Metamorphic Rocks

Slate was shale before it became metamorphoed. It is used for roof and floor tiles.

Marble was limestone before it became metamorphoed. It is used for building material.

Quartzite was sandstone before it became metamorphosed. It is used in road construction.

http://hyperphysics.phy-astr.gsu.edu/hbase/geophys/slate.html

http://blog.builddirect.com/slate

http://en.wikipedia.org/wiki/Marble

http://geology.csupomona.edu/alert/metamorphic/quartzite.htm

http://en.wikipedia.org/wiki/Quartzite