CALIFORNIA.
Section I.—Geological Features.
In
confining myself in this paper to the really metal-producing districts
visited in the State of California, I may, however, in passing state
that that country is traversed nearly north and south by the Sierra
Nevada Mountains, which obtain an altitude of over 8,000 feet above
sea-level. The western slopes comprise California, whilst to the east
the State of Nevada is located. The base of the Californian side is
formed of Tertiary drifts or gravels, which partly constitute further
inland the " Foot-Hills," or one of the terraces rising above the
fertile lands along the Sacramento and other rivers. Above these
foot-hills, the country becomes rapidly more and more mountainous, and
thus the gold-bearing regions occur at an elevation varying from 2,000
to 4,000 feet above the Bay of San Francisco, forming an almost
uninterrupted metalliferous belt, not only within California proper,
but likewise in portions of Arizona in the south, and Oregon
territories in the north, extending many hundreds of miles in those
directions.
Having
explored, as far as my time would permit, the following counties in the
State—viz., Nevada, Sierra, Calaveras, Tuolumne, and Mariposa—it will
be seen that these areas cover a large extent of country, which,
however, do not include all the other mining regions equally worthy of
notice, but which I was prevented from visiting during the three months
only at my disposal in America. In all the counties visited, however,
nearly the same geological features were observed, with but few
unimportant departures from the general character and position of the
country rocks and the quartziferous gold-bearing lodes those rocks
enclosed. And, as the well-established quartz mining district near
Grass Valley City, Nevada County, attracted my first attention on
account of its leading position amongst the others, a concise
description of the place will, I submit, suffice for all present
practical purposes, and at the same time elucidate the condition,
geologically considered, of other and similar mines as well (Plate No.
I.).
The
Kate Hayes mine, south-west of the City of Grass Valley, is situated
upon an eminence, which permits of an extensive view up to the
snow-clad Sierra Nevada in the far distance, and, in the more immediate
neighborhood, of all the mines worked or in the course of exploitation
; besides, the first-mentioned mine occupies a position on that central
belt of coarse feldspathic granite bearing N. 20° E., which divides the
sedimentary and metamorphic rocks as well as the serpentines and
syenites, which latter occur here as the enclosing or " wall rocks " of
nearly all the quartz lodes, with this difference, that the strike of
the first-named is nearly due east by west with frequent alterations,
thus differing materially from our regular Silurian strata at Bendigo
and elsewhere. The arrows in black shown on the chart at the lodes
named and delineated, denote both their dip and underlay, which, it
will be seen, not only varies considerably, but demonstrates besides a
total want of regularity and continuity in the line of strike such as
we are accustomed to in Victoria, and which circumstance, in
California, is doubtless
B
