Slate is a metamorphic stone. It is usually quite fine grained and can be found in basic grays, greens and blacks. Also, more exotic color ranges exist that bring to a space a uniqueness of spirit rarely found elsewhere. Slate slabs yield exquisitely interesting kitchen and bath tops.
Per Wikipedia “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. It is the finest grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression