genesis Coparsite is a secondary mineral, formed in the oxidation zones (gossans) of copper and arsenic ore deposits. It forms as a result of weathering of primary minerals, such as chalcopyrite and arsenopyrite, under dry and saline conditions, typical of desert climates. ## Mineral Associations It most commonly co-occurs with atacamite, paratacamite, kelyanite, corderoite, quartz, barite, and hematite. These minerals together form a characteristic assemblage for oxidized deposits in arid climates. ## Localities The only confirmed and described occurrence (type locality) is the Maria Catalina mine, located approximately 40 km east of the city of Taltal in the Antofagasta region of Chile.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of coparsite specimens is primarily assessed based on the richness and size of crystal aggregates on the rock matrix. The most valued specimens are those with well-formed, clearly visible crystal rosettes of an intense, emerald-green color. Contrast with the matrix and the presence of rare associated minerals are also important. ## Popular Localities The only source of coparsite specimens is its type locality – the Maria Catalina mine in Chile. All specimens available on the collector's market originate from this single location.

Care and storage

## Cleaning Specimens should not be cleaned mechanically or chemically. The tiny crystals are extremely delicate and easily damaged. If cleaning is absolutely necessary, a soft brush can be carefully used to remove loose dust. ## What to Avoid Contact with water, acids, and all chemicals should be avoided. The crystals are very brittle, so shocks, impacts, and friction should be avoided. The specimen should not be exposed to ultrasound. ## Storage It is recommended to store specimens in stable conditions, in closed "micromount" boxes, which protect against dust, moisture, and mechanical damage. Areas with high humidity should be avoided.

Sources

IMA Mineral List (CNMNC)