From the 1920s to the ’40s, the Hazel-Atlas Mine at Antioch’s Black Diamond Mines Regional Preserve served as a rich source of silica sand for the manufacture of jars, bottles and other glass items.

The park conducts 90-minute tours of the mine on weekends at noon and 3 p.m. March through November. The tour takes visitors along a 950-foot stretch featuring mine workings, ore chutes and ancient geological features. The fee is $5; tickets can be purchased at the Sidney Flat Visitor Center. Weekday tours for groups of 10 or more can be reserved by calling 510-544-2750.

Since the tours are filled on a first-come, first-served basis, tour participants should arrive at least one hour early to provide time to get to the mine entrance and ensure a spot on the tour. For more information, visit www.ebparks.org/parks/black_diamond.