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Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence
Distribution: Locally Abundant
Chemical Composition: Zinc carbonate hydroxide
Chemical Formula: Zn5(CO3)2(OH)6
Method(s) of Verification: All by XRD: Castell Mine (NHM, 4672F); Cwmleyshon Quarry (NHM, 2979F); Dylife Mine (NHM, x13803 & 1600F); Esgair Hir Mine (NHM, 6789F); Machen Quarry (NMW X-840 & X-910); Parc Mine (NHM, 4881F); Van Mine (NHM, 1613F); Gwaithgoch Mine (NMW X-1527).

Geological Context:

Post-mining hydrozincite flowstone from No. 3 Level, Parc Mine, Llanrwst, Gwynedd. Specimen 11.5 cm across. National Museum of Wales Collection (NMW 85.70G.M.29) ex R.W. Barstow Collection. © National Museum of Wales.
Post-mining hydrozincite flowstone developed on wood from underground workings at Van Mine, Central Wales Orefield. National Museum of Wales Collection (NMW 27.111.GR.14) ex G.J. Williams Coll. Photo T.F. Cotterell, © NMW.
Introduction: hydrozincite is a common secondary carbonate mineral which forms typically as post-mining flowstone, on mine walls associated with zinc orebodies, particularly those containing sphalerite.
Occurrence in Wales: traces of hydrozincite are present at most localities where sphalerite has been subjected to weathering, particularly within mine dumps, but the more spectacular occurrences occur where hydrozincite has precipitated as flowstone within underground mine workings. Large masses of brilliant white flowstone have been collected over the years from both working and abandoned zinc mines across the Principality. G.J. Williams, the former H.M. Mine Inspector for North Wales, collected fine large specimens of hydrozincite from many of the working mines during the early 20th Century including Van, Parc and Aberllyn. Hydrozincite occurs in some degree or another at most of the mines in the Central Wales and Llanrwst Orefields. The richest specimens have been found in underground workings where, precipitation of hydrozincite is frequently ongoing. Modern discoveries of this nature have been made at Bwlch-glas, Gwaithgoch and Cwmystwyth mines in the Central Wales Orefield and also at Castell Carn Dochan Mine near Bala in Gwynedd. Somewhat surprisingly given the abundance of sphalerite in Flintshire, hydrozincite is only recorded in traces, usually dump-formed. It appears that conditions are preferentially suited to the development of the zinc carbonate smithsonite instead. In South Wales, traces of hydrozincite occur, occasionally coating sphalerite crystals within ironstone nodules in the South Wales Coalfield, but by far the richest samples are to be found in the dolomitic limestone quarries near Machen. At Machen Quarry, hydrozincite forms massive white powdery patches within the upper reaches of barite veins containing altered primary galena, sphalerite and chalcopyrite. Similar material is present at the nearby Cwmleyshon Quarry.

Key Localities:


  1. Alwan, A.K. & Williams, P.A., 1979. Nickeloan hydrozincite: a new variety. Mineralogical Magazine, 43, 397-398.
  2. Bevins, R.E. & Mason, J.S., 1998. Welsh Metallophyte and metallogenic evaluation project: Results of a Minesite Survey of Gwynedd. National Museums of Wales, Cardiff.
  3. Bevins, R.E. & Mason, J.S., 1997. Welsh metallophyte and metallogenic evaluation project: Results of a minesite survey of Dyfed and Powys. CCW Contract Science Report No. 156. National Museums & Galleries of Wales.
  4. Bevins, R.E. & Mason, J.S., 1999. Welsh Metallophyte and metallogenic evaluation project: Results of a Minesite Survey of Clwyd. National Museums & Galleries of Wales, Cardiff.
  5. Bevins, R.E., O’Brien, P., Turgoose, S., & Williams, P.A., 1982. A New find of nickeloan hyrozincite in the Parc Mine, North Wales. Journal of the Russell Society, 1, 19-21.
  6. Bevins, R.E., Turgoose, S., & Williams, P.A., 1982a. Namuwite, (Zn,Cu)4SO4(OH)6.4H2O, a new mineral from Wales. Mineralogical Magazine, 46, 51-54.
  7. Jones, J.A. & Moreton, N.J.M., 1977. The Mines and Minerals of Mid-Wales 40pp.
  8. Plant, S.P. & Jones, I.E., 1995. Minerals of Machen Quarry, Mid Glamorgan, Wales. Journal of the Russell Society, 6(1), 31-36.