Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 5, Pt. 2

SUTTER S MILL-CLAY SLATES-TALCOSE SLATES.
one mile before reaching Smith's house on the river. Trappean intrusions adjoin the granite
abruptly, and quartz is abundant along the junction.
Coloma.-The hills along the South Fork of the American River, at Coloma, are not precipitous, but are rounded, and the valley has considerable width, so that many wide bars, or side
flats, are formed. These consist of river-drift, sand, and gravel, and it is all auriferous.
Much gold is obtained from the projecting points or headlands about which the river turns in
its winding course. These points are formed of granite, and the gold is washed out of the
overlying drift by the miners, as at Nevada and elsewhere. The ground-sluices are made use
of here also.
This is the point at which the gold was first discovered in the race of Sutter's saw-mill. This
mill is still standing, although going rapidly to decay and ruin. It is said that it has recently
been purchased with the intention of manufacturing walking-canes from its timbers.
It is claimed that the piece of gold first found is still in this place, and in the possession of
Peter Weimar. It is a very pretty, flattened lump, about an inch long, and five-eighths broad.
The claim that this is thefirst fragment found is, however, disputed.
The river is crossed at this place by a long wooden bridge. The current is rapid and very
muddy. An immense quantity of fine earth must be constantly transported by this and the
many other rivers of the mining region to the delta of the Sacramento and San Joaquin, and
even further down into the bay. All the streams from the mining region are made thick with
the tailings of the thousand sluices that drain into them.
COLOMA TO GEORGETOWN.
At Irish Creek, about three miles from Sonora, the slate is again seen in distinct outcrops,
trending from N. 32~ to N. 40~ W., with an easterly dip of 70~ or 80~. It is a compact, finegrained clay slate, like roofing slate, and is traversed by many thin and parallel intrusions of
trappean rock. These are dykes, with a width of from six to ten and twenty feet. The canon
or ravine of the creek is narrow, and conforms in its direction to the trend of the slates. The
outcrops of the dykes are chiefly confined to the bed of the creek. These dykes, together with
the slates, are traversed by seams and veins of quartz containing pyrites, and many large cubes
of this mineral are found in the slates. No well defined vein of auriferous pyrites was observed,
but one has been worked in the vicinity, as shown by heaps of refuse and a shed, under which
one of Blaisdell's " coffee-mill" crushers was placed. The beautiful octahedral and dendritic
crystals which I purchased in San Francisco were obtained at some point along this creek.
At Kelsey's, several miles beyond, the slates are not so much like roofing slates, but are
more talcose or magnesian, and include veins or beds of auriferous quartz, trending parallel
with the stratification. A vein which has been prospected near the town is three feet wide,
and consists of intercalations of quartz in lenticular masses, with thin films of the slates. The
vein thus appears to be subdivided by thin layers of the slate.
Between Kelsey's and Georgetown there are many interesting mining localities; among them,
Spanish flats, where the alluvial drift is very rich.
Georgetown.-This beautifully situated mining town is about N:N.E. of Coloma, and2,500
feet above the sea. It is regularly laid out, with wide streets, and already has its church and
theatre. The underlying rocks are argillaceous and talcose slates of a light color, and in very
regular, thin, and flat lamineg.
The mining-operations are chiefly at Mameluke Hill, in or under a deep deposit of drift or
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