Today I found myself doing a bit of research on Boscawen-un stone circle near Penzance in Cornwall - much is written about it from Edward Thomas to John Michell.
Rupert Soskin (Standing With Stones) started his long and winding trip here - though it may have been the Merry Maidens, both circles have nineteen stones. Rupert intriguingly wondered if there was a connection betwween the Callenish lunar phenomenon of the eighteen and a half year cycle and the nineteen stone circles.
Boscawen-un also has a slanting central stone, however, one of the nineteen stones is quartz and I read somewhere that this was considered to be the 'healing stone'. Quartz is still considered to have healing 'energies' though this would probably fall down under scientific scrutiny.