Calciopharmacoalumite

Chemical formula: Ca₀.₅Al₄(As₅+O₄)₃(OH)₄·₅H₂O

Calciofarmacoalumite is a rare calcium aluminum arsenate, forming small, cubic crystals with a vitreous luster, occurring in the oxidation zones of ore deposits.

## Characteristics Calciofarmacoalumite is a hydrated calcium aluminum arsenate, belonging to the pharmacoalumite group. This mineral forms very small, but well-formed crystals with an isometric, most often cubic habit. Crystals rarely exceed 0.5 mm in size and usually occur as single cubes or small aggregates grown on the surface of the host rock. Due to its size, magnification is necessary for its observation. ## Physical Properties Calciofarmacoalumite crystals are characterized by a vitreous luster. They are transparent to translucent. The mineral's hardness is low, estimated at about 2.5 on the Mohs scale, which means it is quite brittle and delicate. Its calculated density is 2.59 g/cm³. ## Colors and Varieties The mineral is usually colorless or white. No colored or commercial varieties have been distinguished. ## History and Name Calciofarmacoalumite was first described in 2011 by Stuart J. Mills, Andrew G. Christy, Joël Brugger, Ian E. Grey, and William D. Birch. The name refers to its chemical composition – the presence of calcium (Latin: *calcius*) – and its structural similarity to other minerals of the pharmacoalumite group. The Cap Garonne mine in Le Pradet, Var, France, was recognized as the type locality (locus typicus). ## Uses Calciofarmacoalumite has no industrial application. Its significance is purely scientific and collectible, being an object of interest for collectors specializing in rare minerals and micromounts.

Properties

Mohs hardness: 2.5
Luster: Vitreous
Streak: White
Density: 2.59
Cleavage: None
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Cubic

Diagnostic features

## Identification The characteristic feature of calciofarmacoalumite is its very small, but usually perfectly formed cubic crystals. Vitreous luster and most often colorless appearance are also helpful in identification. Due to its size, definitive identification requires stereoscopic magnification, and certainty is provided by chemical analysis (EDS) or X-ray analysis (XRD). ## Distinguishing from Similar Minerals Calciofarmacoalumite can be confused with other minerals from the pharmacoalumite group, such as pharmacoalumite (potassium) or natropharmacoalumite (sodium). Distinguishing them based on visual characteristics is practically impossible and requires advanced laboratory tests to determine the dominant cation (calcium, potassium, or sodium). ## Crystal Forms The mineral crystallizes in the isometric system, forming almost exclusively crystals in the shape of a cube {100}. It occurs as single, overgrown crystals or small, loose groups on the surface of other minerals.

Geological environment

## Genesis Calciofarmacoalumite is a secondary mineral, formed in the oxidation (weathering) zones of ore deposits rich in arsenic. It forms as a result of reactions between arsenic-containing solutions, derived from the weathering of arsenopyrite or other sulfarsenides, and aluminum and calcium minerals in the gangue. ## Mineral Associations This mineral co-occurs with other secondary arsenates. At the type locality (Cap Garonne), it was found in association with olivenite, tennantite, chalcopyrite, kankite, scorodite, arseniosiderite, mawbyite, pushcharovskite, and gartrellite. ## Localities The most important and confirmed occurrences of this rare mineral are: * **France** - Cap Garonne mine in Le Pradet, Var (type locality). * **Australia** - Kintore Opencut mine in Broken Hill, New South Wales.

Rarity

Very rare

For collectors

## Quality Criteria For collectors of calciofarmacoalumite, the most important criteria are the sharpness and size of the crystals, although these rarely exceed fractions of a millimeter. Specimens with well-formed, sharp cubes that are transparent and free from damage are most valued. A contrasting matrix on which the crystals have grown also enhances the visual attractiveness of the specimen. Due to the nature of the mineral, it is almost exclusively of interest to micromineral (micromounts) collectors. ## Popular Localities Specimens from the type locality, the Cap Garonne mine in France, are the most classic and sought after by specialists. Material from Broken Hill, Australia, is also valued in collecting circles.

Care and storage

## Cleaning Specimens should be cleaned very carefully, exclusively with compressed air to remove dust. Due to the small size of the crystals and their fragility, mechanical contact, including brushes, should be avoided. The use of water is not recommended. ## What to Avoid Avoid contact with all chemicals, including acids and detergents. The mineral is sensitive to shocks and impacts, which can easily damage the delicate crystals. It should not be heated or exposed to sudden temperature changes. ## Storage The safest storage method is to place the specimen in a sealed "micromount" box, which protects it from dust, moisture, and mechanical damage. Exposure should be away from sources of vibration.

Sources

IMA Mineral List (CNMNC)