Slate industry in Spain Slate industry in Spain 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. Slate is a fine-grained metamorphic rock that splits into thin, smooth-surfaced layers. Metamorphic rock is rock which was once igneous or sedimentary and has been subsequently subjected to heat and pressure in varying degrees thereby altering its composition, structure and appearance. It is used extensively in the building industry, particularly for roofing tiles. The production of slate is estimated at 4 million tons per year. Galicia is situated on the
Slate industry in Spain 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. Essentially, slate forms when the clay minerals in shale are put under increased pressure with high temperatures. The clay starts to revert to the mica minerals which cause the rock to grow hard with pronounced cleavage) directions. It is this cleavage which enables slate to be broken along flat, even planes. A large variety of colours and textures of slate can be produced, and the final