Gurzhiite

Chemical formula: Al(U<sup>6+</sup>O<sub>2</sub>)(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>F·10H<sub>2</sub>O

Gurzhiite is an extremely rare, water-soluble uranyl mineral, forming microscopic, yellow tabular crystals.

## Characteristics Gurzhiite is a hydrated aluminum uranyl sulfate. It occurs as extremely small, tabular or platy crystals, reaching sizes up to 0.2 mm, which often form radial aggregates or rosettes. It is a secondary mineral, forming in the oxidation zones of uranium deposits. Due to its water solubility, it is unstable in humid environments. ## Physical Properties Gurzhiite crystals exhibit a yellow luster. The mineral is very soft, and its hardness is too low to be measured by standard methods. It is light, with a density slightly over 2 g/cm³. ## Colors and Varieties Gurzhiite has a characteristic, bright yellow color. No varieties have been distinguished. ## History and Name The mineral was named in honor of Vladislav Vyacheslavovich Gurzhiy (born 1984), a Russian crystallographer and crystal chemist from St. Petersburg State University, for his contributions to the mineralogy of uranium and technetium. It was approved by the IMA in 2018, and its discovery was described in 2020. ## Uses Gurzhiite, due to its extreme rarity, instability, and microscopic size, has no practical application. It is solely of scientific interest and is an object of interest for specialized collectors of uranium minerals.

Properties

Mohs hardness
1
Luster
Vitreous
Streak
Light yellow
Density
2.184
Cleavage
Perfect on {010}
Fracture
Micaceous
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Gurzhiite is identified based on its unique chemical composition (aluminum uranyl sulfate), bright yellow color, crystal habit (small, tabular crystals forming rosettes), and water solubility. Its identification requires advanced analytical methods, such as X-ray diffraction (XRD) and spectroscopy (EDS). ## Distinguishing from Similar Minerals It can be confused with other yellow secondary uranyl minerals, such as zippeite, uranophane, or meta-autunite. A key distinguishing feature is its immediate solubility in water, which is not typical for most uranyl sulfates and silicates. Final differentiation is only possible through chemical analysis. ## Crystal Forms It forms very small, thin, tabular crystals with a platy habit, elongated along one axis. These crystals often combine into radial aggregates, fans, and spherical rosettes.

Geological environment

## Genesis Gurzhiite is a secondary mineral that crystallizes at low temperatures from aqueous solutions rich in uranium, aluminum, and sulfates. It forms as a result of weathering and oxidation of primary uranium ores (uraninite) in the presence of clay minerals (source of aluminum) and pyrite (source of sulfates). Its formation is limited to dry conditions that allow for water evaporation and salt crystallization. ## Mineral Associations It co-occurs with other secondary uranium minerals, such as meta-autunite, uranophane, as well as with gypsum, quartz, and clay minerals. ## Localities The only known occurrence of this mineral (type locality) is the Byk uranium mine, located near Mount Byk on the Stavropol Plateau in the Russian North Caucasus.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, the quality of a specimen is primarily determined by the richness and development of the crystal aggregates. The most desirable specimens are those with clearly visible, well-formed rosettes or radial clusters on a contrasting matrix. The size of the crystals, although always small, is also important – the larger they are, the more valuable the specimen. ## Popular Localities The only source of gurzhiite specimens is its type locality – the Byk mine in Russia. All specimens available on the collector's market come from this single location.

Care and storage

## Cleaning This mineral must absolutely not be cleaned wet. It is water-soluble, so contact with water, even in the form of a damp cloth, will destroy the specimen. Cleaning is only possible mechanically, dry, using a soft brush or carefully using a photographic air blower to remove dust. ## What to Avoid Contact with water and any moisture must be strictly avoided. Storage in a humid environment (e.g., a basement) will lead to its disintegration. As a uranium mineral, it is radioactive and should be handled with appropriate precautions (avoid inhaling dust, wash hands after contact). ## Storage Gurzhiite specimens must be stored in sealed, dry containers, preferably with a desiccant (e.g., silica gel). They should be kept away from other minerals that could be damaged by its potential decay or that could damage it. Due to radioactivity, it should be stored in a designated place, away from areas of permanent human habitation.

Sources

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