Crystal System: Hexagonal
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Distribution: Locally Abundant
Chemical Composition: Calcium phosphate carbonate hydroxide
Chemical Formula: Ca5(PO4,CO3)3(OH,F,O)
Method(s) of Verification: none.

Chemical Group:

  • Phosphates

Geological Context:

  • Sedimentary: diagenetic
Introduction: carbonate-hydroxylapatite, is also known as dahlite.
Occurrence in Wales: Oakley (1934) reported the occurrence of dahlite at Tŷ Mawr, Rumney, South Wales. This account represents the first record of this mineral in the British Isles. More recently Niedermeyer & Langbein (1989) have shown that bacteriogenic pebble coatings (co-called 'bolopora') which occur in rocks of Arenig age over a wide area of Wales, are composed of carbonate-hydroxylapatite.

Key Localities:

  • Tŷ Mawr, Rumney, South Wales: pearl-like bodies in cells of fossil corals from Silurian strata, where identified as carbonate-hydroxylapatite by Oakley (1934).


  1. Niedermeyer, R.-O. & Langbein, R., 1989. Probable microbial origin of Ordovician (Arenig) phosphatic pebble coats ('Bolopora') from North Wales, U.K. Geological Magazine, 126, 691-698.
  2. Oakley, K.P., 1934. Phosphatic calculi in Silurian Polyzoa. Proceedings of the Royal Society of London, Series B, 116, 296-314.