Uranospinite

Properties

Mohs hardness

2-3

Luster

Pearly, Vitreous

Streak

Very pale yellow

Density

3.45

Cleavage

On {001}, perfect; on {100}, distinct.

Fracture

Micaceous

Transparency

Translucent

Crystal system

Tetragonal

Diagnostic features

## Identification The most important diagnostic feature of uranospinite is its intense, lemon-yellow to greenish-yellow color and characteristic, strong, green or yellowish-green fluorescence under ultraviolet light (both shortwave and longwave). The typical form of thin, square crystals gathered in fan-shaped aggregates is also very helpful in identification. The mineral is strongly radioactive, which can be confirmed with a Geiger counter. ## Distinguishing from similar minerals - **Autunite:** It is practically indistinguishable visually. Autunite is a phosphate, and uranospinite is an arsenate. The difference can only be determined by chemical analysis (EDS, XRD). Autunite often has a slightly more greenish hue, but this is not a rule. - **Zeunerite:** It has a similar habit and color, but it is a copper uranyl arsenate. It usually has a more intensely green color. - **Torbernite:** It is a copper uranyl phosphate, has an intensely green color and does not fluoresce under UV light. - **Uranophane:** It forms acicular or fibrous crystals in radial aggregates, rarely tabular. It has a similar color but a different crystal form. ## Crystal forms Uranospinite crystallizes in the tetragonal system, forming thin, tabular crystals with a square cross-section. These crystals often arrange themselves into fan-shaped, radial, or almost spherical aggregates. It also occurs as lamellar aggregates, rosettes, and as thin crusts on host rocks.

Geological environment

## Genesis Uranospinite is a secondary mineral, forming in the oxidation (weathering) zones of uranium ore deposits. It forms as a result of the alteration of primary uranium minerals, such as uraninite, in the presence of arsenic- and calcium-rich waters. It is a typical mineral of uranium paragenesis in hydrothermal deposits and some pegmatites. ## Mineral associations It most often co-occurs with other secondary uranium minerals, especially those from the same group. Typical associated minerals include zeunerite, metazeunerite, uranophane, and also primary uraninite. It can also occur in association with quartz, fluorite, and various sulfides. ## Localities The most important localities worldwide, from which good quality specimens originate, are: - **Germany:** The historical type locality in Schneeberg (Saxony), where it was discovered, and other mines in the Black Forest. - **USA:** Mines in Utah, Nevada, and Arizona provide excellent crystalline specimens. - **France:** Specimens are known from the Lodève area and the Massif Central. - **Czech Republic:** Occurs in the Jáchymov region. - **Poland:** Trace occurrences have been noted in the Sudetes, including the vicinity of Kowary and Kletno.

Rarity

Not very common

For collectors

## Quality criteria The most highly prized uranospinite specimens are characterized by sharply defined, well-formed crystals with a large surface area, gathered into aesthetic, fan-shaped or rosette aggregates. The intensity and purity of the lemon-yellow color is a key factor. Specimens on a contrasting rock matrix are more desirable than loose aggregates. Minimal dehydration is also important – shiny and translucent specimens are much more valuable than dull and weathered ones. ## Popular localities Although the mineral was discovered in Germany, currently the most valued specimens by collectors come from some mines in Utah, USA. They provide large, well-formed, and intensely colored crystalline aggregates.

Care and storage

## Cleaning Uranospinite specimens are extremely delicate and brittle. Cleaning should be kept to an absolute minimum. If necessary, a soft brush can be used to remove dust or compressed air from a safe distance. Avoid contact with water, which can lead to dehydration and destruction of the crystals. ## What to avoid - **Water and moisture:** Uranospinite contains water in its crystal structure (it is a hydrated mineral). Storage in too dry an environment can cause water loss, leading to dulling, crumbling, and disintegration of the crystals. Avoid washing in water. - **High temperature and sunlight:** Similar to dry air, these can accelerate the dehydration process. Specimens should be protected from direct sunlight and heat sources. - **Chemicals:** Avoid contact with acids and other chemical agents. - **Vibrations and impacts:** Crystals are very brittle and have perfect cleavage, making them susceptible to mechanical damage. ## Storage It is recommended to store specimens in closed, airtight containers (e.g., "perky box" type), which help maintain a stable humidity level. It is advisable to place a small piece of sponge or cotton wool soaked with a few drops of water (but not directly touching the specimen) in the container to prevent drying out. Due to radioactivity, specimens should be stored away from areas of permanent human presence, in labeled containers.

External references

• https://www.mindat.org/min-4113.html

Sources

• Mindat - Uranospinite
• IMA Mineral List (CNMNC)