They are found in Skye , Mull , Antrim and other places , where there are Paleogene volcanic rocks ; in Scotland , Derbyshire and Ireland among the carboniferous strata ; and among the still older rocks of the Lake District , southern uplands of Scotland and Wales .
They are found in Skye , Mull , Antrim and other places , where there are tertiary volcanic rocks ; in Scotland , Derbyshire and Ireland among the carboniferous strata ; and among the still older rocks of the Lake District , southern uplands of Scotland and Wales .