The White Pine news. [volume] (Treasure City, Nev.) 1868-1906, 1906-08-17
THE GEOLOGY OF
ROBINSON DISTRICT
Continued from Page l

sor says that, unfortunately the car
Donates of copper disseminated as they
are rather dilfusely through the por
phyry do not lend themselves to or
binary processes of concentration as
does the chalcocite. In order to handle
this ore, therefore, it may be necessary
to resort to some teaching process.
The prophyry thus charged with cop
per carbonate has otherwise the char
acter of the zone of oxidation at the
Ruth, except, perhaps, that kaoliniza-
ton has not proceeded so far and that
the rock is fairly strong and coherent.
Between this zone of oxidation with its
content of copper carbonate and the
ground water, there is as in the case of
the Ruth certain depth of the sulphide
zone in dry condition down into which
the oxidized rock extends irregularly.
This sulphide zone both above and be-
low the level of the ground water re-
sembles closely that at the Ruth. 1t is
blush white porphpry impregnated
with pyrite and chalcocite. Locally it
has in it nests of bronzy or brownish
mica in foils of considerable size. The
mica appears to be secondary and is
said by the miners to occur in those
portions of the porphyry where the
content of chalcocite is highest.
RICH ORE IN UPPER ZONE
The upper part of the unoxidized
zone at Copper Flat carries higher cop
per values than the deeper ground, and
doubtless represents zone of enrich
ment by downward teaching at a for
mer higher stage of the waterplane.
The general average value of the ore
in the unoxidized ground differs but lit
tie from that at the Ruth.
1t is probable that the copper ore of
the oXidized zone existed earlier as
chalcocite, itself product of secondary
concentration. and that in the oxidation
! process an excess of carbonic acid de-
termined the standardization of the cop
per ore disseminated through the rock.
The presence of this carbonic acid
may perhaps be ascribed to later per-
iod of eruptivity which gave rise to
flows of rhyolite. remnants of which
are to be found in the vicinity of Cop
per Flat.
With the exception of the mines at
the Ruth and Copper Flat practically
all other attempts at copper mining in
the district have been made upon rather
unsatisfactory and limited deposits of
chalcopyrite either on the contact zones
of the intrusive rocks or in the quartz
blout.
Toward the conclusion of his bulletin,
Professor Lawson thus summarizes:
1t appears that in the vicinity of the
Ruth, without considering the mines
farther east, there are three we'll
marked zones of metalliferous deposits,
viz:
/. A central one containing sulphides
of iron and copper in the porphyry.
2. A southern one carrying gold in
the limestones below the porphyry.
3. A northern one carrying argen-
tiferous galena with subordinate zinc
and copper minerals in the lime over
the porphyry.
The segregation of the metals in this
photographic or structural relation to
the porphyry is a most interesting fact,
but with the limited data available it
would perhaps be unwise to attach too
much significance to it. The fact is
here recorded in the hope that it may
prove useful when considered in con-
nection with similar observations else
where in sufficient abundance to lead to