Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Chemical Composition: Iron sulphate hydroxide hydrate
Chemical Formula: Fe3+(SO4)(OH).5H2O
Method(s) of Verification: Cae Coch Mine - XRD & wet chemical analysis; Parys Mountain - XRD.
- Supergene: post-mining oxidation & weathering deposits
Scanning electron micrograph of matted hair-like fibroferrite on gypsum from Cae Coch Mine. National Museum of Wales specimen (NMW 2002.9G.M.4). © National Museum of Wales.
Introduction: fibroferrite forms in highly acidic conditions, particularly in the altered portions of sulphide ore bodies and on the walls of underground mine workings in the post-mining supergene environment.
Occurrence in Wales: fibroferrite is known from two localities in North Wales, where it has formed in underground workings as a product of the post-mining oxidation of pyrite (Johnson & Jenkins, 1979; Jenkins et al., 2000). Given the number of localities where similar environments exist throughout North and Central Wales, but where the post-mining mineralogy remains to be investigated, it is anticipated that further occurrences may well come to light.
- Cae Coch Mine, Trefriw, Gwynedd: fibroferrite forms copious mounds with jarosite and, more rarely, copiapite on the floor of the mine (Johnson et al., 1979).
- Parys Mountain, Anglesey: fibroferrite is present in minor amounts, with other iron sulphates, in overhangs and recesses and other sites protected from the elements within the two major opencasts (Jenkins et al., 2000).
- Jenkins, D. A., Johnson, D. B. & Freeman, C., 2000. Mynydd Parys Cu-Pb-Zn mines: mineralogy, microbiology and acid mine drainage. pp. 161-179. In: Environmental Mineralogy: Microbial Interactions, Anthropogenic Influences, Contaminated Land and Waste Management (Cotter-Howells, J. D., Campbell, L. S., Valasami-Jones, E. & Batchelder, M., eds.). The Mineralogical Society of Great Britain & Ireland, London.
- Johnson, D.B., Kelso, W.I., & Jenkins, D.A., 1979. Bacterial streamer growth in a disused pyrite mine. Environmental Pollution, 18, 107-118.