Near Ornon, the route regularly unveils slate deposits. These black rock sheets are commonplace here. Slate was for a long time mined, providing a certain amount of prosperity to the village. A century ago, 9 quarries employed 250 people. The slate was used for roofs, but their quality was much in demand, and sometimes was exported. The quarries were worked in the winter, since the workers were farmers the rest of the year. Industrial materials began to compete with natural slate, and mining came to a halt in about 1950.