Szilagyiite

Chemical formula: NaCa<sub>3</sub>(U<sup>6+</sup>O<sub>2</sub>)(CO<sub>3</sub>)<sub>3</sub>(Se<sup>4+</sup>O<sub>3</sub>)F(H<sub>2</sub>O)<sub>6</sub>

Szilagyiite is an extremely rare, radioactive uranyl mineral, distinguished by its intense yellow color and occurrence as microscopic, radial aggregates.

## Characteristics Szilagyiite is a complex, hydrated fluoride, carbonate, and selenite of sodium, calcium, and uranyl. It occurs as microscopic, radial aggregates or spherulites, reaching sizes up to 0.2 mm. Individual crystals have the form of lamellae or needles. Due to its size, visual features are observable only under high magnification. ## Physical Properties Szilagyiite crystals exhibit an intense yellow color and vitreous luster. They are transparent to translucent. Hardness and density have not been precisely measured due to the small size and rarity of the material. As a uranium mineral, it is strongly radioactive. ## Colors and Varieties This mineral is monochromatic – it occurs exclusively in shades of intense yellow. No varieties have been distinguished. ## History and Name Szilagyiite was discovered in the dumps of the Bota-Burnari uranium mine in the Apuseni Mountains, Romania. It was described and approved as a new mineral species by the International Mineralogical Association (IMA) in 2021 (IMA2021-042). The name honors Robert Szilágyi (born 1980), a Romanian mineral collector who found the first samples of this mineral.

Properties

Luster
Vitreous
Streak
Yellow
Transparency
Transparent to Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of szilagyiite is impossible without advanced analytical methods. Preliminary field identification relies on its intense yellow color, characteristic of secondary uranium minerals, and strong radioactivity. Confirmation requires chemical analysis (EDS) and X-ray diffraction (XRD). ## Differentiation from Similar Minerals Szilagyiite can be confused with many other yellow secondary uranium minerals, such as tyuyamunite, carnotite, or autunite. "Eyeball" differentiation is impossible. Chemical composition analysis is crucial, which will show the simultaneous presence of selenium, carbon, and fluorine, a unique combination for this mineral. ## Crystal Forms It forms radial aggregates and spherulites composed of very small, lamellar or acicular crystals.

Geological environment

## Genesis Szilagyiite is a secondary mineral that formed as a result of the weathering (oxidation) of primary uranium ores in the presence of solutions rich in selenium, carbonates, and fluorine. It forms in the oxidation zone of uranium deposits. ## Mineral Associations At the type locality (locus typicus), it co-occurs with other secondary uranium minerals, such as andersonite, liebigite, schröckingerite, as well as calcite and quartz. ## Localities The only confirmed occurrence of szilagyiite in the world is the Bota-Burnari mine (also known as Băița) in Bihor County, Romania.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, the collector's value of szilagyiite primarily depends on the richness and aesthetics of the aggregates on the rock matrix. Specimens with clearly formed, radial spherulites of intense color, contrasting well with the host rock, are most prized. Due to its extreme rarity, any authentic specimen is considered extremely valuable. ## Popular Localities The only source of specimens is the type locality in Romania.

Care and storage

## Cleaning Due to its extreme rarity, small crystal size, and fragility, mechanical cleaning is not recommended. Specimens should be protected from dust in sealed containers. ## What to Avoid As a uranyl mineral, it is sensitive to direct sunlight, which can cause its slow dehydration and change in properties. Contact with water and chemicals should be avoided. Due to strong radioactivity, exposure should be limited, and it should be stored away from areas of permanent human presence, using appropriate safety measures. ## Storage Szilagyiite specimens must be stored in specialized, lead-lined containers to protect against radiation. It is best to keep them in stable, dry conditions, away from light and temperature fluctuations. Clear labeling of the container as radioactive material is recommended.

Sources

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