The information below on slate sites in the Galicia and León regions is taken frorn a study carried out by the Instituto Geologico-Minero de España. Ten areas have working quarries and known reserves: Valdeorras, La Cabrera, A Terra Chá, Monte Rande, Los Oscos, Aliste, Bernardos and Villar del Rey.
This area of the province of Orense has the country’s heaviest concentration of slate works. It is the area which is most widely known and is home to most of the companies working in the field.
Most, though not all, of the quairies are concentrated in Casayo, Castañairo, Rozadais, Los Molinos, Castrelos, Los Campos, Pedriña, Domiz, Penedo and San Vicente.
Slate from the same level of strata shares the same characteristics, but differences can be seen between sites and even within single sites due to slight variations in composition, the relationship of schistosity to stratification, secondary tectonic factors, etc. The specialists distinguish between the most common types from each area and consider them as different varieties of roofing slate. Their suitability and quality have been proved by experience.
The reserves of this area are practically limitless, and apart from the sites already being worked others could be opened up. Several open cast sites are worked on a large scale, and at others work is just beginning and new fronts are being opened up.
This mountainous region, in the province of León, borders on Valdeorras and is similar to it in geographical and geological characteristics. It already has large slate-works, and others are starting up with the expectation of large output. The workable slate levels are the same as for Valdeorras, and the viability of the sites depends on the same general and local factors.
This central area of Lugo owes its name to its gentle landscapes. The municipalities of Mondoñedo, Lorenzana, Pastoriza and Pol contain several sites which work the area’s peculiar green slate. All the area’s works produce the same type of slate, known as Verde Lugo [«Lugo Green»], though a small amount of greyer slate is also produced. The reserves of this slate are geologically limitless,
though the lie of the land makes it hard to discover new sites.
Monte Rande, in the municipal area of Ortigueira in the north of La CoruñA province, has several large, high-production slate works. At the present rate of production its reserves are also very great. A feature of the slate from this area is the consistently large size of the sheets produced.
This area is on the border between the provinces of Lugo and Asturias.
It contains a large works at Villarchao (Lugo) and other craftsman-type sites. As might be expected, the slate reserves are not as high as in the above areas, but they are nevertheless sufficient to guarantee the survival of the existing works and allow one or two more to be opened up in the future.
The slate produced at Villarchao is one of the most characteristic slates in the area. It is of high quality, and can generally be cleaved into large sheets.
The valley of the River Aliste in the west of Zamora province has severaL roofing slate works, including some of considerable size. The workable levels are thick layers of black and grey slate. The scale of the area’s reserves has yet to be determined, and may be very large.
Close to the town of Bernardos in the province of Segovia there are two well-known slate orks. Most of their output is used for paving slabs and decorative claddings, but they also make roofing slate when the market requests it and when the layers worked permit.
Near Villar del Rey in northern Badajoz province there is a well-known roofing slate site. The slate reserves of this area are limited, but still sufficient to supply the existing works and any others which might be opened up in future for a long time.
Source: Centro Tecnológico de la Pizarra de Galicia