Amador ledger., 1902-04-11
KEYSTONE MINE and MILL
Still in the Infancy Of it's
Career.
The Mill and Hosting Plant are
Modern Structures Mine
Developments.

A few years back it was thought that
the days of the Keystone at Amador
City as a bullion producer were num-
bered. 1t was one of the first mines to
bring the quartz industry of Amador
county into prominence, and for more
than 40 years has continued to sur
render generously of the precious
metal. Owing to the discovery that
large masses of quartz, heretofore re-
garded as waste and Improbable, car
ried gold in paying quantities, the mine
has just entered upon new era of
production, which bids fair to outclass
the remarks able history of the past.
MILLING AND HOIST PLANT.
Through the kindness of C. E.
| Bunker, the superintendent, we we're
shown through the recently recon-
structed mill and hoisting plant. The
old 40 stamp mill has been remodeled
and 20 additional stamps added, max
ing 10 stamps in all. The 40 stamps
are $50 pounds each, with crushing
capacity of 81 tons per stamp per day.
The new portion of the mill is provided
with 1000 pound stamps, and it is cal
culated that these will be equal to 5
tons per day, although this has not
been proven as yet as months run
has not been made.
One of the noticeable features about
| the mill is the absence of wood, wher-
ever that material can be dispensed
| with. The mortar blocks are all of
concrete; the floors are of cement, and
the concentrators and other machinery
are bolted into the artificial rock floors.
The spacious building 70 feet wide and
over 100 feet long, is of galvanized iron.
In the new part of the mill the ANAL
gamating plates are 20 feet long, as
against IL feet for the others. A pair
of six foot Frue concentrators is pro-
vided for each battery of five stamps.
The Wood bury concentrators, after a
thorough trial, have been discarded
for the Frue. The last named ma
chine seems to be better adapted for
the gold ores met with on the main
belt of this county. In some sections
of the county, where different class
of ore has to be- treated, preference is
given to the Wiley or Woodbury. pat
ent, but on the mother lode it is well
settled that better results are secured
with the Frue. This fact has been
strikingly exemplitied at the Keystone.
While the WoodburSs were in use,
tailings or slime plant was kept run
ming, the owners making good living
out of it. But as soon as these ma
chimes were displaced for Frues, the
business of catching sulphurets below
the mill proved Improbable. and the
tailings plant has been long since
abandoned. An electric motor of 150
horse power runs the 60 stamp mill.
The hoisting works now operated by
steam, are soon to be run by an air
compressor operated by 300 horse
power dynamo. After leaving the
compressor the air will be superheated
so as to ensure greater efficiency. Heat,
as is well known, expands air, and by
the application of heat in its compressed
form greater motive force is secured.
With steam it equires 6 cords of wood
per day to run the hoist. With the
new works, one cord per day will be
sufficient to increase the temperature
of the compressed air to the proper
standard. AT the time of our visit the
machinery of the air compressor and
motor was all in place and ready to be
started. 1t is estimated to hoist 100
skips of Il tons each per day, and also
$50 skips of water of $50 gallons each.
MINE DEVELOPMENTS.
The Keystone, Notwithstanding it
has more years of constant activity to
its credit than any mine in the county,
is still in the infancy of its career. The
magnificent milling and hoisting equip
ment just described has been provided
with a full knowledge of what the
underground developments warrant.
The lowest working level at present is
800 feet deep. There is a deeper level,
at the 1000 feet, but this is full of
water, the necessity for unwatering it
has not yet arrived. The truth is the
possibilities of mining on the mother
lode are only just beginning to be ap-
preciated. With the Keystone it is
not a question of deep mining. The
ore bodies lying comparatively near to
the surface promise to supply food for
the mill for another generation at least.
1t has been found that the gold-bear-
ing material consists of at least four
veins. Those lying close to and in con-
tact with the slate have been the pro-
ductive ones in the past. But at the
distance of about 800 feet east of the
slate an immense body of grey schist is
met with. This, although of quartz
nature, has not been recognized as
milling ore, doubtless for the reason
that it was considered too poor in the
precious metal to prove profitable. Its
presence has been known for a long
time, but it certainly would not have
met the demands of the expensive
methods of early days, and hence was
not exploited to any extent. 1t is this
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