Barahonaite-(Fe)

Chemical formula: (Ca,Cu₂+,Na,Fe₃+,Al)₁₂Fe₃+₂(As₅+O₄)₈(OH,Cl)x·nH₂O

Barahonaite-(Fe) is a very rare, secondary arsenate, forming microscopic, spherical aggregates of an intensely green color.

## Characteristics Barahonaite-(Fe) is a hydrated arsenate from the apatite arsenate group, distinguished by the presence of iron in its composition. It occurs as extremely small, spherical or hemispherical aggregates, rarely exceeding 0.1 mm in diameter. These aggregates have a radial-fibrous internal structure. Due to the microscopic size of the crystals, its visual features are difficult to observe without specialized equipment. ## Physical properties The crystals are too small to reliably determine their hardness, density, or other mechanical properties. The luster is described as vitreous to silky, and the mineral is translucent. ## Colors and varieties This mineral is characterized by a vivid, emerald-green or apple-green color. No color or commercial varieties are known. ## History and name Barahonaite-(Fe) was recognized as a new mineral by the IMA in 2006 (IMA2006-033). Its name honors Antonio Barahona (b. 1937), a Spanish mineral collector who provided samples for study. The suffix "-(Fe)" refers to the dominance of iron at a specific site in its crystal structure. It was described by a research team including Joan Viñals and Jordi Ibáñez-Insa. ## Uses Barahonaite-(Fe) has no industrial applications. It is of purely scientific significance and is of interest to specialized collectors of rare minerals (so-called micromounts).

Properties

Mohs hardness: 2
Luster: Vitreous to Silky
Streak: Pale green
Density: 3.45
Cleavage: None
Fracture: Uneven
Transparency: Translucent
Crystal system: Hexagonal

Diagnostic features

## Identification In practice, the identification of Barahonaite-(Fe) is based on its characteristic appearance – microscopic, green spheres with a radial internal structure. The locality (Dolores mine in Spain) and co-occurrence with other rare arsenates are also crucial. Final confirmation requires advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS). ## Distinguishing from similar minerals It can be confused with other secondary green copper and iron minerals, such as agardite, olivenite, or conichalcite, which can form similar aggregates. Barahonaite-(Fe) differs from them by its unique chemical composition (it is a calcium-iron arsenate) and specific crystallographic data, which cannot be verified without specialized equipment. ## Crystal forms This mineral exclusively forms spherical or hemispherical aggregates with a radial-fibrous structure. Individual, well-formed crystals are not observed.

Geological environment

## Genesis Barahonaite-(Fe) is a secondary mineral, formed in the oxidation zones (gossans) of polymetallic deposits rich in arsenic. It forms as a result of the weathering of primary sulfides and arsenides, in a low pH environment. It forms directly on the surface of gangue, most often on quartz. ## Mineral associations It co-occurs with other secondary arsenate minerals, such as carminite, scorodite, arseniosiderite, beudantite, as well as goethite, hematite, and quartz. ## Localities The only confirmed occurrence of this mineral in the world (type locality) is the Dolores mine in the municipality of Pastrana, in the province of Guadalajara, Castilla-La Mancha region, Spain.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of Barahonaite-(Fe) specimens is assessed based on the size and number of spherical aggregates on the rock matrix. Samples with numerous, well-defined spherules of intense, emerald-green color, contrasting with a light quartz substrate, are most valued. The absence of damage to the delicate aggregates is also important. ## Popular localities All known collector specimens come from a single location in the world – the Dolores mine in Spain. This is the only source of this mineral.

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to extreme delicacy and reactivity, contact with water, even distilled, and any mechanical cleaning, including with soft brushes, should be avoided. ## What to avoid Contact with all chemicals, acids, and detergents must be strictly avoided. The mineral is sensitive to changes in humidity and temperature. It should not be heated or exposed to direct sunlight, which can cause dehydration and color change. ## Storage Barahonaite-(Fe) specimens should be stored under stable conditions, preferably in sealed, lockable "micromount" boxes or in containers with humidity control. Protect from vibrations and shocks.

Sources

IMA Mineral List (CNMNC)