Uranocircite

Chemical formula: Ba(U₆+O₂)₂(PO₄)₂·₁₀H₂O

Uranocircite is a rare uranyl and barium mineral, belonging to the autunite group, characterized by an intense yellowish-green color and strong fluorescence.

## Characteristics Uranocircite is a uranyl and barium phosphate mineral, belonging to the autunite group. It usually occurs as small, tabular crystals with a platy habit or in granular aggregates and crusts. Its color is characteristic, ranging from yellowish-green to yellow, often with a canary-yellow tint in transmitted light. This mineral is radioactive. ## Physical Properties The hardness of uranocircite on the Mohs scale is 2-2.5, making it a relatively soft mineral. It has a pearly luster, and its transparency ranges from transparent to translucent. The specific gravity is 3.46 g/cm³. ## Colors and Varieties The typical color of uranocircite is yellowish-green or yellow. In transmitted light, a pale, canary-yellow color is often observed. No specific commercial or color varieties are distinguished beyond natural variations in shade. ## History and Name Uranocircite was described in 1877. The mineral's name is derived from its chemical composition, indicating the presence of uranium and zirconium, although later analyses showed that zirconium is not a key component. The name reflects the initial, erroneous belief in the presence of this element. ## Uses Uranocircite has no industrial applications due to its rarity and radioactivity. It is a mineral of purely collectible and scientific importance, being of interest due to its chemical composition and physical properties.

Properties

Mohs hardness: 2-2.5
Luster: Pearly
Streak: Żółtawo-biała
Density: 3.46
Cleavage: Perfect on {001}; distinct on {100} {010}
Fracture: Nierówny
Transparency: Transparent,Translucent
Crystal system: Tetragonal

Diagnostic features

## Identification Uranocircite can be identified by its characteristic yellowish-green color, pearly luster, and low hardness. It often occurs as thin, tabular crystals. Strong fluorescence under ultraviolet light is also a diagnostic feature. ## Distinguishing from Similar Minerals Uranocircite can be confused with other uranyl minerals, such as autunite or torbernite. It is distinguished from autunite by the presence of barium instead of calcium. It differs from torbernite by the presence of phosphate instead of arsenate and by its color, which in the case of torbernite is usually greener. Chemical analysis is often necessary for unambiguous identification. ## Crystal Forms Uranocircite usually forms thin, tabular crystals with a platy habit. It often occurs in scaly, granular aggregates or as crusts on other minerals.

Geological environment

## Genesis Uranocircite is a secondary mineral, forming in the oxidation zones of uranium deposits. It forms as a result of the weathering of primary uranium minerals in the presence of phosphates and barium, often in water-rich environments. ## Mineral Associations Uranocircite often co-occurs with other uranyl minerals, such as autunite, torbernite, meta-autunite, metatorbernite, and also with uranium minerals like uraninite. It can also be found in association with phosphate and barite minerals. ## Localities Known localities of uranocircite include the Bergen mine in Saxony (Germany), where it was first described. It also occurs in other localities in Germany, as well as in the Czech Republic, France, USA (e.g., Arizona, Utah), and other regions of the world where uranium deposits are found.

Rarity

Uncommon

For collectors

## Quality Criteria The most prized uranocircite specimens are those with well-formed, large, and distinct crystals, an intense and uniform yellowish-green color, and high transparency. Specimens with distinct fluorescence are also highly sought after. The absence of mechanical damage and presence on an attractive matrix increase its collector's value. ## Popular Localities The most prized uranocircite specimens come from historical localities in Saxony, Germany, especially from the areas around Freiberg and Schneeberg. Other important locations include mines in the Czech Republic and some deposits in the United States.

Care and storage

## Cleaning Due to the softness and radioactivity of uranocircite, cleaning should be kept to a minimum. It is best to use a soft, dry brush to gently remove dust. Avoid water and chemical solutions, which can damage the mineral's surface. ## What to Avoid Avoid contact with water, acids, bases, and other chemical substances. The mineral is sensitive to high temperatures and prolonged exposure to direct sunlight, which can lead to changes in color or structure. Due to radioactivity, prolonged and direct skin contact should be avoided. ## Storage Uranocircite should be stored in a tightly sealed container, preferably in a dry and cool place, away from other minerals that could scratch it. Due to radioactivity, it is recommended to store it in a separate, ventilated space, away from living areas, especially if the collection is large.