Crystal System: Orthorhombic
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Distribution: Rare
Chemical Composition: Calcium rare earth fluorocarbonate
Chemical Formula: Ca(Y,Ce,La,Nd)(CO3)2F
Method(s) of Verification: Beddgelert Forest - SEM EDX (Kearsley, Natural History Museum, unpublished data)

Chemical Group:

  • Carbonates

Geological Context:

  • Hydrothermal
  • Igneous
Introduction: synchysite-(Y) is limited in its occurrence to a relatively small number of paragenetic situations. It occurs in pegmatites, in carbonatites and in alpine fissure-type veins, where it is typically accompanied by other rare-earth element-bearing minerals and quartz, albite, the TiO2 polymorphs and chlorite.
Occurrence in Wales: the only record of synchysite-(Y) from Wales was cited by Bevins (1994), based on unpublished data provided by A.T. Kearsley. The occurrence, identified by energy-dispersive x-ray analysis, was in altered rhyolite in the Beddgelert district of Snowdonia. All other synchysites from Wales have been shown, by analyses, to be synchysite-(Ce) with only a minor yttrium content.

Key Localities:

  • Beddgelert Forest, Beddgelert, Gwynedd: radiating sheaves intergrown with quartz and K-feldspar in altered rhyolite (Bevins, 1994). No other details of this occurrence are known: however undifferentiated synchysite from rhyolite in Snowdonia, in similar habits and associations, is illustrated by Howells et al. (1991).

There are no key localities for this specimen.


  1. Bevins, R.E., 1994. A Mineralogy of Wales National Museum of Wales, Geological Series No. 16, Cardiff, 146pp.
  2. Howells, M.F., Reedman, A.J. & Campbell, S.D.G., 1991. Ordovician (Caradoc) marginal basin volcanism in Snowdonia (north-west Wales). HMSO for the British Geological Survey, 191pp.

There are no references for this specimen.