Slate is commonly gray in color, although you may find green, yellow and red hues. It is a material from metamorphosed state. That is, it consists of clay like materials that have undergone change under heat and pressure. Slate can be recognized by its sheet-like structure. The material is usually thin, and if broken, will flake off into sheets. Slate rarely is highly reflective, unless a coating is placed on top of it. Its surface is usually uneven, unless machine sanded. Slate is also prone to detonation around water areas.