This article explains why slate can be broken into large useful sheets, and also a little bit about how we can use those sheets in everyday life.
The cleavage of slate is the reason for its ability to be broken into large sheets. Rock cleavage refers to the planes that develop in in rocks where they can easily be split apart. Slate is formed from shale, which is a sedimentary rock formed by compressed layers of sediment. It then undergoes a transformation becoming a harder metamorphic rock. Although the rock has changed significantly, a low grade metamorphosis rock like slate still retains its layered structures which can then be seen as the cleavage. The rock can be split very easily along these cleavage lines.
In addition to the cleavage, the grain size of slate makes it ideal for splitting into sheets. The grain size determines the hardness of a rock. Having a fine grain size, slate is strong enough to be split into thinner layers without breaking and shattering too easily.
The natural propensity for slate to be easily broken into these sheets makes it an ideal choice for things like slate floors, walkways and counter tops. Slate has been most widely though for making roof shingles. Throughout the world people have been mining slate and finding that is makes a very durable and watertight roofing material. Due to its low water absorption, slate will not absorb water that can expand under cold conditions that can cause other materials to break. Slate is also good for outdoor walkways and floors, but be careful, the smooth slate can become very slippery!
So there you have it. Slate is easy to break along cleavage lines. The grain of the rock will make it possible to retain its thin sheets once split apart. These natural processes have made it an ideal material for many building purposes. For more information on the use of slate for floors, check out www.floors-web.com