If you subject shale, a sedimentary rock, to heat and pressure you will get a rock called slate.  Slate is a flat rock that comes in shades of gray or gray-green.  It is very hard, dense and fine grained.  Because it is easy to split along flat planes it is often used to make floors, terraces, or garden steps.

More about metamorphic rocks including slate

Warning!   The vocabulary on this web site is difficult.

Slate Museum Home Page