These cookies are absolutely essential for our website to function properly.
We use Google Analytics to measure how you use the website so we can improve it based on user needs.
These cookies may be set by third party websites and do things like measure how you view YouTube videos.
Scanning electron micrograph of sheaf-like aggregate of prismatic cymrite from Benallt Mine. National Museum of Wales specimen (NMW 2006.15G.M.2), © National Museum of Wales.
Cream coloured pseudohexagonal cymrite crystals to 1 mm across from Benallt Mine. D.I. Green photo, © D.I. Green.
cymrite is roughly equivalent to hydrated celsian and appears to form in barium-rich rocks under conditions of low grade metamorphism. Experimental work suggests that it forms from baryte under alkaline conditions and breaks down to celsian and water at around 300°C and 3 kb (or lower temperatures at low pressure) (Hsu, 1994).
cymrite was first described from Benallt Mine, near Rhiw, Llŷn, North Wales (Campbell Smith et al., 1949) and this locality remains the only known Welsh occurrence of the mineral. Campell Smith et al. (1949) examined material collected by A.W. Groves, who had recently surveyed the mines, but only minute amount of cymrite were present, such that two specimens, from different locations in the mine, were required to characterize fully the new mineral. This type material is held in the Natural History Museum (B.M. 1944, 36 and B.M.1944, 48).