Slate is one of the most common roofing materials, is also often found as a building material too. Slate is easily split into thin sheets and has a natural resistance to water. Usually slate is grey in colour, however Cumbrian and Welsh slate often has a purple or green hue.
Also, slate tiles, being a natural product do not have the perfectly flat surface which porcelain tiles have unless they are polished. However this naturally uneven surface is part of each tiles' charm.
As mentioned, natural slate can be polished to give a perfectly flat surface, but for me, this not only defeats the object of having a natural slate floor, but also drives the price up considerably. If you want slate flooring without the uneven surface, you could consider porcelain tiles instead. And before you say porcelain is nothing like slate, think again. Porcelain can be manufactured to mimic many natural types of stone, and slate is no exception.
The natural slate is a metamorphic rock derived from sedimentary rock it is built up of many very thin but separate layers. It is this characteristic which makes slate so easy to split into sheets which feature a relatively flat, but slightly uneven surface. These cleft planes can 'spall', or flake and occasionally this can become problematic. However porcelain tiles which are made to look like slate tiles do not have these natural cleft planes and therefore will not spall.
Porcelain can give the best of both worlds and is a fair compromise if you want the look of slate without the 'randomness' of its hue or surface contours. Porcelain is also easier to keep clean and is often less costly than natural tiles. Saying that, it doesn't quite feel the same under foot as natural slate does.
Source: Carl Live, Ezine Articles