A naturally laminated rock, used in both regular and irregular shapes, and is embedded in cement or mortar to create a hard surface, patterned floor. It is graded in two categories: 1) clear stock which has no ribbons but has veining in the stone itself, and 2) ribbon stock which having bands of darker color running through it, is the less expensive of the two. In the application, the mortar bed is about 1/4" thick. On top of that, a mastic material is applied to about 1/8" thick. The slate flooring is then laid in the mastic. The slate flooring generally used for heavier-duty floors is between 1/2" and 1" and is set on a 1" mortar bed (either on a slab or wood floor system). When applied over wood floors, it is commonly applied over a felt and lath base.