The prevailing type of schist in the south-east of Anglesey, for some miles to the north and north-west of Beaumaris, is a wavily foliated, pale-green, chloritic rock, the quartz in which, though more abundant than appears at first glance, is in a very fine state of subdivision. In a common variety, especially prevalent about Llanddona, quartz forms nearly the whole of the rock, but it is still in very compact seams, separated by partings of chlorite or mica.