Crystal System: Hexagonal
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Aluminium sulphate hydroxide hydrate
Chemical Formula: Al4(SO4)(OH)10.5H2O
Method(s) of Verification: Moel Goedog - XRD & DTA analysis; Parys Mountain - XRD.

Chemical Group:

  • Sulphates

Geological Context:

  • Supergene: in situ natural oxidation & weathering deposits
Introduction: a secondary mineral formed by the dehydration of hydrobasaluminite under weathering conditions.
Occurrence in Wales: Ball (1969) provided the first account of basaluminite from Wales from shattered black shales of the Clogau Group, exposed on a hillside near Harlech. More recently, investigations into the post-mining mineralogy of Parys Mountain have produced a second account of basaluminite in Wales.

Key Localities:

  • Moel Goedog, near Harlech, Gwynedd: Ball (1969) described a single cavity (c. 2 x 1 cm diameter) in black shale, filled with a white earthy mineral which was subsequently shown to be basaluminite, from a small roadside pit on the slopes of Moel Goedog.
  • Parys Mountain, Anglesey: basaluminite, from this locality, was listed without description by Jenkins et al. (2000).


  1. Ball, D.F., 1969. Basaluminite from Cambrian rocks near Harlech. Mineralogical Magazine, 37, 291-293.
  2. 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.