Bariopharmacoalumite

Chemical formula: Ba₀.₅Al₄(As₅+O₄)₃(OH)₄·₄H₂O

Bariopharmacoalumite is a rare arsenate from the pharmacosiderite group, distinguished by the presence of barium and forming characteristic cubic crystals.

## Characteristics Bariopharmacoalumite is a hydrated barium aluminum arsenate, belonging to the pharmacosiderite group. This mineral forms very small, but well-formed, cubic crystals, rarely exceeding 0.2 mm in size. These crystals typically occur as scattered aggregates or small druses in depressions of the host rock. Due to its size, a microscope is essential for its observation. ## Physical Properties Bariopharmacoalumite crystals are characterized by a vitreous luster. The mineral's hardness on the Mohs scale is approximately 3, classifying it as a soft mineral. It is transparent to translucent. The density calculated based on the chemical formula and unit cell parameters is 3.21 g/cm³. ## Colors and Varieties Bariopharmacoalumite is usually colorless, less often white or pale yellow. No named varieties of this mineral have been distinguished. ## History and Name The mineral's name refers to its chemical composition – the presence of barium (Bario-) and its structural and chemical similarity to pharmacosiderite (-pharmacoalumite). It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2010. It was described by a team of researchers, including Igor V. Pekov, based on specimens found in Greece. ## Uses Bariopharmacoalumite has no industrial applications. Its significance is purely scientific and collectible, being an object of interest for specialized collectors of rare minerals and micromounts.

Properties

Mohs hardness: 3
Luster: Vitreous
Streak: White
Density: 3.21
Cleavage: None
Fracture: Conchoidal
Transparency: Transparent to translucent
Crystal system: Cubic

Diagnostic features

## Identification Amateur identification of bariopharmacoalumite is practically impossible. A key visual feature, visible under a microscope, is the characteristic, perfectly formed cubic crystals. Definitive identification requires advanced analytical methods, such as Raman spectroscopy or chemical analysis using an electron microprobe (EDS/WDS). ## Distinguishing from Similar Minerals Bariopharmacoalumite can be confused with other minerals from the pharmacosiderite group, such as pharmacosiderite, natropharmacoalumite, or pharmacosiderite. Distinguishing them based on appearance is impossible and requires specialized chemical analysis to determine the dominant cation (barium, potassium, sodium, iron). ## Crystal Forms This mineral crystallizes in the form of regular, sharply terminated cubes. Crystals are usually isolated or form small, loose aggregates on the rock surface.

Geological environment

## Genesis Bariopharmacoalumite is a secondary mineral, forming in the oxidation (weathering) zones of ore deposits rich in arsenic. It forms as a result of reactions between solutions containing arsenic, aluminum, and barium with minerals of the surrounding rocks. ## Mineral Associations This mineral co-occurs with other secondary arsenates. In the type locality (Hilarion mine, Greece), it was found in association with olivenite, conichalcite, arseniosiderite, goethite, quartz, and other minerals from the pharmacosiderite group. ## Localities The most important and type locality for bariopharmacoalumite is the Hilarion mine in the Attica region, Greece. This is currently the only confirmed and well-documented locality for this mineral worldwide.

Rarity

Very rare

For collectors

## Quality Criteria The quality of collectible specimens depends on several factors. Most prized are specimens with sharp, well-formed, and transparent crystals of regular, cubic shape. Contrast with the rock matrix and the richness of aggregates are also important. Due to the microscopic size of the crystals, even small but distinct and aesthetically arranged groups are considered valuable. ## Popular Localities The only source of collectible specimens is the Hilarion mine in Lavrion (Greece). Specimens from this locality are the standard for this mineral.

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the extreme delicacy and small size of the crystals, any other method, including the use of water or brushes, risks their irreversible destruction. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and any vibrations or impacts. The mineral is soft and brittle, and its crystals are easily susceptible to mechanical damage. It should not be heated, as it contains water in its structure. ## Storage Bariopharmacoalumite specimens, typically in the form of micromounts, should be stored exclusively in dedicated, sealed perky boxes, which protect them from dust, moisture, and mechanical damage. Avoid exposure to direct sunlight.

Sources

IMA Mineral List (CNMNC)