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 product depends largely on the tectonic environment, the source of the sedimentary material, and the physical/chemical conditions prevalent during the sedimentation process. As the sedimentary deposits were compacted, water was squeezed out, hence turning clay minerals into mica, and then solid mudstone. The subsequent mountain building compaction which occurred over the next few million years resulted in an even stronger rearrangement and planar orientation of the minerals. This means that in true slate the cleavage plane is very different from the original bedding plane and led to the well developed cleavage for which the region is famous. The Galician slate