Rocks are naturally occurring solids which are composed of minerals & have been used by humans since ages. From Stone Age, rocks are used for various purposes. Also, the metals and minerals found in rock play an important role in our life. Get to know all the Slate Uses. We have provided you with all information about Slate rock here. 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. Slate is available in black, brown, buff, green, light to dark grey, purple, red, shades of blue colors. The streak of a rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Slate is light to dark brown. Get to know more about Slate rock and characteristics of Slate rock in the next sections.