Hazel Atlas Mine underground visitor center.

Sand Mine Underground Visitor Center

Pittsburg, California

Call us provincial, but we'd never heard of an underground sand mine before (most sand mining is conducted above ground or in pits). Someone was thoughtful enough to create a museum within the tunnels of a retired silica-sand mine -- in the Black Diamond Mines Regional Preserve northeast of San Francisco. The Greathouse Visitor Center in the Hazel-Atlas Mine is deep in a mountainside; once we reached the entrance portal from our car, it was a level walk in steadily cool 56 F degree passageways.

Greathouse Portal to visitor center.

The exhibits cover the 19th century coal and 20th century sand mining eras. High quality silica-sand was extracted from the hill's sandstone layers, processed elsewhere, and used for regional glass and steel foundry manufacturing. The activity lasted from the 1920s to 1949, when the last mine closed.

A 950 ft. corridor has been restored to how it might have looked when operating in the 1940s. The first set of exhibits are self-guided (dogs permitted); a larger area of the Greathouse and the Hazel-Atlas workings (entered through a second outside portal) can be seen on 90-minute long guided tours (no dogs).

Sure, it lacks some of the romance of a gold or silver mine, but it was dangerous work. Let's not forget the bravery of America's gritty-toothed sand miners.

The picturesque Black Diamond Mines Regional Preserve offers other historical sites for hikers and wanderers -- meager remnants of mining ghost towns and blown up mine shafts, usually noted with an informative used-to-be-here sign.