Los Angeles herald., 1910-09-25


usually worked by the drifting process,
| following up on the grade of the
stream and breasting the channel bot
| tom. Gravel exceeding a value of $1.50
per car is generally profitable under
this method of working. Above the
blue graVel' the upper deposit ranges
| to a height as great as $50 to 400 feet,
and throughout this mass of gravel Is
a more or less irregular deposition of
| finer gold and small nuggets. This
upper bank contains an average of
to 10 cents a cubic yard of material,
and to work such gravel at profit re-
quires the handling of immense guam
titles of material at the lowest possible
cost Of recovery Of the gold 1t was
against these banks that the giant
streams Of the hydraulic miner played.
and as the thousands of inches of
water doomed over the sluice block
| and rifles the gravel and clay were
thoroughly disintegrated and the
heavy gold caught in the artificial
| crevices.
MAIN CHANNEL SYSTEMS
Within Nevada county three main
channel systems lead down from the
upper slopes of the western mountain
face, and at North Bloomfield and
Columbia hill the three channels with
their several feeding tributaries unite
in one deep gravel bed of about one
mile in width. The You Bet-Blue
Tent channel from the south with al
most continuous gravel deposits for
twenty miles from Remington hill at
the east the Omega Relief hill gravel
beds, with intermittent deposits on the
hill slope south of the South Yuba
river and the Orleans Moores fiat
gravel banks on the steep slope to the
nj IL CAI ~ h n OF
channel of unbroken tracing has been
worked in part for a distance of six
miles to Badger hill, and again from
San Juan, at four miles westerly, con-
tinuous channel is traced for seven
miles through French corral. At the
westerly boundary of the county at
Mooney fiat the lowest remaining sec
ton of the channel has been mined.
GRASS VALLEY CHANNELS
other than this main. system of
channels, which received its quartz
gravel and gold contents from the veins
of the higher Sierra slope and from
the hillsides along the course of the
stream, there are two smaller systems
of channels in the Nevada City and
the Grass valley districts, separated
from the above described main system
by the long and high SUBMITS of Ban
ner mountain and Osborne hill ana the
connecting ridge.
Immediately north of Nevada City,
on Cement hill, Sugar Loaf and Har-
mony ridge, and to the east near Ban
ner mountain are strong channels
which have been filled with gravel and
gold from the Nevada City, Willow
valley and Banner mountain quartz
veins Gravel from the Harmony
drift mines in this system yielded from
$40 to $1S per ton, and from length
of 5000 feet of channel $4,500,00O was
produced.
AT Grass Valley from the Osborne
hill divide near Kress' summit a chan
mel leads northwesterly through How
ard HILL and at the north side of the
town its continuation enters Alta hill
and meets with the channel from Town
Talk and from the confluence the
deposits of gravel are traceable to
Rough and Ready, four miles west
erly. In the Alta hill workings, about
e-eighth mile of channel yielded
100000.
These low drainage valleys and the
gravel channels were sealed and cap
ned by the outpouring of volcanic rhy-
olite and andesite from the high pla-
teau region east of the Sierras and
the later water drainage has cut new
CANYONS and river beds through the
volcanic cap and the bedrocks ana
these dead river deposits are today
found benched and covered in many
places with hard Gaping, high up on
the hilltop or mountain divide above
and between the present rivers and
streams
PRODUCTION OF GRAVEL MINES
It Is next to impossible to obtain
exact data regarding the total produc-
tion of the hydraulic mines. Estimates
have been published giving the yield
per mile from the upper gravels at
50, 900 to $3,00O,000; the yield per
linear foot of the drift gravels at $lOO
to $500. The total productions from
the hydraulic and drift mines within
Nevada county has probably been
about SAC, ,000, 900 to $50, 900, 900. The rec
ords Of individual mines of the hy-
draulic field show the washing Of from
1000, 900 to as high as 47,0OO,OOO cubic
yards of material with yields of from
: cents to 13 cents from the top gravels
and as high as 85 and 40 cents per yard
from the banks at North San Juan ana
The Columbia Hill mines have
worked about 33,000,000 cubic yards of
gravel, yielding Az to cents average.
and have an estimated reserve of 165,-
100000 yards.
The North Bloomfield mine has pro-
duced over $5,000,00O from gravel yield
ing to 10 cents per yard and it is
estimated there remains $S5,000,0O0 yet
to be extracted.
AT Blue Tent near Nevada City over
IL 900 900 Yards have been worked,
Welding an average of 21a to cents
in the upper gravel and as high as Is
cents per yard in the lower.
At Omega from 600 cubic yards
an average of 1877 cents was produced,
while at You Bet 100000 yards is
credited with $3,5OO,OOO in gold.
Probably the most prominent drift
mine developed in Nevada county was