Amgueddfa Cymru - National Museum Wales

Aeschynite

Crystal System: Orthorhombic
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Distribution: Rare
Chemical Composition: Rare earth-bearing titanium niobium oxide hydroxide
Chemical Formula: (Ce,La,Y,Ca,Fe,Th)(Ti,Nb)2(O,OH)6
Method(s) of Verification: backscatter energy dispersive X-ray analysis.

Chemical Group:

  • Niobates and Tantalates

Geological Context:

  • Igneous
Scanning electron micrograph of aeschynite (white) forming a minute grain in a thin veinlet cutting altered Ordovician intrusive rhyolite from Beddgelert Forest in central Snowdonia. British Geological Survey specimen KB474, © NERC.
Introduction: aeschynite is a group name, the individual member species being named on the basis of their rare earth element content, hence aeschynite-(Ce), aeschynite-(Nd) and so on. Aeschynite-(Y) is occasionally found in alkaline pegmatites in association with other rare-earth and niobium bearing minerals.
Occurrence in Wales: A small number of occurrences of aeschynite were noted by the British Geological Survey in Snowdonia during the 1980s and subsequently published by Howells et al. (1991). The material has not been fully characterized though the work done to date suggests that it is highly likely to be aeschynite-(Y).

Key Localities:

  • Snowdonia, Gwynedd: at three localities - Gallt Y Wenallt, Carnedd Y Cribiau and Beddgelert Forest - where altered Ordovician rhyolites outcrop. These carry microscopic veinlets in which small euhedral crystals of aeschynite occur (Howells et al., 1991). Intergrowths with Fe, Mn and Sc-rich Ti and Nb oxides are also present.

There are no key localities for this specimen.

References:

  1. 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.