The slate industry is the industry related to the extraction and processing of slate. Slate is either quarried from a slate quarry or reached by tunneling in a slate mine. Common uses for slate include as a roofing material, a flooring material, gravestones and memorial tablets, and for electrical insulation.

Slate is a fine-grained metamorphic rock that splits into thin, smooth-surfaced layers. Metamorphic rock is rock which has changed from one form of matter into another and is not as was originally laid down by nature. It is used extensively in the building industry, particularly for roofing tiles. The production of slate is estimated at 4 million tons per year.

90% of Europes's natural slate used for roofing originates from the slate industry in Spain, with the region of Galicia being the primary source of production.

The Northern region of Spain has been subjected to periods of magmatic activity with volcanism, and this has led to the region’s unique geological development in respect of slate.

Slate deposits are over 500 million years old, having been formed during the Cambrian, Ordovician and Silurian periods of the Palaeozoic era.

Bibliography: http://en.wikipedia.org/wiki/Slate_Industry_in_Spain