Black Diamond Mines Regional Preserve

The Black Diamond Mines Regional Preserve is a 6,000-acre (2,400 ha) park located north of Mount Diablo in Contra Costa County, California under the administration of the East Bay Regional Park District. The 60 miles of trails in the Preserve cross rolling foothill terrain covered with grassland, California oak woodland, California mixed evergreen forest, and chaparral. The trails offer views of Mount Diablo, the Sacramento-San Joaquin River Delta, and on clear days, the Sierra Nevada.

The Preserve usually has an impressive variety of wildflowers in spring including the rare Mount Diablo fairy lantern (Calochortus pulchellus), Mount Diablo sunflower (Helianthella castanea), and Brewer's dwarf flax (Hesperolinon breweri). It is home to a variety of wildlife including deer, mountain lions, coyotes, foxes, bobcats, golden eagles, and a variety of hawks. The endangered San Joaquin kit fox (Vulpes macrotis mutica) and threatened California red-legged frog (Rana draytonii), California tiger salamander (Ambystoma californiense) and Alameda whipsnake (Masticophis lateralis) are present as well. The park is open year-round for hiking, mountain biking, and horseback riding from 8 am to dusk. A backpack camp and a group camp can be reserved for overnight stays.

From 1860 to 1906, the area was known as the Mount Diablo Coalfield, the largest in California. The area includes the remains of twelve coal mines and the sites of five long-gone coal mining towns. The Preserve contains over 200 miles of mine workings. The largest and oldest town, Nortonville, had a peak population of about 1,000. Somersville, Stewartville, West Hartley and Judsonville were located in valleys to the east. The mines were the Empire, Central, Star, Corcoran, Pittsburg, Manhattan, Eureka, Independent, Union, Black Diamond, Mt. Hope, and Cumberland. The four million tons of coal produced was of a low grade (sub-bituminous or lignite), but for a time in the 19th century, was the only readily accessible and economic source in California. The coal was carried to the San Joaquin River by three railroads (the Empire, Pittsburg, and Black Diamond and shipped by barge to markets in the San Francisco Bay Area, Sacramento, California, Stockton, California and other communities.

Coal mining activity ended as better-quality imported coal became affordable and as petroleum emerged as an energy source. After the coal mines closed, the towns were abandoned and the area was used mainly for cattle grazing. Rose Hill Cemetery, the final resting place for over 200 residents of the coalfield, is located on a hillside between the Somersville and Nortonville townsites. Many of the burials were for children who died in epidemics of scarlet fever, typhoid fever, smallpox, and diphtheria. Many of the gravestones have been stolen or destroyed by vandals. The coal mines are closed due to hazards posed by the age of the mines, the gases they produce (carbon dioxide and methane), and their rock quality (the shale and coal in the mines is unstable). However, a number of mine openings have been turned into public-access openings which allow visitors to look into the mines and, for some, to walk a short distance underground. The deepest public-access opening is known as Prospect Tunnel. Visitors can enter 200 feet of this excavation made by miners searching for coal.