Arsenosabugalite

Chemical formula: H₀.₅Al₀.₅(U₆+O₂)₂(As₅+O₄)₂·₈H₂O

A very rare, strongly radioactive secondary uranium mineral of the meta-autunite group, being the arsenate analogue of sabugalite.

## Characteristics Arsenosabugalite is a very rare mineral from the arsenate class, belonging to the meta-autunite group. Chemically, it is a hydrated aluminium uranyl arsenate. It crystallizes in the triclinic system. Like other members of this group, it usually forms small, flaky or tabular crystals, often aggregated in crusts. Due to the high uranium content in its crystal lattice, it is a strongly radioactive mineral, which requires special precautions during research and storage. ## Physical properties This mineral exhibits properties typical of members of the meta-autunite group. It is characterized by perfect cleavage in one direction, giving its crystals a distinct micaceous habit. It is a brittle and relatively soft mineral. Due to the water content in its structure, it can undergo dehydration in dry conditions. ## Colors and varieties Arsenosabugalite assumes colors in shades of yellow, often with a distinct greenish tint, which is very characteristic of many secondary uranyl minerals. It has no distinguished varieties. ## History and name The name of the mineral directly refers to its chemical composition - the presence of the arsenate anion - and its close structural relationship to sabugalite, which is its phosphate analogue. The type locality for this mineral is the Hubbard Homestead Mine in Mesa County (Colorado, USA). ## Uses Due to its extreme rarity and the small size of its aggregates, arsenosabugalite has no industrial significance as a uranium ore. It is solely a scientific curiosity and a very rare collector's item for advanced collectors specializing in the systematics of radioactive minerals.

Properties

Crystal system: Triclinic

Diagnostic features

## Identification Visual identification of arsenosabugalite is extremely difficult. The mineral exhibits strong radioactivity, which can be easily confirmed with a dosimeter. For definitive species confirmation, advanced X-ray diffraction (XRD) studies and chemical analyses (e.g., EDS) demonstrating the presence of uranium, arsenic, and aluminium are required. ## Distinguishing from similar minerals Visually, this mineral is practically indistinguishable from other yellow and greenish-yellow minerals of the autunite and meta-autunite groups, such as autunite, meta-autunite, zeunerite, nováčekite, or sabugalite itself. Distinction requires confirmation of the presence of aluminium and arsenic alongside the absence of phosphorus in the structure. ## Crystal habits It forms microscopic, thin tabular or flaky crystals. It most commonly occurs in the form of scaly aggregates, powdery coatings, or thin incrustations on the surface of gangue rocks.

Geological environment

## Origin Arsenosabugalite is a secondary mineral. It forms in the oxidation zones of uranium deposits, where primary uranium minerals undergo weathering and alteration under the influence of hydrothermal solutions or meteoric waters rich in arsenate ions and aluminium. ## Mineral associations It co-occurs with other secondary uranium minerals, clay minerals, and iron oxides and hydroxides, which are typical of oxidized ore zones. ## Localities The mineral is known from very few localities worldwide. The most important site and type locality is the Hubbard Homestead Mine in the Beaver Mesa area (Gateway Mining District) in Mesa County, Colorado, USA.

Rarity

Extremely rare

For collectors

## Quality criteria In the case of such rare minerals, the value of a specimen is primarily determined by analytically confirmed species identity and the surface area of the matrix rock covered by arsenosabugalite aggregates. The development of crystals visible under magnification additionally increases collector value. ## Popular localities The only significant source of reference specimens on the collector market is the type locality at the Hubbard Homestead Mine in Colorado (USA).

Care and storage

## Cleaning Specimens should not be cleaned mechanically or washed in water due to their brittleness and solubility. Only very gentle dusting with a soft brush is permissible, while maintaining strict safety rules associated with handling radioactive materials. ## What to avoid Contact with water, acids, and moisture must be strictly avoided. The mineral can undergo dehydration in a dry environment, so specimens should be protected from direct sunlight and heat sources. ## Storage Due to strong radioactivity (presence of uranium) and toxicity (presence of arsenic), specimens must be stored in airtight, lead-lined containers or special display cabinets shielding ionizing radiation. The room should be well-ventilated to prevent radon accumulation. Inhalation of dust must be avoided, and hands should be washed thoroughly after any contact with the container.

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External references

https://www.mindat.org/min-498764.html