Metauranospinite
Chemical formula: Ca(U⁶⁺O₂)₂(As⁵⁺O₄)₂·8H₂O
Meta-uranospinite is a rare uranium mineral from the meta-autunite group, forming characteristic yellow-green, tabular crystals with strong fluorescence.
Properties
- Mohs hardness
- 2-3
- Color
- Greenish yellow, yellowish green
- Luster
- Vitreous, Pearly
- Streak
- pale yellow
- Density
- 3.94
- Cleavage
- {001), also good on (010)
- Fracture
- Uneven
- Transparency
- Transparent,Translucent
- Crystal system
- Tetragonal
Diagnostic features
## Identification Key diagnostic features of meta-uranospinite include its lemon-yellow to yellow-green color, thin-tabular crystal habit, excellent cleavage in one direction, and strong yellow-green fluorescence under UV light. It is a secondary mineral, occurring as coatings and aggregates on rocks in the oxidation zones of uranium deposits. ## Distinguishing from Similar Minerals Meta-uranospinite is visually almost identical to many other minerals of the meta-autunite group, such as metazeunerite (contains copper instead of calcium, usually greener), meta-autunite (contains phosphorus instead of arsenic), or uranospinite (higher degree of hydration). Reliable distinction of these minerals is possible almost exclusively through advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Crystal Forms Crystals are thin-tabular, with a square or octagonal outline. They usually form fan-shaped, radial, or rosetted aggregates. They also occur as scaly coatings, crusts, and microcrystalline aggregates.
Geological environment
## Genesis Meta-uranospinite is a secondary mineral that crystallizes in the oxidation (weathering) zones of hydrothermal uranium ore deposits rich in arsenic. It forms under low temperature and pressure conditions as a result of the alteration of primary uranium minerals, such as uraninite. ## Mineral Associations It often co-occurs with other secondary uranium minerals, especially from the autunite and meta-autunite groups, such as uranospinite, metazeunerite, meta-autunite, as well as with uranophane, gypsum, and quartz. ## Localities The most important occurrences of meta-uranospinite are in Germany, in the Schneeberg and Johanngeorgenstadt areas of Saxony. It is also known from the Czech Republic (Jáchymov), France (e.g., Les Sagnes mine in the Massif Central), and several localities in the USA, including San Juan County in Utah.
Rarity
Rare
For collectors
## Quality Criteria The most prized specimens by collectors are those with well-formed, sharp crystals forming aesthetic, fan-shaped or rosetted aggregates. An intense, lemon-yellow color and absence of mechanical damage are important. Large, rich coverings on a contrasting rock matrix significantly increase the specimen's value. Strong fluorescence is an additional asset. ## Popular Localities Classic and most sought-after specimens come from historical localities in Saxony, Germany (Schneeberg, Johanngeorgenstadt). These are considered exemplary for this mineral.
Care and storage
## Cleaning Specimens should only be cleaned very carefully, using compressed air to remove dust. Contact with water is absolutely inadvisable, as it can lead to rehydration and destruction of the crystals. A very soft brush can be used to remove loose contaminants. ## What to Avoid Avoid contact with water and other liquids, high humidity, and ultrasonic cleaners. The mineral is very brittle, so it must be protected from impacts and vibrations. As a uranium mineral, it is radioactive and requires safe handling – avoid inhaling dust and wash hands after each contact. ## Storage Meta-uranospinite should be stored in a dry place, preferably in a sealed, airtight box (e.g., a "membrane box") or in a display cabinet away from sources of moisture. To prevent dehydration or excessive hydration, a desiccant (silica gel) can be placed nearby. Due to its radioactivity, specimens should be stored away from areas of permanent human habitation.