Page 171 - calmining1890

CONTRA COSTA COUNTY. 165

CONTRA COSTA COUNTY.

By W. A. Goodyear, Geologist and Assistant in the Field.

At the old Mount Diablo mines at Somersville, on the first of May,
1890, a small amount of coal was being extracted from the old Eureka
Company's ground; but none of the other mines at Somersville were
producing any coal. The Pittsburg Company, however, after having
failed in an attempt to pump out, clean, and retimber the old Independ-
ent shaft, were then employed in sinking a new shaft at a point about
one hundred feet north of their old hoisting works, at the mouth of the
slope. This shaft had then reached a depth of two hundred and thirty
feet. It is in two compartments, timbered with eight by eight-inch
timber, each compartment measuring seven feet eight inches by four
feet eight inches inside the timbers.
The Stewart Mine, also, was idle at this time, while the old Empire
Mine, after going down one thousand two hundred feet on the dip of the
bed and producing a very large quantity of coal, has long since been
abandoned.
A short distance to the west of the old Empire Mine, however, a new
slope has been sunk, which is called the West Hartley, and through
this slope they are now working on both the Clark and Little veins.
The slope is said to be four hundred and fifty feet deep, and the coal at
the bottom three feet thick.
It is probable that the Stewart Mine will be again opened, and con-
tinue to produce a large quantity of coal for a considerable length of
time to come.
Some four or five miles southerly from Martinez a locality was visited
on the property of the Smith Brothers, where some prospecting has been
done for coal, and a tunnel has been driven some twenty-five or thirty
feet into the hill. But the rocks are highly metamorphic, and no indi-
cations exist to justify any hopes of finding coal here. Some very strong
mineral waters, however, were found, which vary considerably in char-
acter. Some of the water is supersaturated as it issues from the rocks
with sulphuretted hydrogen gas, which escapes from it in bubbles; while
some of it is a very strong solution of various alkaline salts, among which
the sulphates seem to predominate. Some three quarters of a mile north-
westerly from here, in the bottom of a very steep caiion, there is a beauti-
ful, strong, and copious sulphur spring, whose water seems to contain
but little else than sulphuretted hydrogen. All these waters are cold.
The locality of basalt rock on the lands of Matthewson & Blackmar,
about three and one half miles from Concord, which is referred to on
page 162 of the Eighth Annual Report, was again visited. It appears to
be a completely isolated outburst, roughly oblong in form, and with its
longer axis lying in a direction of north 45 degrees to 50 degrees west
magnetic. Its extreme length is little, if any, more than a mile, while
its greatest visible width may, perhaps, be a little over a quarter of a
mile. Its occurrence here is especially noteworthy as being the only
instance where volcanic rocks, or indeed eruptive rocks of any kind, are
yet known to exist in places anywhere in Contra Costa County, while
none whatever are known in Alameda County.
12 27