Nickelzippeite
Chemical formula: Ni²⁺₂(U⁶⁺O₂)₆(S⁶⁺O₄)₃(OH)₁₀·16H₂O
A nickel uranyl sulfate from the zippeite group, forming characteristic yellow to brownish-yellow coatings and aggregates.
Properties
- Mohs hardness
- 5-5.5
- Density
- 0
- Transparency
- Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Nickelozippeite is most easily recognized by its characteristic, intense yellowish-green fluorescence under UV light. Its typical mode of occurrence is earthy, powdery coatings of yellow or brownish-yellow color, often on uraninite or host rock. Strong radioactivity is a key diagnostic feature. ## Distinguishing from Similar Minerals It can be confused with other minerals from the zippeite group (e.g., zippeite, cobaltozippeite, magnesiozippeite) and other secondary uranium minerals like uranophane or autunite. Differentiation from zippeite group members is usually impossible without advanced chemical analysis (EDS/WDS). It differs from autunite by weaker and different crystal structure (autunite forms distinct, tabular crystals). ## Crystal Forms It forms microscopic crystals with a bladed or acicular habit, which combine into rosette-like, spherulitic, or fibrous aggregates. Most commonly, it occurs as earthy and powdery coatings on rock surfaces.
Geological environment
## Genesis It is a secondary mineral, formed in the oxidation (weathering) zones of uranium deposits. It forms as a result of the reaction of acidic, sulfate-rich waters (produced from the oxidation of sulfides, e.g., pyrite) with primary uranium minerals (mainly uraninite) in the presence of nickel ions, derived from the weathering of nickel minerals (e.g., niccolite). ## Mineral Associations It co-occurs with other secondary uranium minerals, such as gypsum, uranopilite, johannite, fourmarierite, as well as with uraninite (as a primary mineral) and sulfides (pyrite, chalcopyrite, niccolite). ## Localities The most important and confirmed occurrences of this mineral are the historic Jáchymov mine in the Czech Republic (type locality) and several uranium mines in Utah, USA, including in the San Juan County (Delta, Lucky Strike mines) and Emery County areas.
Rarity
Rare
For collectors
## Quality Criteria For collectors, the most desirable specimens are those with rich, well-formed aggregates of intense, pure color. Specimens where nickelozippeite forms aesthetic contrasts with dark host rock or co-occurs with other rare uranium minerals are also highly valued. Due to the microscopic size of the crystals, the main criterion is the quality and abundance of the aggregates. ## Popular Localities The most classic and prized specimens come from the type locality in Jáchymov, Czech Republic. Specimens from the United States, particularly from mines in Utah, are also sought after by collectors specializing in radioactive minerals.
Care and storage
## Cleaning Nickelozippeite specimens are extremely delicate and fragile. Mechanical cleaning is highly inadvisable. Any dust should be removed very carefully, using a soft brush or a photographic air blower. Avoid contact with water, which can damage or dissolve the mineral. ## What to Avoid The mineral is highly radioactive – absolutely avoid inhaling dust and direct skin contact. Wash hands after every contact with the specimen. Do not store in places of permanent human presence (desks, bedrooms). Avoid all chemicals, high temperatures, and humidity. ## Storage Specimens should be stored in sealed, lead-lined or thick-walled plastic containers, appropriately labeled as radioactive material. Store away from other radiation-sensitive minerals and in a dry place.