Uranofana-α Alfa
Uranofana-α is a mineral with formula Ca(UO₂)₂(SiO₃)(OH)₂·5H₂O, in the Silicatos group. This specimen comes from Mina Eureka, Castell-estaó, Lleida, Catalunya, España and joined the Terrium collection in 1995.
Description
Pulverulent yellow crusts of lemon-yellow uranophane-α alternating with emerald-green zeunerite zones. Gives 1.14 µSv/h at close range.
History of this specimen
Second radioactive addition to the collection. Without my knowing, it came with first-rate provenance. Its first owner was Martí Rafel Fontanals (an institutional figure of the Grup Mineralògic Català GMC and editor of "Paragenesis"). Later, through exchange, it formed part of the collection of Eduard Artime (a reference in the documentation of localities, creator of MinerAtlas).
About Uranofana-α
NEOFORMATION. Uranophane-α is a silicate usually regarded as rare, yet at Eureka it stands out as one of the most abundant species. It is the metastable structural phase of uranophane, analytically confirmed with a crystal structure distinct from the stable beta form. However, it is very likely that the zeunerite stabilised as metazeunerite on dehydration after leaving the saturated environment of the gallery. Zeunerite signals the local presence of copper and arsenic derived from sulphide alteration, uncommon in other parts of the "mine".
About the locality
Eureka functions as a very unusual enclave. It is not a conventional mine but trial workings opened by the JEN in the 1960s. It is a Triassic "red-bed" (Buntsandstein) stratum with carbonaceous layers and plant remains that trapped uranium from the mineralising fluids that passed through it. From 1962, investigative works began with several adits and small galleries, but the deposit did not enter exploitation because the uranium was too localised and did not support continuous production. This is what matters for collecting: Eureka is a world reference for neoformation uranium carbonates and silicates. Notably, minerals such as abellaite, andersonite and uranophane continue to grow on the walls: they were not there 100 years ago. This occurs because many uranium salts and carbonates dissolve and recrystallise readily in the humid microclimate of the galleries.
Technical data
- Catalogue No.
- 0245
- Composition
- Ca(UO₂)₂(SiO₃)(OH)₂·5H₂O
- Name
- Uranofana-α
- Variety
- Alfa
- Group
- Silicatos
- Category
- Núcleus Ardens
- Associations
- zeunerita
- Mine
- Mina Eureka
- District / Municipality
- Castell-estaó
- Province
- Lleida
- Region
- Catalunya
- Country
- España
- Size (cm)
- 5 x 4 x 2
- Weight
- 35 g
- Acquired
- 1995
- Ex-collection
- Martí Rafel Fontanals > Eduard Artime
- Etymology
- From the Greek "ouranos" (uranium) and "phanos" (appearance), after its characteristic colour.
- Quality
- Muy buena
- Value trend
- Estable
Related specimens
- Abellaíta — España
- Abernathyita — España
- Abernathyita — España
- Abernathyita — España
- Aerenita — España
- Aerinita (fibrosa) — España
- Analcima — España
- Analcima — España