Statewide County CA Archives History - Books .....Quartz Mining And Milling 1891
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Book Title: Memorial And Biographical History Of Northern California

QUARTZ MINING AND MILLING.

  The following, from Hittell's Resources of California, is a concise
description of quartz mining and methods:

  No doubt, geological knowledge is valuable to a miner, and it should assist
him in prospecting; but it (that which the professional geologist has above the
practical miner) has never yet enabled anybody to find a valuable claim.
[Similar observations are made with regard to oil and gas discoveries in the
East.] Chemists, geologists, mineralogists and old miners have not done better
than ignorant men and new-comers. Most of the best veins have been discovered by
poor and ignorant men.

  Auriferous quartz lodes are often found by accident. Some good leads have been
found by men employed in making roads and cutting ditches. The quartz might be
coveted with soil, but the pick and shovel revealed its position and wealth. In
Tuolumne County, in 1858, a hunter shot a grizzly bear on the side of a steep
canon, and this animal tumbling down was caught by a projecting point of rock.
The hunter followed his game, and-while skinning the animal discovered that the
point of rock was auriferous quartz. In Mariposa County, in 1855, a miner was
attacked by a robber, and the former saw a sparkle behind his assailant at a
spot where a bullet struck a wall of rock. He killed the robber and found that
the rock was gold-bearing quartz! In Nevada County, a number of years ago, a
couple of unfortunate miners who had prepared to leave California and were out
on a drunken frolic, started a large bowlder down a steep hill. On its way down
it struck a brown rock and broke a portion of it off, exposing a vein of white
quartz which proved to be auriferous. This induced the miners to remain some
months longer in the State, and paid them well for remaining.

  After all, the author proceeds to compile a few scientific rules for
gold-hunting, as follows:

  It is useless to prospect for auriferous quartz in a country where no placer
gold has been found. If the metal exists in the rock, some of it will also be
found in the alluvium, and it can be discovered there more readily than in the
vein. After the placers have been found, search should be made for the quartz.
The following rules are serviceable:

  1. If a ravine is rich in gold to a certain point and barren above, look for a
quartz vein in the hill-sides just above the place where the richness ceases.

  2. A line of pieces of quartz rock observed in a hillside probably indicates
the course of a quartz vein.

  3. If a ravine crosses a quartz vein, fragments of the rock will be found in
its bed below.

  4. A large quartz vein will often show its presence in the topography of the
country by forming hills in those spots where the rock happens to be very hard.

  5. Quartz can be found and the veins traced with comparatively little labor in
the steep banks of canons where the rock is bare or is covered with but little
soil.

  6. If a quartz vein contains gold, some of the metal may be perceptible to the
naked eye.

  The extraction of auriferous quartz does not differ materially from that of
other ores in narrow veins. The rules for running tunnels and drifts for
sloping, draining, ventilating and timbering are precisely the same. Extraction,
however, requires much experience and judgment for proper management. The dip,
the thickness and material of the vein, the horizontal length and the dip of the
pay chute, the character of the walls, the supply of water and the situation of
the mill must be taken into consideration. Access must be had to the lower works
by a horizontal tunnel or vertical shaft, or an incline running down on the dip
of the lode. There are, however, very few auriferous quartz mines in which the
lower works can be reached profitably by a tunnel. Ordinarily an incline is
preferred, which goes down in the vein-stone, and sometimes, but rarely, pays
for the work of taking it out. After the shaft or incline is down, levels or
drifts are run off horizontally as far as the pay rock extends, at intervals
usually of a hundred feet, and the levels are numbered from the surface; so when
we read that they have found good rock in a certain mine at the eighth level, we
presume that it is about BOO feet below the surface. The rock between two levels
is broken down or sloped out, and it falls to the drift or level below, where it
is loaded in a car and hauled to the shaft, in which it is carried up.

  Nearly all the quartz of California is crushed by stamps or iron hammers ten
inches in diameter and weighing 500 pounds. The stamp is fastened to a vertical
iron stem about six feet long, and near the top is a projection by which a cam
or revolving shaft lifts the stamp a foot high and then lets it fall. Five
stamps are placed side by side in a battery, and they fall successively, each
making about forty blows in a minute. The quartz is shoveled in on the upper
side, and when pulverized sufficiently it is carried away through a wire screen
on the lower side of a stream of water, which pours into the battery steadily.

  The arrastra is the simplest instrument for grinding auriferous quartz. It is
a circular bed of stone from eight to twenty feet in diameter, on which the
quartz is ground by a large stone dragged round and round by horse or mule
power. There are two kinds of arrastras, the rude and the improved. The rude
arrastra is made with a pavement of unhewn flat stones, which are usually laid
down in clay. The pavement of the improved arrastra is made of hewn stone cut
very accurately and laid down in cement. In the center of the bed is an upright
post which turns on a pivot; and running through the post is a horizontal bar,
projecting on each side, to the outer edge of the pavement. On each arm of this
bar is attached by a chain a large flat stone or muller, weighing from 300 to
500 pounds. It is so hung that the forward end is about an inch above the bed,
and the hind end drags on the bed and crushes the quartz

  The pulverized auriferous quartz, as it comes from the stamps, consists office
particles of rock and gold mixed together, and the aim of the miner is to
separate them, save the metal and let the other material escape. Here again a
small sluice, similar in principle to that used in mining, is employed; but
instead of riffle bars the bottom of the sluice is copper covered with
quicksilver, or is a rough blanket, in which the gold and heaviest sands are
caught. In many mills quicksilver is placed in the battery, two ounces of
quicksilver for one of gold; and about two-thirds of the gold is thus caught.
Next to the battery is the apron, a copper plate covered with quicksilver, on
which a good share of the gold is caught.

  Below the aprons, different devices for catching the gold are used in
different mills. The blanket is the most common. This is a coarse article, laid
at the bottom of the sluice, through which the pulp from the battery runs, and
the gold, black sand and sulphurets are caught in the wool, while the lighter
material runs off. The blanket is washed out in a tub at intervals of half an
hour to an hour.

  In some mines nearly half the gold is mixed with pyrites and refuses to be
caught with quicksilver. In such a case a sluice may be used to separate the
sulphurets, which may form three per cent, of the pulverized rock. This
separation is called concentration, and the material obtained is concentrated
tailings. The sulphurets are five times as heavy as "water and twice as heavy as
quartz; so the separating is not difficult when the supply of water is abundant.

  In roasting for chlorination we have, first, to oxydize the iron and next, by
the introduction of salt, to chloridize certain other substances winch vary with
the locality from which the ore is obtained. When this is rightly done, we have
usually formed either oxydes or oxychlorids of all the base metals in the ore
treated, leaving gold as the only free metal to absorb the chlorine gas. In
order to be successful in roasting the ore, attention must he given to the
construction of the furnace. If the arch over the hearth is too high, the ore
will not be oxydized; so also if the flues are too large or the damper is opened
too wide, as the excess of cold air or draft cools the ore. The cost of the
entire process does not exceed $20 per ton.

  Many fine fortunes have been lost in gold-quartz mining; and it is proper to
give warning to the ignorant against the dangers that beset the business.

  1. Gold-quartz mining is one of the most uncertain of all occupations.

  2. No amount of experience, scientific knowledge and prudence will secure the
investor against loss.

  3. Many of the men engaged in it are very bold, and their statements must not
be accepted without great caution, even when there is proof of their sincerity.

  4. No one should risk more in gold quartz than be can afford to lose without
serious inconvenience.

  5. The presence of large lumps of gold in a vein is no evidence of a
profitable mine. Most of the best mines have had little rich rock; and the
finest specimens have come from mines that are not now worked. It is the large
supply of paying quartz, and not the extraordinary richness of small pieces,
that makes the great mine.

  6. There is no occupation in which it is easier to waste money by
inexperience, carelessness or folly.

  7. No business has greater need of the presence and constant attention of an
economical, attentive and capable manager, directly interested in the business.

  8. For persons of small means, the only safe way to work a small mine is to
make it pay as it goes along, and to abandon it when the outgo exceeds the income.

  9. Many of the best quartz mines in the State were rich at the surface, and
have yielded more than enough from the beginning to pay for all the work
expended upon them.

  10. Not one in five of the mines which did not pay at the surface, and has
been worked to a depth of 100 feet, has ever paid.


  11. The richness of a vein at one point is no evidence of its richness at
another.

  12. Not one quartz miner in a thousand has made a moderate fortune.

  13. Nearly all the owners of the rich quartz mines of California are
capitalists, who made money in other business, and then could afford to risk
considerable sums in ventures which they considered uncertain.

  14. Do not build your mill until you have opened your mine and got enough pay
rock in sight to pay for it.

  An old mining engineer says: "In 1858 there were upward of 280 quartz mills in
California, each one of which was supplied with quartz from one or more veins.
The number of stamps in these mills was 3,010, and the total cost of the whole
mill property of this nature in the State exceeded $3,000,000. In the summer of
1861, only three years afterward, there wore only some forty or fifty mills in
successful operation, several of which were at that time leading a very
precarious existence."


Additional Comments:
Extracted from

Memorial and Biographical History of Northern California.

Illustrated, Containing a History of this Important Section of the Pacific Coast
from the Earliest Period of its Occupancy to the Present Time, together with
Glimpses of its Prospective Future; Full-Page Steel Portraits of its most
Eminent Men, and Biographical Mention of many of its Pioneers and also of
Prominent Citizens of To-day.

"A people that takes no pride in the noble achievements of remote ancestors will
never achieve anything worthy to be remembered with pride by remote
descendents." – Macauley.

CHICAGO
THE LEWIS PUBLISHING COMPANY
1891.


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