Why Choose Slate
Spanish slate is elegant, versatile and natural. Characterised by colour and texture, natural slate will enhance the style and beauty of any property. Primera specialise in the sale of Spanish slate, from premium quarries, where the largest reserves of tectonic natural slate throughout the world can be found.
Slate is characterised by natural colour, with variations across quarries, one of the most versatile natural materials on earth. Slate is hand crafted and is able to be used immediately upon its mining. There are no treatments necessary. With slates as perfect as they are from the Primera supply chain, homes and properties are guaranteed to be enhanced by the addition of Primera roofing slate, when used in architecture or design, slate is timeless, elegant and adaptable.
The texture of slate tells a story of its history. Slate is a fine-grained, foliated, homogeneous rock which came from an original shale-type sedimentary rock composed of clay or volcanic ash through regional metamorphism. Foliation, in terms of geology, refers to repetitive layering in the creation of metamorphic rocks. The layers may be as thin as a sheet of paper or up to a meter thick. The layering is caused by shearing forces- pressures pushing sections of the rock in different directions, or differential pressure- where higher pressure is placed on one area than another.
The foliation in slate is called ‘salty cleavage’ where strong compression causes fine grained clay flakes to grow in planes perpendicular to the direction that the pressure is being applied.
When struck parallel to the foliation, the slate will display a property called fissility- where smooth sheets are produced- these are the tiles with which roofs, floors and other surfaces are covered.
Slate is mainly made from quartz and muscovite or illite, often along with biotite, hematite and pyrite. The vast majority- over 90%, of European natural slate used for roofing originates from the slate quarries of Spain. The region of Galicia is the primary production area. The area is synonymous with slate because this Northern region of Spain has been subjected to periods of magmatic activity with volcanos erupting, pouring molten rock over the ground. Some of the region’s slate deposits date back over 500 million years.
The varying colours and textures of slate depend upon the tectonic environment, the material that originally made the compound, sedimentary material and the physical or chemical conditions that existed during the sedimentation process. As the deposits are compounded, water is squeezed out. The clay minerals are turned into mica and then into solid mudstone. In highest quality slate, the cleavage plane is very different to the bedding plane. Northern Spain has the perfect mineral, chemical and physical balance, leading to the well-developed cleavage and the exceptional conditions which create the region’s world-renowned slate.