Mexico’s second-richest man has added $1.3 billion to his net worth this year, buoyed by a surge at Industrias Penoles SAB and Fresnillo Plc, owner of the world’s largest silver mine.

Located 260 km away from Durango city, in northern Mexico, the Guanacevi mine, which Endeavour acquired in 2004, is the company’s highest-grade silver operation. The mine produced 4.3 million oz ...