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Cymraeg

Rosasite

Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Copper zinc carbonate hydroxide
Chemical Formula: (Cu,Zn)2(CO3)(OH)2
Method(s) of Verification: Frongoch Mine - XRD (Green et al., 1996); Gwaith-yr-afon Mine - XRD (NHM); Hendy Quarry - IR (Plant, 1993); Henfwlch Mine - XRD & EPMA (NMW X-1269); Locks Common - visual; Machen Quarry - IR (Plant & Jones, 1995), XRD (NMW X-911 & X-913)

Geological Context:

Globular aggregates of rosasite from Machen Quarry. I.E. Jones Collection. © National Museum of Wales.
Introduction: rosasite is a secondary carbonate formed as a result of oxidation of primary copper- and zinc-bearing minerals. Hemimorphite and aurichalcite are typically found in association with rosasite.
Occurrence in Wales: rosasite was first recorded in Wales by Fletcher & Young (1988) from calcite-lined vughs in Carboniferous Limestone at Bute Quarry, near Llantrisant and from a borehole at Locks Common, near Porthcawl in South Wales. These occurrences are both considered unconfirmed given the descriptions made, in particular, when the analytical results are carefully considered. It seems most likely that both cases are in fact zincian malachite with highly variable proportions of zinc. However, rosasite is likely to occur at Bute Quarry, as it has been identified from the neighbouring Hendy Quarry (Plant, 1993) where, it forms small bluish-green radiating spherules on calcite. At Machen Quarry, also in South Wales, rosasite is locally common. Blue-green spheroidal and botryoidal aggregates occur associated with altered chalcopyrite within barite-dominated veins. Further north, rosasite is present in small quantities in the Central Wales Orefield. Confirmed occurrences include, Gwaith-yr-Afon (Rust & Mason, 1994) Frongoch (Green et al., 1996) and Henfwlch mines (T.F. Cotterell, unpublished data), while rosasite is thought to be present at Eaglebrook Mine (National Museum of Wales Collection).

Key Localities:

There are no key localities for this specimen.

References:

  1. Bevins, R.E., 1994. A Mineralogy of Wales National Museum of Wales, Geological Series No. 16, Cardiff, 146pp.
  2. Dana, J.D., Dana, E.S & Palache, C., 1952. A System of Mineralogy. 7th Edition, Vol. 2. New York, John Wiley, 1124p.
  3. Fletcher, C.J.N. & Young, B.R., 1988. Rosasite from Bute Quarry, Mid Glamorgan. The first reported occurrence in Wales. Journal of the Russell Society, 2(1), 19-23.
  4. Green, D.I., Rust, S.A. & Mason, J.S., 1996. Classic British mineral localities: Frongoch Mine, Dyfed. UK Journal of Mines & Minerals, 17, 29-38.
  5. Jambor, J.L., 1976. Studies of basic copper and zinc carbonates: three powder X-ray data for zincian malachite, rosasite, and cobalt analogues. Rept. of Activities, Part C, Geological Survey of Canada, Paper 76-1C, 97-105.
  6. Jones, A.D., 1983. Nant-y-Cagl. Mineral Realm, 3, 42-76.
  7. Plant, S., 1993. Rosasite from Hendy Quarry, Miskin, South Wales. British Micromount Society Newsletter, 35, 8.
  8. Plant, S.P. & Jones, I.E., 1995. Minerals of Machen Quarry, Mid Glamorgan, Wales. Journal of the Russell Society, 6(1), 31-36.
  9. Rust, S.A. & Mason, J.S., 1994. An unusual occurrence of arsenate minerals at Gwaith-yr-Afon mine, Dyfed, Wales. Journal of the Russell Society, 5(2), 109-113.

There are no references for this specimen.