Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence
Distribution: Locally Abundant
Chemical Composition: Sodium calcium magnesium iron titanium aluminium silicate hydroxide
Chemical Formula: NaCa2(Mg,Fe2+Fe3+)4Ti(Si6Al2)O22(OH)2
Method(s) of Verification: Tal y Fan - EMPA (Merriman et al., 1986).
Introduction: kaersutite is a titanium-rich (with up to 6 weight % TiO2) calcic amphibole. It is characterisitc of camptonite (an igneous rock rich in iron and magnesium minerals) and also some basic, alkaline igneous rocks.
Occurrence in Wales: there are two confirmed occurrences of kaersutite from Wales (Merriman et al., 1986; Bevins, 1979).
- Llanwnda, Pembrokeshire: kaersutite occurs as a minor component in Ordovician dolerite and gabbroic intrusions in north Pembrokeshire. For example the Llanwnda Intrusion, exposed to the west of Fishguard, contains kaersutite associated with chlorite; suggesting that it formed under late-stage magmatic conditions (Bevins, 1979).
- Tal y Fan, Conway: kaersutite forms small, strongly pleochroic crystals in the central zone of the Tal y Fan Intrusion, Gwynedd (Merriman et al., 1986).
- Bevins, R.E., 1979. The geology of the Strumble Head-Fishguard region, Dyfed, Wales. Unpublished Ph.D. thesis, University of Keele, 256pp.
- Merriman, R. J., Bevins, R.E. & Ball, T.K., 1986. Petrology and geochemical variation within the Tal y Fan Intrusion: a study of element mobility during low-grade metamorphism with implications for petro-tectonic modelling. Journal of Petrology, 27, 1409-1436.