This is (multi-colour slate), which was formed under very high pressure and relative low temperature. Stone is very hard, contains besides clay derived crystals also quite some Ferro-hydroxides. The latter can become oxidized further to form hematite with its spectacular range of colours. This stone must be selected from layers deeper in the mountain, as oxidation near the surface may cause swelling in the stone, so it becomes too soft for many applications. Normal sizes are 30/60 and some 60/60, but the latter is often difficult due to curving of the tiles. Stone is popular for cladding, strips and can be used in and outdoors, even driveways have been made from it.