Natrouranospinite
Chemical formula: Na<sub>2</sub>(U<sup>6+</sup>O<sub>2</sub>)<sub>2</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>·5H<sub>2</sub>O
A rare uranium mineral from the meta-autunite group, forming characteristic square, yellowish-green tabular crystals with strong fluorescence.
Properties
- Mohs hardness
- 2.5
- Luster
- Vitreous, Pearly
- Streak
- Pale yellow
- Density
- 3.58
- Cleavage
- Perfect on {001}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Tetragonal
Diagnostic features
## Identification Key diagnostic features include the square, tabular habit of crystals, lemon-yellow to greenish-yellow color, perfect cleavage in one direction, and very strong, yellowish-green fluorescence under UV light. Strong radioactivity is also an important indicator. ## Distinguishing from Similar Minerals Natrouranospinite is visually almost identical to other minerals from the meta-autunite group, such as metauranocircite (more green, contains barium), metazeunerite (contains copper), or uranospinite itself (contains calcium). Reliable differentiation of these minerals is almost exclusively possible using advanced analytical methods, such as EDS spectroscopy or X-ray diffraction (XRD). ## Crystal Forms Crystals are thin-tabular with a square or octagonal outline. They usually occur as single, scattered flakes on the host rock or form fan-shaped, radial, and rosette-like aggregates. Also found as coatings and earthy masses.
Geological environment
## Genesis It is a secondary mineral, forming in the oxidation (weathering) zones of hydrothermal uranium-arsenic deposits. It forms as a result of sodium-rich waters acting on primary uranium minerals, such as uraninite, in the presence of arsenic derived from the oxidation of arsenopyrite or other sulfarsenides. ## Mineral Associations It co-occurs with other secondary uranium minerals, such as metazeunerite, uranospinite, trögerite, walpurgite, as well as with uraninite, quartz, fluorite, and hematite. ## Localities The most important localities worldwide include the historical type locality in Johanngeorgenstadt in the Ore Mountains (Saxony, Germany). Other known occurrences include the Sophia mine near Wittichen in the Black Forest (Germany) and the area around Wilson Lake in the Gjoa Haven district (Nunavut, Canada).
Rarity
Rare
For collectors
## Quality Criteria The most prized specimens are those with well-formed, sharp, square crystals of intense, lemon-yellow color, set on a contrasting rock matrix. Rich crystal groups forming fans or rosettes enhance their attractiveness. Crystal size rarely exceeds a few millimeters, so specimens with larger flakes are particularly sought after. ## Popular Localities Classic and most desired specimens by collectors come from historical mines in Saxony, Germany, especially from Johanngeorgenstadt. However, they are rarely available on the market.
Care and storage
## Cleaning Specimens should not be cleaned wet. Only gentle dust removal with a soft brush or compressed air from a safe distance is permissible. ## What to Avoid Absolutely avoid contact with water, which can dissolve and destroy the delicate crystals. The mineral is sensitive to humidity changes – in dry air, it can dehydrate, losing water from its structure, leading to dulling and disintegration. Protect from high temperatures and chemicals. As a uranium mineral, it is strongly radioactive, so exposure should be limited, hands should be washed after every contact, and it should not be stored in areas of constant human presence. ## Storage Store in sealed, airtight containers (e.g., "membrane boxes" or plastic boxes) to help maintain stable humidity and protect the fragile crystals. Due to radioactivity, specimens should be kept away from other radiation-sensitive minerals and in a designated area, preferably in a lead-lined container, away from bedrooms and living rooms.