Black Diamond Mines Regional Preserve

Black Diamond Mines Regional Preserve is a roughly 6,000-acre park in Contra Costa County, California, administered by the East Bay Regional Park District, which took ownership of the property in 1973. Its historical significance stems from coal and sand mining operations that once supported multiple communities here — remnants of three former mining towns are preserved within its boundaries.

Visitors today can explore those townsite relics and, notably, take guided tours of a former sand mine. About 60 miles of trails wind through rolling foothill grasslands and California oak woodland, making the preserve as much a hiking destination as a heritage site. The landscape sits north of Mount Diablo, giving the terrain a characteristic open, hilly character.

Access is managed by the East Bay Regional Park District, so checking current tour schedules and park hours before visiting is worthwhile. The oak-and-grassland setting is best enjoyed in spring when hills are green, though summer and fall visits are equally practical. Winter months can bring wet, muddy trail conditions across the rolling terrain.