White Pine news weekly mining review. [volume] (East Ely, Nev.) 1910-1920, 1912-06-16
DEEP ORE BODIES
IN ELY DISTRICT.
GEOLOGY OF COPPER BEARING
ROCK SHOWS INTERESTING
FORMATION IN THE WEALTH
Producing METALS.
(By Walter Harvey Weed.)

brown and only occasionally shows
stains or PARTICLES of green copper
ores. This oxidized material variea
from SO to $50 feet thick, and 1t is
this coating of cached AMI worthless
overburden which deceiyes prospect
ors. This material, beneath the sur
face exposures, is pale ~yellowisa, and
shows but little if an trace of the
original texture of the porphyry. 1t
is sometimes difficult to distinguish
between it and the oxidized altered
limestone of the contact zone about
the porphyry.
Beneath the oxidized material the
ore is white or blush, considerable of
it being erumbly and soft in texture.
1t consists of a much silicifed and
seriticized porphyry, with many mi
mute quartz yeinlets, carrying films
and seams of fresh pyrite and of
chalcocite. Specks of chalcocite
pepper the body of the ore. There is
also much granular sugary quartz.
The best ore, carrying 3 per cent or
more of copper, is most siliceous.
Gradations occur to lean less silicif-
ed material, and transitions occur
about large nucleal masses of pale
greenish, rotted, but not mineralized
porphyry, a soft material whose al
teration still preserves the teture of
the rock. Such a mass was found in
the steam shovel pit at south end,
lowest level, January, 1910.
The line of separation between ore
and waste is sharp, but is often as ir-
regular as the edge of a saw, yet the
indentations are rarely over 10 to Is
feet deep. Occasional channels of
oxidation run down along fault planes
or zone of crushed rock, but these
are not seen in the big pit. The deptr
of thickness of this Gaping of barren
oxidized material varies greatly. At
the Copper Flat pit it averages 90
feet, but in many sections it is $50
feet.
There is a variats n of copper con-
te.t from a mere race ~ to 3 or 4
per cent. Much o: the Ruth ore
hsty will average G.s per cent. The
PHI 7, duced ore averaging 2.5 per
cent per month. but as now mined It
averages 1.S5 per cent. The ore de-
creases downward in copper content
rather rapidly.
There is from 100 to 200 feet OF
ore before the primary sulphides are
reached, but the downward extent to
which the effect of secondary enrich
ment is noted depends upon the per-
meability of the ore and supply of
copper-bearing water, which varies
considerably. 1t will average $50
feet, but reaches 220 feet in the Gil
roux, and probably averages 200 feet
in the Copper Flat pit. In the Giroux
and Copper Flat properties several
ore, or eve none at all, for 100 to
200 feet beneath the oxidized ma
terial and then encountered good ore
beneath the Iow-grade, non-payable
material. This may be explained by
faulting.
The Ruth ore body, which has been
fairly well defined by underground
work. with an inclined shaft at Al
deg, GAO feet deep, equivalent to 40
feet, vertical, shows so feet of leach
ed porphyry, underlain by an ore body
so to $50 feet wide, 400 to 900 feet
long and $50 feet thick, which Chan
ming estimated at 2,400,0 900 tons.
having an average value of &c per
cent copper. 0.02 OF. gold and 0.05
OF. silver. This ore concentrates 7
tons into one.
The earlier work on the Copper
Flat ore body showed an average
depth of 100 feet of ore, carrying 81
per cent copper, 0.02 OF. gold and
0.03 OF. silver. concentrating 10
into 1.
The ore body shows no distinct
horizontal limits, commercial ole
fading by gradual lessening of copper
content into valueless. slightly min
eraIized material. The clay slips
and friction breccias seen are not
limiting planes, except in so far as
they may make a fault plane cutting
off the ore body, or limit water cir
culation; in other words, we are not
dealing with veins and vein walls,
nor ore deposits bounded by definite
walls. The ore at the Giroux is $50
feet thick, at the Ruth $50, at the pit