Šreinite
Chemical formula: Pb²⁺(U⁶⁺O₂)₄(Bi³⁺O)₃(PO₄)₂(OH)₇·4H₂O
Šreinite is an extremely rare, secondary uranyl and bismuth mineral, forming microscopic, yellow, tabular crystals.
Properties
- Mohs hardness
- 2-4
- Color
- Yellow with an orange tint
- Luster
- Vitreous
- Streak
- Pale yellow
- Density
- 0
- Cleavage
- Perfect on {010}
- Fracture
- Irregular/Uneven
- Transparency
- Opaque
- Crystal system
- Isometric
Diagnostic features
## Identification Identification of šreinite is based on its characteristic bright yellow color, the form of small, tabular crystals forming radial aggregates, and its occurrence in association with other secondary uranium and bismuth minerals. Definitive identification is only possible using advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Šreinite can be confused with many other yellow secondary uranyl minerals, such as uranophane, kasolite, or phosphuranylite. Visual differentiation is practically impossible. Key is the examination of its chemical composition, which shows the presence of both uranium and bismuth, as well as phosphorus. ## Crystal Forms The crystals are very small, thin, and tabular, with a bladed habit. They usually occur as radial or tangled aggregates, as well as thin crusts.
Geological environment
## Genesis Šreinite is a secondary mineral, forming in the oxidation zones of polymetallic hydrothermal deposits rich in uranium and bismuth. It forms as a result of weathering and alteration of primary uraninite and native bismuth ores in the presence of phosphate-rich solutions. ## Mineral Associations This mineral co-occurs with other secondary uranium and bismuth minerals. In its type locality (Jáchymov), it has been found in association with phosphuranylite, bismutite, beyerite, atelestite, walpurgite, uranophane, and gypsum, among others. It occurs on heavily weathered gangue rock containing quartz and hematite. ## Localities The only confirmed and described locality for šreinite in the world is its discovery site – the historic Rovnost I mine in Jáchymov, in the Karlovy Vary Region of the Czech Republic.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of šreinite specimens is primarily assessed based on the richness and aesthetics of the crystal aggregates. Most valued are specimens with clearly formed, radial groups of crystals that contrast well with the rock matrix. Due to the microscopic size of the crystals, their abundance on a given rock fragment is crucial. ## Popular Localities The only source of šreinite specimens is its type locality – Jáchymov in the Czech Republic. Material from this location is highly sought after by collectors specializing in mineral systematics, rare minerals, and micromounts.
Care and storage
## Cleaning Šreinite specimens should generally not be cleaned mechanically or chemically due to their extreme delicacy and small size. If cleaning is absolutely necessary, compressed air can be carefully used from a safe distance to remove loose dust particles. ## What to Avoid Avoid contact with water and all chemicals. The crystals are fragile and can be damaged by the slightest touch. As a radioactive mineral, it requires safe handling – avoid inhaling dust and wash hands after any contact. ## Storage Specimens should be stored in stable, tightly sealed "micromount" containers to protect them from mechanical damage and dust. Store away from other minerals that may be sensitive to radiation. The container should be labeled as containing radioactive material.