Open-cast mining remained unchanged over time until the introduction of the gunpowder, in the 18th century, and the sinking of the Shaft of the Duke, the first underground salt mine, open between 1902 and 1905. Behind the new operation was the engineer Emilio Viader, who sought to exploit potassium salt in Cardona in the same way as at German sites.
After textiles, the discovery of potassium salt (1912) had resulted in the second industrialisation of Cardona. It doubled the population and produced significant transformations in its urban and social landscape. By September 1990 potash mining had ended. A total of 37,874,843 tons of mineral had been extracted from the earth and mining had reached a depth of 1,308.7 metres becoming the deepest mine in the country.