From the 1860s through the turn of the last century, five coal
mining towns thrived in the Black Diamond area: Nortonville,
Somersville, Stewartville, West Hartley and Judsonville. As the
location of California's largest coal mining operation, nearly four
million tons of coal ("black diamonds") were removed from the
earth. By the time operations ceased due to rising production costs
and the exploitation of new energy sources, much of California's
economy had been transformed from a rural to an industrial base.
Lignite coal beds in this area were deposited during the Middle
to Late Eocene time as units of the Domengine Formation in this
region. These coal beds were deposited when the climate was warm,
humid and favorable for the growth of swampy vegetation. Lignite,
often referred to as brown coal, is a soft brown fuel with
characteristics that put it somewhere between coal and peat. It is
considered the lowest rank of coal, and was used almost exclusively
as a fuel for steam-electric power generation. Lignite is
brownish-black in color and has a carbon content of around 25-35%,
a high inherent moisture content sometimes as high as 66%, and an
ash content ranging from 6% to 19%.
Begin your journey at the historical plaque at the posted
coordinates. Head down the road to the slag heap (N37 57.389 W121
51.860), then continue down the road and up the hill to the Eureka
Slope (N37 57.280 W121 51.937).
In order to log a find on this cache you must send me an email
with the answers to the following questions and post a picture of
your party with your log:
1. Estimate the height and volume of the slag
2. How many tons of coal were hoisted out of the Eureka
Slope.
3. Enjoy yourself exploring this great park.
Don't forget to include a picture of your party at the entrance
to the slope with the "find" log.
For more information on the park and tours, visit the East Bay
Parks Website at:
East Bay Parks