Crystal System: Hexagonal
Status of Occurrence: Confirmed Occurrence - 3rd UK recording
Chemical Composition: Hydrated manganese oxide with calcium
Chemical Formula: (Ca,Mn2+)Mn4+4O9.3H2O
Method(s) of Verification: identification of ranciéite is by XRD (no. NMW X-1552) and EDS (Cotterell and Jenkins, 2008).
- Oxides & Hydroxides
- Supergene: post-mining oxidation & weathering deposits
Stalactitic ranciéite (aggregate 10 cm across) forming on the roof of Dyffryn Adda adit level. D.A. Jenkins photo. © D.A. Jenkins.
Back-scattered electron image of dendritic ranciéite in polished section. National Museum of Wales specimen, no. NMW 2007.35G.M.1a. © National Museum of Wales.
Introduction: a weathering product of manganese deposits and manganese-bearing minerals, particularly in Ca-rich environments such as limestones. A solid solution series exists between ranciéite and takanelite.
Occurrence in Wales: the only account of ranciéite in Wales was made by Cotterell and Jenkins (2008) who reported the mineral occurring as stalactites in the main drainage adit at Parys Mountain, Anglesey.
- Parys Mountain, Anglesey: rancieite occurs as small (< 10 cm) stalactites within the Joint (45 fm.) level at Mynydd Parys as reported by Cotterell and Jenkins (2008).
There are no key localities for this specimen.
- Cotterell, T.F. & Jenkins, D.A., 2008. Ranciéite from Mynydd Parys, Amlwch, Anglesey, Wales. Journal of the Russell Society, 11, 59-63.
There are no references for this specimen.