GEOLOGY. 63 
the Copper Cafion ore has been exported. There are rich 
veins of copper-ore near Crescent City, in Del Norte county; 
but, with the present high prices of labor and coal, they cannot 
be profitably wrought. Vitreous copper is found at William- 
son’s Pass, sixty miles from Los Angeles. 
§ 44. Coal.—The old red sandstone and the “true carbon-* 
iferous” rocks, as they are called, are wanting in California; 
and it was long supposed that no valuable coal would ever be 
discovered in the state; but within the last year some veins 
of avery good quality have been found near Mount Diablo. 
The mineral belongs to the tertiary epoch, but contains far 
more solid combustible matter and less incombustible material 
than most tertiary coal. In the strict geological meaning of 
the terms, it is not “coal,” but “lignite,” belonging to a later 
date than the true coal, and lying in a different formation. 
The rocks are sandstone and shale, of the upper tertiary or 
pliocene age, and were formed by alternating depositions in 
salt and fresh water. The coal-veins are situated on the north- 
eastern slope of Mount Diablo, are from two to nine feet in 
thickness, dip to the north at an average of 30°, and open on 
the southern declivities of the hills. A chemical analysis of 
some of the best specimens showed 50 per cent. of carbon, 46 
per cent. of volatile bituminous substances, and 4 per cent. of 
ashes. The coal is bituminous in character, breaks readily, 
shows a bright surface where fractured, and burns with a 
brilliant flame. The quantity is large, and it can be profitably 
supplied in San Francisco at eight dollars per ton, whereas 
imported coal has hitherto cost twice as much. 
§ 45. Asphaltum.—Bituminous springs are numerous near 
the coast, from thg northern line of Monterey county to San 
Diego. They throw up a dark, pitch-like fluid, of a strong 
odor, which on exposure to the-air grows thick, and finally 
solid. It collects in great masses about the springs, and in 
some places covers several acres of ground. After being ex- 
posed to the air for some time, it is called “ asphaltum,” which 
is very hard in cold weather, but grows soft at about 75°, and 
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