Mineral Database
Thorianite
Crystal System: Cubic
Formula: ThO2
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Thorium oxide
Method(s) of Verification: Presteigne - EMPA (Parnell & Eakin, 1989)
Chemical Group:
- Oxides & Hydroxides
Geological Context:
- Sedimentary : diagenetic
- Igneous
Introduction: thorite is a uranium oxide mineral that forms a series with uraninite. It is most commonly found within pegmatites.
Occurrence in Wales: there is just one reported occurrence of thorianite from Wales.
Key Localities:
- Presteigne, Powys: thorianite, associated with thorite, has been identified as minute inclusions, 2-5 μm across, within spherical bitumen nodules in the Folly Sandstone, of Llandovery age, exposed in the Presteigne area of Powys (Parnell & Eakin, 1989). The nodules formed within the sediment although the source of the thorium is uncertain, a possible candidate being monazite nodules within the Ordovician and Silurian strata of the Welsh Basin.
References:
- Thorium-bitumen mineralization in Silurian sandstones, Welsh Borderland. Mineralogical Magazine, 53, 111-116.
