Natural slate: Heavy 3
Cupa Heavy 3 slate is quarried from the CUPA PIZARRAS No3 quarry in San Pedro de Trones (León) in northern Spain. This quarry has been in operation since 1892 and produces around 25,000 tonnes each year.
The slate is dark-grey with a slightly gritty texture, and in some samples well defined parallel lines are clearly visible on the cleavage surfaces.
Slate from San Pedro quarry is produced in two thicknesses, 3.5mm and 7-8mm; the thicker variant being the preferred choice in Scotland. The extra thickness and weight give it strength to withstand the high wind speeds and driving rain common throughout Scotland.
No slate is a true match for Ballachulish, the bestknown of Scottish slates. However there are many similarities between Ballachulish and our Heavy 3. Both are blue-grey in colour and have similar thickness, and pyrite crystals are usually present in both. In the absence of a new source of Scottish slate, Heavy 3 is the best choice for repair and replacement of traditional roofs in Scotland.