Arsenuranospathite
Chemical formula: Al(U<sup>6+</sup>O<sub>2</sub>)<sub>2</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>F·20H<sub>2</sub>O
Arsenuranospathite is a rare, radioactive secondary uranium mineral, forming thin, platy crystals with a characteristic yellow color.
Description
## Characteristics Arsenuranospathite is a mineral belonging to the group of hydrated uranyl arsenates. It occurs as thin, rectangular or square tablets, which often form fan-shaped or foliated aggregates. Crystals are usually small, reaching a few millimeters. The mineral is transparent to translucent, with an intense, lemon-yellow or greenish-yellow color. ## Physical Properties It is a very soft mineral, with a hardness of about 2 on the Mohs scale, meaning it can be scratched with a fingernail. It has perfect cleavage in one direction, which causes it to easily split into thin, flexible lamellae. The luster on cleavage surfaces is strongly pearly, while on other faces and fractures it is vitreous. The calculated density is approximately 3.23 g/cm³. ## Colors and Varieties This mineral occurs in uniform shades, from lemon-yellow to greenish-yellow. No color or commercial varieties are distinguished. ## History and Name Arsenuranospathite was described as a new mineral species in 1978 by Kurt Walenta. Its name refers to its chemical composition - the presence of arsenic (arsen-) and uranium (uran-) - and to its platy form and structural similarity to uranospathite (-spathite), which is its phosphate analogue. ## Uses Due to its rarity, small crystal size, and high radioactivity and toxicity, arsenuranospathite has no industrial applications. It is solely an object of scientific and collecting interest, sought after by specialists collecting uranium minerals.
Diagnostic features
## Identification Key diagnostic features of arsenuranospathite include its characteristic habit in the form of thin, square or rectangular tablets, intense yellow color, and strong pearly luster on cleavage surfaces. It is highly radioactive, which can be easily detected with a Geiger counter. It also exhibits strong, yellowish-green fluorescence under ultraviolet light (both shortwave and longwave). ## Distinguishing from Similar Minerals Arsenuranospathite is visually almost identical to its phosphate analogue, uranospathite. Reliable differentiation of these two minerals requires chemical analysis (EDS/WDS) to determine the dominance of arsenic over phosphorus. It can be confused with other secondary uranium minerals, such as zeunerite or autunite, but it differs from them in crystal form (zeunerite forms thicker, tabular crystals, and autunite often occurs in fan-shaped aggregates with different symmetry).
Geological environment
## Genesis It is a secondary mineral, formed in the oxidation (weathering) zones of hydrothermal uranium deposits. It forms as a result of the slow alteration of primary uranium minerals, mainly uraninite, in an arsenic-rich environment. ## Mineral Associations Arsenuranospathite most commonly occurs in association with other secondary uranium minerals. Its most common associated minerals are uranospathite, zeunerite, metazeunerite, as well as primary uraninite, quartz, and hematite. ## Localities This is a very rare mineral. The most important and classic occurrence (type locality) is the uranium deposit in Menzenschwand in the Black Forest (Germany). The best, well-formed specimens in the world come from there. It is also known from several other, few localities worldwide where similar geological conditions exist.
Rarity
Very rare
Collector aspects
## Quality Criteria The most prized arsenuranospathite specimens are those characterized by sharply defined, well-formed crystals with an intense, pure color. Rich groups of crystals forming aesthetic, fan-shaped aggregates on a small rock matrix are highly valued. Due to its rarity, even microscopic but well-identified crystals are valuable for specialized collectors. ## Popular Localities The only significant locality from a collector's point of view is the Krunkelbach mine in Menzenschwand (Black Forest, Germany). Specimens from this locality are considered exemplary for this species.
Care and storage
## Cleaning The mineral is extremely delicate, soft, and has perfect cleavage. Wet cleaning should be avoided. Any contaminants, such as dust, should only be removed with a soft brush or very carefully, using a stream of compressed air from a distance. ## What to Avoid Arsenuranospathite is a highly radioactive and toxic mineral due to its uranium and arsenic content. Direct skin contact, inhalation of dust, and any mechanical processing must be strictly avoided. It is sensitive to heat, which can cause loss of crystallization water and destruction of its structure. It should be protected from water and chemicals. ## Storage Specimens should be stored in tightly sealed, lead or thick plastic containers, clearly labeled as radioactive and toxic material. These containers should be kept in an area isolated from permanent human presence, preferably in a ventilated cabinet. It should be stored away from other minerals that may be damaged by radiation.