This rock consists chiefly of clay minerals with subsidiary amounts of quartz and mica. This foliated rock is the metamorphic product of chiefly clay-rich sediments, exhibiting a characteristic cleavage.
Slate is a fine-grained, foliated, homogeneous, metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low grade regional metamorphism. The result is a foliated rock in which the foliation may not correspond to the original sedimentary layering.
Slate is frequently grey in colour especially when seen en masse covering roofs. However, slate occurs in a variety of colours even from a single locality.