slate
slate

The slate, is commonly known in Portugal as a "blackboard ". It is a homogeneous rock, very thin, opaque grain, resistant and can easily be separated or riven into parallel sheets if worked in the cleavage sense.

It originates from complex argillaceous sediments, usually from the weathering of rocks and other sources, where a more or less deep metamorphosis has been developed.

Its composition mainly clay minerals and laminar mica, gives it a smooth structure and a typical peeling sheets (foliation), which becomes a very suitable material for roof tiles to perform covers.

Over the time the slate has been used in roofing, wall coverings and flooring, sometimes in rustic traditional houses as well as in noble and religious architecture .