Autunita
Autunita is a mineral with formula Ca(UO₂)₂(PO₄)₂·10-12H₂O, in the Fosfatos group. This specimen comes from Cunha Baixa Mine, Cunha Baixa, Mangualde, Viseu, Portugal and joined the Terrium collection in 1985.
Description
Large, well-defined tabular autunite crystals of intense yellow–green colour, some to 3×3 mm. The crystals are locally transparent, with vitreous lustre, lying flat on brown matrix. Under ultraviolet light they show very strong green fluorescence, typical of the species. Radioactive: 4.50 µSv/h at close range.
History of this specimen
It comes from the former collection of Carlos Prieto Paramio; he bought it from Carlos Tiago Alves (Portuguese dealer) at the Hotel Meliá show (Madrid) in December 1985 for 750 pesetas. With the original handwritten label. Since 2025 it has been in my collection.
About Autunita
Autunite is a hydrated uranyl phosphate that forms in the oxidation zones of uranium deposits, on granitic rocks and hydrothermal veins. It is valued for well-defined tabular crystals and intense green fluorescence, one of the species' most characteristic features.
About the locality
The Cunha Baixa Mine, in Mangualde (Viseu), was the largest uranium operation in Portugal and one of the most important in Europe. Known for large, high-quality autunite crystals, it closed in the 1990s after decades of activity. Today it is a worldwide classic for collectors of radioactive minerals.
Technical data
- Catalogue No.
- 0180
- Composition
- Ca(UO₂)₂(PO₄)₂·10-12H₂O
- Name
- Autunita
- Group
- Fosfatos
- Category
- Núcleus Ardens
- Matrix
- Matriz silícea con recubrimientos ferruginosos
- Mine
- Cunha Baixa Mine
- District / Municipality
- Cunha Baixa
- Province
- Mangualde
- Region
- Viseu
- Country
- Portugal
- Size (cm)
- 5 x 4.8 x 3
- Weight
- 86.4 g
- Acquired
- 1985
- Ex-collection
- Carlos Tiago Alves (Portugal) → Carlos Prieto Paramio
- Etymology
- From the toponym Autun (France), the type locality where it was described in 1852.
- Quality
- Notable
- Value trend
- Al alza