Autunita
Autunita is a mineral with formula Ca(UO₂)₂(PO₄)₂·10-12H₂O, in the Fosfatos group. This specimen comes from Mina Assunçao, Aldeia Nova, Ferreira de Aves, Viseu, Portugal and joined the Terrium collection in 2012.
Description
Abundant, well-defined tabular autunite crystals of greenish-yellow, accompanied by bluish-green metatorbernite, on massive milky quartz. The crystals form dense aggregates with a satiny vitreous lustre and strong colour contrast against the matrix. Protected with Paraloid B-72.
History of this specimen
Collected by hand in 2012 by Antonino Bueno y Patiño at the well-known open-pit mine at Assunçao, known for the quality of its finds. Patiño insisted I should take this piece, assuring me it was better than 137, although visually I was more drawn to the other one for its terminated quartz columns. I was just starting to collect and did not fully understand his criterion, until he explained the difference lay in the number of crystals—many more in this one—and in the presence of torbernite, a detail I had already noticed. To encourage me, he knocked off about €15 and I ended up taking both: this one on the first day and 137 on the last.
About Autunita
Autunite is a secondary uranium phosphate that forms in oxidised zones, commonly associated with metatorbernite, as here. The contrast between the two minerals reinforces the visual and scientific value of the piece. Fluorescent and radioactive, it is a classic of Assunçao.
About the locality
It comes from a former open-pit operation at Assunçao, Portugal, now inactive. Finds depended on hand searching, and this specimen represents one of the most aesthetic associations recorded in the area.
Technical data
- Catalogue No.
- 0136
- Composition
- Ca(UO₂)₂(PO₄)₂·10-12H₂O
- Name
- Autunita
- Group
- Fosfatos
- Category
- Núcleus Ardens
- Matrix
- Cuarzo lechoso masivo
- Associations
- metatorbernita
- Mine
- Mina Assunçao
- District / Municipality
- Aldeia Nova
- Province
- Ferreira de Aves
- Region
- Viseu
- Country
- Portugal
- Size (cm)
- 9 x 7 x 4
- Weight
- 265 g
- Acquired
- 2012
- Ex-collection
- Patiño
- Etymology
- From French "Autun", the type locality near which it was discovered; the root of the name is retained in multiple languages.
- Quality
- Muy buena
- Value trend
- Estable