Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence - Type Locality In Wales
Chemical Composition: Lead copper thiosulphate hydroxide hydrate
Chemical Formula: Pb2+5(OH)5[Cu+(S6+O3S2-)3](H2O)2
Method(s) of Verification: described as a new species from Frongoch Mine on the basis of EMP, IR and XRD data.
Introduction: an unusual post-mining supergene mineral formed during oxidation of galena-bearing veinstone within mine dumps. Steverustite typically forms colourless to white, lath-like crystals that aggregate to form fibrous fan-like bundles to 1.5 mm across. Associated species include sphalerite, galena, covellite, cerussite, anglesite, hemimorphite, susannite, bechererite and caledonite (Cooper et al., 2009).
Occurrence in Wales: Cooper et al. (2009) described the new species steverustite based on material from the dumps of Frongoch Mine, near Devil's Bridge in Ceredigion. Somewhat surprisingly - for a new mineral species - the descriptive paper (Cooper et al., 2009) also lists ten other localities where it has been identified. Seven of these are Welsh sites, but it only ever occurs as microcrystals.
- Bwlch-glas Mine, Tal-y-bont, Ceredigion: the only in-situ occurrence of steverustite reported by Cooper et al. (2009). 17 samples are known, all collected from a vein exposed in the upper adit level.
- Esgairhir Mine, Tal-y-bont, Ceredigion: six samples are recorded (Cooper et al., 2009) from the dumps of this prolific supergene mineral producing site.
- Frongoch Mine, Devil's Bridge, Ceredigion: at this the type locality, steverustite, forms fibrous fan-like bundles of fibrous to acicular crystals in small cavities in quartz veins with other supergene species (Cooper et al., 2009).
- Hendrefelin Mine, Ysbyty Ystwyth, Ceredigion: Cooper et al. (2009) reported that six samples are known from the dumps of this mine.
- Llangynog Mine, Llangynog, Powys: rarely found in material on the mine dump. Only two samples are known, one with bechererite in association (Cooper et al., 2009).
- Llechweddhelyg Mine, Penrhyncoch, Ceredigion: the dumps of this small mine are one of the most productive for steverustite. Cooper et al. (2009) record that 38 samples are known from this site.
- Nantycar Mine, Rhayader, Powys: according to Cooper et al. (2009), four samples of steverustite are known to have been collected from the dumps at this mine.
- Penybanc Mine, Tal-y-bont, Ceredigion: Cooper et al. (2009) state that three samples of steverustite have been identified from the dumps of Penybach (sic) Mine, Talybont.
- Cooper, M.A., Hawthorne, F.C. and Moffatt, E., 2009. Steverustite, Pb2+5(OH)5[Cu+(S6+O3S2-)3](H2O)2, a new thiosulphate mineral from the Frongoch Mine Dump, Devils Bridge, Ceredigion, Wales. Mineralogical Magazine. 73, 235-250.