Slate Slate has an excellent shining property. Slate is a popular ornamental and decorative stone because of the pleasing colors, attractive patterns and designs. Slate tiles are used for wall cladding, roofing and flooring. Slate is suitable for Exterior and Interior Applications. Slate is a very fine grained metamorphic rock derived from the sedimentary rock 'shale'. Slate is composed mostly of mica, chlorite and quartz. Characteristically the rock may slit into relatively thinner slabs and can break easily.