Slate

Slate is a fine-grained, metamorphic stone derived from sedimentary rock shale.  It consists mainly of grains of mica, chlorite, and quartz and may also have calcite, pyrite, hematite, and other minerals.  Most slate is gray to black in color, but the rock can come in shades such as dark to light green, mottled purple, black, gray or dark red depending on its mineral content.  Unless its surface has been honed smooth, slate can be recognized by its distinct cleft pattern.  Slate is commonly used for roofing and flagstones because it is weatherproof and long-lasting.  Slate can also be used to trim building lobbies, pool tables, counter tops, tabletops and fireplace facing.