The border vidette., 1931-06-27
MINING PRACTICE AT vAlEOON
NEW MEXICO

Mining methods at the Eighty.
Five mines of the Calumet and
Arizona Mining Co.. near Vale
don, New Mexico, are discussed
ia an Information circular just
issued by the United States
Bureau of Mines, Department of
Commerce. written by Ralph B.
YOutz.
A production of 1000 to 5000
tons per month Of siliceous cop
per- gold-silver ore is mined from
steep veins occurring in igneous
country rocks. chiefly granodio
rite. Ore shoots are persistent,
and veins, ranging from 2 to 10
feet wide, average feet in
width, usually with commercial
rather than structural limits. 10
the upper levels both walls and
vein filing are hard and firm,
and will stand open indefinitely,
but below the 1850 level more
intense naturalization of the
walls has taken place, requiring
cot-and-till methods in some
places.
Experience has shown the ore
10 De so uniformly continuous
that the only exploratory work
now practiced consists in the
routine opening up of deeper
levels. With some extra cross.
cutting aud raising near the
ends of the vein. Reserves are
estimated in 100 foot blocks on
the basis of channel samples,
with proper allowance for horses
of waste, dilution, and discrep
ancies between mine and smelter
assays.
The nine is developed in the
usual way by vertical shafts
1.-TWO for operating. use). drifts,
crosscuts. and raises. Develop
ment, drilling and blasting, and
shaft sinking details are we'll
treated. An interesting feature
of the latter is the use of key
board blocking, which has proven
superior to stuli blocking in
shaft timbering. =
Shrinkage has always been
the most important STOPPING me
thod at this property. Inclined
and-till slopes are resorted
to where the walls are very
weak, where the vein is wide but
contains horses or bands Of
waste, or where high-grade ore
occurs in narrow veins. All ore
is hand sorted from a surface
picking belt.
Shrinking STOPPING is usually
done in connection with drift
back timbering, although in wide
veins or where the ore immedi
ately above the drift is of mar
ginal grade, pillars may be lett.
These pillars are usually recov
cradle on completion of the stope
from below, if their grade war
rants. In firm ground cribbed
manways are carried through
the broken ore between slopes.
This necessitates special draw.
ing procedure to prevent crush
ing of the manways by runs of
ore occasioned by unequal draw
ing on the two sides. Ia heavier
or fauited ground, small pillars
are left to protect the manways.
with dog-holes broken through
to the stope at about 3o foot in
tervals. Where foot-wall drifts
have been driven Slopes are car
ried direct to the level above;
other wise the floor pillar may be
recovered later. Ore remaining
ia slopes as drift back pillars or
cones between chutes is pulled
through the stope below. Pres
ent extraction is close to 100 per
cent, although considerable waste
from the walls must 0e SOrteo
out.
Cut and fill stoping is treated
in detail. Pumping is an ion
portant item, some $50 gallons
per minute being raised in sew
eral lifts. Ventilation has be
come a problem in the bottom
level, where the mine water has
a temperature of 104 F. All un
derground labor is on a contract
basis.
Total mining cost in August,
1880, was 81 49 per wet ton with
production of las wet tons
per man shift. In two typical
shrinkage and cut-aud- fill slopes
stopping costs we're 81 % and
81 IS, and 50 IS and $2.37 per