Slates are compact fine-grained metamorphic rocks, especially characterised by having a very homogeneous and penetrative foliation or schistosity, which allows them to be split into thin parallel smooth surface slices.
Originally these rocks started life as clay sediments deposited on ocean basins with other materials, becoming slates due to the effects of great pressure and temperature produced when the Earth’s plates collided and created the ancient mountain ranges.
Schistosity is a secondary characteristic which is due to the planar orientation of the principal minerals that make up these rocks, produced by the high tectonic pressures and metamorphism they have undergone.
The generic term Slates comprises a variety of rocks of very different appearance and composition, prevalent in the oldest geological formations (Precambrian and Palaeozoic). However, there are only a few ornamental slates of mining-industrial interest as construction materials. These must have certain intrinsic properties (mineral composition, hardness, flexibility, impermeability, durability, etc.) and must fulfill very special deposit conditions, as is the case with Villar del Rey.
The main surface characteristics of our slate are:
Intense black colour.
Very fine grain.
Very smooth uniform surface with fan-shaped vein.
No observable quartz veins or other negative features.
The mineralogical composition is mainly sericite (70%) and chlorite (15%) but also contains quartz, carbonaceous material, metal ores and other minerals.
The Villar del Rey slate has many uses. It is used for roofing, flooring, paving, cladding, walling, kitchen worktops, bathrooms and utensils for the hotel and catering industry.
Generally, the slate has a natural finish which is obtained after the exfoliation process. The rock has a smooth even surface, although the nature of the slate itself may result in small flakes being produced.
Slates designed for paving and exterior cladding normally have the same natural finish, but for flooring and interior cladding they can have a cut finish. This finish gives it a smoother surface than normal. It can also be waxed.
Slates for masonry do not have a special finish, only the one produced by cutting or sawing one or other face.