Black Diamond Mines Regional Preserve
The Black Diamond Mines Regional Preserve is a 6,000acre (2,400 ha) park loed north of Mount Diablo in Contra Costa County, California under the administration of the East Bay Regional Park District (EBRPD). The district acquired the property in 1973. The preserve contains relics of 3 mining towns, former coal and sand mines, and offers guided tours of a former sand mine.