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14
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MINING IN CALIFORNIA AND NEVADA.
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the
surface, and, right here, the continuity of lodes to a great depth has
been proved in a very convincing sort of a way. As this is a very
mountainous region, the valleys are frequently from 1,000 to 2,000 feet
deep, and from the summits of the mountains down to their base these
reefs are exposed to view, maintaining the same width and extent of
each "pay-chimney" or " chute," or the blocks in which they may be
enclosed, with the aggregation of richer, poorer, or worthless quartz,
the same as in Victoria. Comparing the yields, as taken from many
official records, a similar fluctuation is observed as with us, and, as
this may be of some interest, I append a short statement obtained from
the books of the frequently mentioned Idaho mine, Grass Valley City,
showing the yield of various levels, viz.:—
At and above the 300-foot level, which was worked by the Eureka Company, the average. yield was returned at 100 dollars, i.e., about
5 oz. of gold per ton. The 400 and 500-foot levels were poor for the
whole extent worked, whilst the 600, 700, and 800-foot levels produced
quartz that fluctuated from 25 to .35 dollars per ton. The 900-foot
level averaged about 35 dollars; and the 1,000-foot, according to late
advices, state that a higher average is being obtained from this
company's deepest level. The Alaska mine, in the same locality, had
also very rich ore in the deep ground; the Pittsburg and New
Providence, Nevada County; the Rising, Sun, Colfax; the Golden Gate,
Sonora City, Tuolumne County; the Banderitos, Skendlin, Marble Vein,
Haslon, Derrick, and others, near Coulterville, Mariposa County, all
exhibited this same satisfactory feature in their bottom levels.
On
the whole, I may state that, in most of the Californian mines I have
inspected, the quartz looked and yielded as well, and in many cases
better, in the deep ground than it had done nearer the surface. I took
particular care and trouble to assure myself of this fact, by reference
to the official reports and accounts kept by the mine superintendents
and secretaries, and I submit that this information should be of value
to us in our deeper mining operations.
AURIFEROUS SLATES.
These
remarkable formations have given rise to extensive operations near
Coulterville and other places. The Ferguson Company, near the former
city, was successfully engaged on a vein or stratum nearly vertical in
position; and this talcose, friable slate was impregnated with thin,
flat, and very fine flakes of gold for a varying thickness of the vein
of from 12 inches to 6 feet. Owing to the frangible nature of this
slate, and on account of the light character of the gold in it, which,
after crushing, formed a " pulp" of very little specific gravity, the
utmost care had to be exercised both in the concentration and
amalgamation of these atomic grains of gold. I would not have referred
to this remarkable occurrence, or have described lower down the process
adopted for treatment^ were it not that frequently our Bendigo lodes
diminished first in size, and then passed gradually into a soft,
deep-black slate (flucan), also impregnated with very fine gold, which
we cannot very successfully collect with our appliances ; so that, by
adopting the Californian method, we might add to our yields of gold
from similar formations.
DILUVIAL GOLD-BEAKING GRAVELS AND DEEP LEADS.
These
important deposits are very appropriately termed "ancient rivers" in
California, and the extent of their extensive watersheds must have
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