Monterey Trip #10
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Monterey & Northern California #10

Mount Diablo Coal Field

From 1860 to 1906, this area was the largest coal mining district in California. Five
towns (Nortonville, Somersville, Stewartville, Judsonville, and West Hartley) grew
up around twelve major mines.  Today the towns are gone and the buildings have
been moved to nearby communities.  Mine openings, tailings, railroad beds, and a
pioneer cemetery are being preserved by the East Bay Regional Park District. This
historic area is now designated California Registered Historical Landmark No. 932.

Entrance to the Black Diamond Coal Mine at Somersville.

Coal From The Black Diamond Mine at Somersville

These coal fragments collected from mine tailings are a type of coal known as lignite. They were formed from partially decayed plant matter under heat and pressure over millions of years. Higher grades of coal include dark bituminous coal with a dull luster, and hard, black anthrocite coal with a metallic luster. Jet is a hard, shiny black material derived from the metamorphosis and anaerobic fossilization of conifer wood buried under sediments in ancient seas. Chemically, jet it is a hard, carbonized form of bituminous coal with a density similar to anthracite coal. Jet takes a high polish and has been used for shiny black jewelry for thousands of years.

See Images Of Jet From Northern England

Burning lignite coal from the Black Diamond Mines near Somersville

A piece of lignite coal ignited with a propane torch. Lignite has a heating value of 7,400 British Thermal Units (B.T.U.) compared with 9,700 to 15,400 B.T.U. for bituminous coal. Black Diamond Coal from the California Coast Ranges of Contra Costa County fueled the rapidly expanding urban and industrial centers of the San Francisco Bay area during the early 19th Century. Between 1860 and the early 1900s, four million tons of coal were taken from the Black Diamond mines.

Pit stop at the Black Diamond Coal Mine at Somersville. This outhouse is not
 an historic building from the original Black Diamond Mines of the late 1800's.

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