Galeaclolusite

Chemical formula: Al₆(As⁵⁺O₄)₃(OH)₉(H₂O)₄·8H₂O

Galeaclolusite is a very rare, hydrated aluminum arsenate, forming microscopic, colorless crystals in the form of needles and laths.

## Characteristics Galeaclolusite is a very rare mineral from the arsenate group, chemically classified as a hydrated basic aluminum arsenate. It occurs as microscopic, colorless or white crystals, most often forming acicular or bladed forms. These crystals are usually grouped into small, radial aggregates or scattered on the surface of the host rock. Due to its size, a microscope is essential for its observation and identification. ## Physical Properties Galeaclolusite crystals exhibit a vitreous luster. The mineral's density is approximately 2.27 g/cm³. It is a very brittle mineral. Due to the microscopic size of the crystals, determining its hardness on the Mohs scale is impossible. ## Colors and Varieties This mineral is colorless to white. No colored or commercial varieties have been distinguished. ## History and Name The name "galeaclolusite" comes from the combination of the Latin words *galea* (helmet), *clavis* (key), and *lustrum* (cave), which refers to the coat of arms of the commune of Le Pradet in France, where its type locality is situated. The mineral was described and approved by the International Mineralogical Association (IMA) in 2011. ## Applications Galeaclolusite has no industrial applications. Its significance is purely scientific and collectible, as a very rare and unique micromineralogical specimen.

Properties

Luster
Vitreous
Density
2.27
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of galeaclolusite under amateur conditions is practically impossible. It requires advanced analytical techniques, such as Raman spectroscopy or X-ray diffraction (XRD), to confirm its chemical composition and crystal structure. Visually, under high magnification, characteristic, tiny, acicular crystals can be observed. ## Distinguishing from Similar Minerals This mineral can be confused with other secondary arsenates found in similar environments, such as pharmacolite, mansfieldite, or conichalcite in their microcrystalline forms. Definitive differentiation is only possible based on chemical and crystallographic analysis. ## Crystal Forms Galeaclolusite crystallizes in the orthorhombic system. It forms very small, elongated crystals with an acicular or bladed habit, which often combine into small, radial or tangled aggregates.

Geological environment

## Genesis Galeaclolusite 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-bearing solutions and aluminum minerals under low temperature and pressure conditions. Its formation is associated with the activity of waters within old mine workings. ## Mineral Associations This mineral co-occurs with other rare arsenates and sulfates. In its type locality, it was found in association with arsenogoyazite, olivenite, agardite-(Y), brochantite, gypsum, and tennantite-(Zn), among others. ## Localities The only confirmed and described occurrence of galeaclolusite in the world is its type locality: the Cap Garonne mine in Le Pradet, Var department, France. This is a historic copper and lead mine, known for the occurrence of many rare secondary minerals.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, the collectible value of galeaclolusite primarily depends on the quality of the specimen at the microscopic scale. Most prized are samples with rich, well-formed, and undamaged aggregates of acicular crystals, clearly visible against a contrasting host rock. Confirmation of the mineral's identification is also important. ## Popular Localities The only source of galeaclolusite specimens is the Cap Garonne mine in France. Specimens from this locality are highly sought after by collectors specializing in rare minerals and micromounts.

Care and storage

## Cleaning Galeaclolusite specimens are extremely delicate and susceptible to mechanical damage. Cleaning should be kept to an absolute minimum. If necessary, compressed air can be used from a safe distance to remove loose dust particles. Any contact with water, chemicals, or tools should be avoided. ## What to Avoid Contact with water and other liquids, which can dissolve or damage the microscopic crystals, must be strictly avoided. The mineral is sensitive to changes in temperature and humidity. It should not be heated or exposed to direct sunlight. Vibrations and shocks can easily destroy the brittle aggregates. ## Storage Specimens should be stored exclusively in specialized "micromount" boxes, which protect them from dust, shocks, and humidity changes. The box should be tightly sealed and stored in a stable environment, away from heat and light sources.

External references

Sources

Read more