Heavy 3

Not all natural slates are equally durable. Heavy 3 can last over a hundred years, making it a very cost effective roofing material.
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 blue black 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.

Heavy 3 Natural Slates are available in the following sizes : 
30x20cm (12x8”) 
35x20cm (14x8”) 
40x20cm (16x8”) 
40x25cm (16x10”) 
50x25cm (20x10”)