Chernikovite
Chemical formula: (H<sub>3</sub>O)(U<sup>6+</sup>O<sub>2</sub>)(PO<sub>4</sub>)·3H<sub>2</sub>O
Chernikovite is a hydrated uranyl phosphate, valued by collectors for its intense yellow-green color and strong fluorescence under UV light.
Properties
- Mohs hardness
- 2-2.5
- Luster
- Vitreous, Pearly
- Streak
- Light yellow
- Density
- 3.25
- Cleavage
- Perfect on {001}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Tetragonal
Diagnostic features
## Identification The most important diagnostic feature of chernikovite is its intense, yellow-green fluorescence under ultraviolet light (both shortwave and longwave). Its characteristic bright daylight color, tabular crystal habit, and strong radioactivity, easily detectable with a Geiger counter, are also distinctive. ## Differentiation from Similar Minerals Chernikovite is visually almost identical to meta-autunite and other minerals from this group (e.g., torbernite, uranocircite). Reliable differentiation from meta-autunite, with which it forms a solid solution, is practically only possible using advanced analytical methods such as X-ray diffraction (XRD). ## Crystal Forms Chernikovite crystals are thin-tabular, with a square or octagonal habit. They usually form fan-shaped, radial, or rosetted aggregates. They also occur as scaly aggregates, coatings, and crusts.
Geological environment
## Genesis Chernikovite is a secondary mineral, forming in the oxidation (weathering) zones of uranium ore deposits. It crystallizes from waters rich in uranium and phosphates, often in cracks and fissures of rocks such as granites, pegmatites, or sandstones containing organic matter. ## Mineral Associations This mineral often co-occurs with other secondary uranium minerals, such as autunite, meta-autunite, torbernite, uraninite (which is its primary mineral), as well as with quartz, mica, and clay minerals. ## Localities Significant specimens come from Perus, São Paulo state, Brazil (type locality). It also occurs in several locations in the USA, including South Dakota and Utah. It is also known from Italy (Sardinia), Germany (Saxony), and Argentina.
Rarity
Rare
For collectors
## Quality Criteria The most prized specimens by collectors are those with well-formed, sharp crystals forming aesthetic, rosetted or fan-shaped aggregates. The intensity and saturation of the yellow-green color significantly increase the value of the specimen. Contrast with the rock matrix and the absence of mechanical damage to the delicate crystals are also important. ## Popular Localities The locality in Perus (São Paulo, Brazil) is considered classic and yields the best specimens. Specimens from this locality are the standard for the species and fetch the highest prices on the collector's market.
Care and storage
## Cleaning Cleaning chernikovite specimens is generally not recommended due to their fragility and radioactivity. If absolutely necessary, compressed air can be used to remove dust. Contact with water, which can damage the mineral, should be avoided. ## What to Avoid Contact with water and chemicals must be strictly avoided. The mineral is sensitive to heat and direct sunlight, which can cause dehydration and loss of color. Due to radioactivity, exposure should be limited, and inhalation of dust should be avoided. ## Storage Chernikovite specimens must be stored in specialized, sealed, and appropriately labeled containers to protect against radiation. They should be kept away from other radiation-sensitive minerals, in a dry and dark place.