After a significant period of prosperity in the 16th century, the devastation by Swedish troops in 1635 during the Thirty Years' War, along with geological factors, ended the mining activities in the Tellure site. In the 18th century, the discovery of cobalt ore revived the mines of the Val d'Argent region. The demand for this mineral, used to create blue color, was peaking for textile coloring and pottery decoration. A few dozen miners were still extracting cobalt around 1740, but serious flooding drowned some galleries, and the mines closed before the French Revolution.