At its heyday during the 19 th century slate from the quarries of north Wales was carried around the world and can be found covering the roofs of buildings on nearly every continent.
Yn ei anterth yn ystod y 19 eg ganrif, cafodd llechi o chwareli gogledd Cymru eu cario o amgylch y byd a gellir dod o hyd iddynt yn gorchuddio toeau adeiladau ar bron pob cyfandir.