From the 1860s through the turn of the last century, five coal mining towns thrived in the Black Diamond area: Nortonville, Somersville, Stewartville, West Hartley, and Judsonville. As the location of California's largest coal mining operation, nearly four million tons of coal ("black diamonds") were removed from the earth. The residents of the mining towns were from all over the world, and their life was characterized by hard work and long hours. In the 1920s, underground mining for sand began near the deserted Nortonville and Somersville town sites. The Somersville mine supplied sand used in glass making by the Hazel-Atlas Glass Company in Oakland, while the Nortonville mine supplied the Columbia Steel Works with foundry (casting) sand.  The site is now a Regional Park. We will access the underground chambers for a guided look at the mining operations.  Lunch included.