Čejkaite

Chemical formula: Na₄U₆+O₂(CO₃)₃

Čejkait is a rare, secondary uranyl mineral, forming microscopic, acicular crystals of an intense greenish-yellow color and strong fluorescence.

## Characteristics Čejkait is a mineral from the uranyl carbonate group, chemically a hydrated sodium uranyl carbonate. It occurs as very fine, acicular or fibrous crystals that form coatings, crusts, and rosette-like aggregates on rock surfaces. Due to the microscopic size of the crystals, its macroscopic features are difficult to observe; it most often appears as dusty or felt-like aggregates. ## Physical Properties Čejkait crystals are extremely small and brittle. The mineral exhibits intense, yellow-green fluorescence under ultraviolet light (both shortwave and longwave), which is its characteristic feature. It is highly radioactive, typical for uranium minerals. ## Colors and Varieties This mineral has a characteristic light green to greenish-yellow color. No color varieties or commercial varieties are distinguished. ## History and Name Čejkait was discovered in the uranium mine in Jáchymov, Czech Republic. It was described and approved as a new mineral species by the International Mineralogical Association (IMA) in 2002 (IMA2002-064). The mineral is named in honor of the Czech chemist and mineralogist, Jiří Čejka (born 1929), for his contributions to the study of uranium mineral chemistry and infrared spectroscopy in mineralogy. ## Uses Due to its rarity, microscopic size, and radioactivity, čejkait has no practical or commercial applications. It is solely an object of scientific and collecting interest for specialized collectors of uranium minerals.

Properties

Mohs hardness: 2-3
Luster: Vitreous
Streak: Light yellow
Density: 3.53
Cleavage: None
Fracture: Uneven
Transparency: Transparent
Crystal system: Trigonal

Diagnostic features

## Identification The key diagnostic features of čejkait are its mode of occurrence (fine, acicular crystals forming coatings), light greenish-yellow color, and very strong yellow-green fluorescence under UV light. However, definitive identification requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD), due to its resemblance to other secondary uranium minerals. ## Distinguishing from Similar Minerals Čejkait can be confused with other secondary uranyl minerals of similar appearance and color, such as andersonite, liebigite, bayleyite, or schröckingerite. Andersonite crystallizes in the trigonal system and often forms more defined, pseudoregular crystals. Liebigite and bayleyite are also greenish-yellow but have different diffraction patterns. Schröckingerite often forms larger, tabular aggregates. Distinguishing them in the field is practically impossible without a fluorescence test, and final identification requires laboratory analysis. ## Crystal Forms Čejkait forms very fine, elongated, acicular crystals, which typically do not exceed a few tens of micrometers in length. These crystals combine into dense, tangled aggregates with a felt-like or cotton-like appearance, as well as radial rosettes and thin coatings on the host rock.

Geological environment

## Genesis Čejkait is a secondary mineral, forming in the oxidation zones of uranium deposits. It forms as a result of the action of sodium carbonate-rich waters on earlier uranium minerals under conditions of low temperature and pressure. It is a typical mineral found in mining environments, on mine walls and dumps, where weathering processes are accelerated. ## Mineral Associations In its type locality in Jáchymov (Czech Republic), čejkait occurs in association with other secondary uranium minerals, such as schröckingerite, andersonite, and liebigite. It may also co-occur with gypsum and calcite. ## Localities The most important and type locality (discovery site) is the Svornost mine in Jáchymov, Karlovy Vary Region, Czech Republic. It has also been identified in several other locations worldwide, including the Krunkelbach uranium mine (Menzenschwand) in the Black Forest, Germany, and the Give-a-Damn mine in Juab County, Utah, USA.

Rarity

Very rare

For collectors

## Quality Criteria The quality of čejkait specimens is assessed based on the richness and coverage of the host rock surface by microcrystalline aggregates. The most desirable specimens are those with dense, well-formed, felt-like or rosette-like clusters of intense, vivid color. Contrast with a dark host rock (e.g., with uraninite) also enhances the visual value of the specimen. Due to its microscopic nature, the size of individual crystals is not a key criterion. ## Popular Localities By far the most valued and classic specimens come from the type locality - Jáchymov in the Czech Republic. Specimens from this location are considered exemplary for this mineral.

Care and storage

## Cleaning The mineral is extremely delicate and brittle. It should not be cleaned mechanically or chemically. Any attempts at cleaning may destroy the microscopic crystals. If dust removal is necessary, a photographic air blower can be used to gently blow it off from a safe distance. ## What to Avoid Avoid contact with water and any chemicals. The mineral is sensitive to moisture. Due to radioactivity, direct skin contact, inhalation of dust, and storage in areas of constant human presence should be avoided. Always wash hands after handling the specimen. ## Storage Čejkait specimens must be stored in sealed, well-labeled containers, preferably made of plastic (e.g., perky box type), to prevent the spread of radioactive dust. These containers should be kept away from other radiation-sensitive minerals and in a place secured from access by children and pets.

Sources

IMA Mineral List (CNMNC)