There is a book......
THE CAVES AND MINES OF ANGLESEY by Tony Oldham January 2006 ix + 57 pp, illus, surveys, 3 pages of colour photos. Anglesey is overshadowed by the great Parys Mountain copper mine. This book describes many of the smaller mines including the long forgotten coal mines at Berw. Usual gazetteer style: name, national grid reference, description and references. SB ?99.00 post free.