Slate is a fine grained metamorphic stone formed from clay mud; composed of sediments of decomposed stone and organic matter that has been hardened by heat and pressure. Since the geological process varies greatly, slates range quite a bit in hardness and porosity. Slate is very durable and water repellent as well as acid, frost, stain and fire resistant. It's near perfect horizontal splitting plane makes Slate an extremely practical finishing material.

Slates have wide ranging physical characteristics and overall suitability. It differs in density, tensile strength, and absorbency and abrasion resistance.