Eureka daily sentinel. [volume] (Eureka, Nev.) 1871-1887, 1874-05-13

uonbted igneous origin, that We aro
iorccd 10 tile conclusion that thew wero
components of the original deposit
such is particularly the case I'm thc
Lake Superior region. and i'm Robinson
district, Nevada. Specimen of a,nyp-
daioia trap from the former mines
contain threads of metallic copper rum
nihg through the substance of the rock
IN all directions, and also grains of the
same metal in great abundance. Under
certain circumstances this metal might
be the product of the decomposition of
some OF the ores of copper; but had
such decomposition taken place here.
would not the containing rock show
some evidence Of it? Or, in the case
OF those large masses Of metallic COP
per. would it he possible that they
could be prccipilated in a metal
lie state from thin solutions. and
that, too, in The presence of re-
agents such as the fixed alkalies. that
would most probably precipitate a por-
ton OF the solution, at least, as a car
Donate? The presence of crystals of
calclte or Of metallic copper in crystals
oi quartz does not at all initiate
against the theory of contemporaneous
| injection or OF SublimatiOn, either of
| which Will serve to account for the
phenomenon. Quartz and calcite are
almost always cOmponcnts of amvy,la-
loid traps; and il is easily possible for
them to crystalline i'm cavities contain
ing particles of metallic copper. That
such is the ease, is proved by the fac,
that the copper is in nearly all cases at
the base of the crystal. 1t would he
| quite as RI reasonable to contend hat the
trap was not an igneOus product be.
cause it contained those crystals as to
contend that the copper was not con-
temporhncous deposit, because of their
presence.
In the central portion Of the Robin
son mineral belt, Of Nevada, rhvolite
occurs abundantly, large areas of
which are completely ilnpregnated
with copper minerals, not in the seams
only, but completely through the sub
stance OF the rock. Near the surface
and where exposed to dccompoSing
AGENCIES, inalacliite is the prevailing
mineral; but this is replaced with cha
copyritc at a depth of twenty feet from
The surface. Assays for silver show
traces of that metal up to 80 80 per ton.
The largest area containing copper i'm
preE,,ations is about 16O acres. besides
Which there are several small ones
varying i'll size from ten to thirty acres.
No lOueS occur in the immediate vicin-
liy. though therearc some we'll defined
f>SnreS about half a mile distant. The
urincin,l GRO in tho loIe ;s hl,c,. .rd
red oxide win cnnsilnr,I,e ,no.aiI;,
conner. and malachite.
1t is also pretty certain that ro,d i>
sometimes found in igneolls rocks un-
der circumstances. that would pl lecludc
tle po,sibilny of its getting there
rhro,irh auuenus aoen,.ieS case nt
the Kind Ocuui. in Tie bunker fiilt
mining district, Lander county, Neva-
da. y dixie OF igneouS granite, about
twelve feet thick, inclosed II argilla-
rou> slate. contains traces OF gold up
to 80 per ton.
The almost universal occurrence OF
lodcs can scarcely he deemed an s.ccl-
dental circumstance. According to
Won Gotta, and other reliable authori-
te|, they are found closely associated
in nearly all the principal mining dis
trict> of Europe. And s. far as inves-
tigatcd, the same rule applies with
equal force on this continent; the re-
verse is the exception. From the Lake
Superior copper region to the gold ana
quicksilver belts OF California, there Is
scarcely district but contains iEncouS
rocks in proximity to metallic lodeS.
Indeed, so common is the occurrence
that there is no need of naming amy
special case. In South America the
same rule holds good. Only those To-
cailic> are prolific i'll minerals in
| which igneouS rocks abound. as III
the northern district of Atacania. i'll
Chilli; and lluanataya and Cerro Pas
co. in Peru.
The region of country comprising
the Rocky Mountains, the Great Basin.
and the Sierra Nevada range to the
Pacific Ocean on the one hand, and
from Bchring Straits to the l>thmu> OF
Panama, and thence through South
America to Magellan straits ON the
Wher' """ c"'ie>!"""1 S"'.
~. nnl ;n,.lud;nr tho nd iarent
;.;a,Js Of J,n,n tho Indian Au.hi-
re,a~o. and Australia. and New
Io,,5ni have hern in the mast. as
,i.,," ,na,, ,r, in the ~re"ont more charac-
,ms ,"r;.,;cal,v % " volc,nic tl,an anv like area
"n ,',l.; ,hn Surface Of the e,r,h: they are
also M NOR" nrolitic of huge iodcs of
az" 49, '"""I 1 fn',;'.l silror ..onnar and
S,,.b', S..,, ,a,,,s S ,,,,m anw othcr Known re-.