Eureka daily sentinel. [volume] (Eureka, Nev.) 1871-1887, 1878-01-31
THE EUREKA LODE.
characteristics of the Gangue.
Physical Peculiarities OF the Vein
Limestone.

Last week we gave an extract from q
paper prepared by w. S. Keyes, Esq,
and read before the American Institute.
We present below his-remarks on the
vein limestone, or filling of the Eureka
lode:
The most prominent of the physical
appearances OF the vein limestone, is
an entire absence of qualification. with
the single exception of a small space of
the surface ground. near the extreme
western point on Ajax Hill, near the
dividing line between the claims of the
X X and Phenix Companies.
Here the apparently straiified lime.
stone confirms in both strike u dip
t. the underlying qiiartzue. In the
first level of the Phenix, ut y point a
little iart her east, we lind some rem
nanrs Of this strait cation. Tue lime
stone is. however, highly charged with
oxide OF iron, j. soft and muddy. and
%c~uinbles to pieces at u touch Tni>
spot seems ~ have escaped the general
crushing of the strata. On the surface,
aside from the ore ~Outcrops, we hnd
the vein limestone often stained red
aud black with the oxides of iron and
gan also ribbed and streaked
where the carbonate OF lime has been
dissolved out w the pattering rain
drops charged with free carbOnic acid,
leaving the carbonate OF magnesia in
high relief. Below the surface, we Ob.
serve that the vein limestone has been
crushed and shattered in every con-
ceiyable direction, sometimes in huge
blocks, sometimes roughly cru,nbled
like small fray meuts Of marble; again
crushed or d~isintegrated more finely.
like coar.ely powdered glass; aud still
again, as fine rs the fi,est sand. This
sandy Limestone and by the term
sandy. we describe merely its lnechan-
ical aggregation occurs generally over
the ore bodies. and rarely on the foot
wall. When found on the footwall it
is accompanied by large boulders Of
limestone. which appear M II worn
and rounded toy The act ion of water.
This fine material frequently gives
rise to what the miners term ~ run"
filling mp the Slopes. mixing with the
ore, and causing the workings Ia cave
in. Il has not yet been anal, zed, but
is, dnuhtless, the residue OF the less
soluble portion of the dolomite. In
color, it is sometimes nearly white,
sometimes a>hy, drab, BLUSH or red
dish.
The vein limestone is in many places
brecciated and ceinenied together by
calcareous exudatiMns or infilrrations.
This RECOMMENDATION has frequently
been carried 10 such an extent tiiat the
vein matter has lost not only All traces
of IFS original :, ~ratitication, but appears
hard aud compact, and rings under the
hammer. STAINS of iron and manga
ne>e. wigs c~ontaiuining low grade ore,
aud large and small cavities, are found
irregularly distributed throughout.
These cavitit s often form huge nat.
ural many feet in extent, both
lateraliy AMI vertically, the sides and
tops of which are covered with glitter
IN. s~taIactiles and thick incrustalions
of aclcular crystals of arraRonite. In
The bnttOinS OF the caves ore is invari
ally found.
The first discovered of the larger
caverns was near the surface, on the
side OF the hill, beneath the
original ore body of the Champion
clam. THIS was from 80 10 40 feet
wide, about 20 feet high, and some 90
feet long. 1t Law almost in n direct
line above The latest discovered huge
cavern, the largest of all, at the ex-
treine west end of the ninth level of
the Eureka Consolidated. Another
large cavern WAS found about two and
"A half years ago, above the so.called
fifth level of the Eureka, the
roof of which fell in and crushed
through three levels of the mine, kill.
ing several miners. A large cavern was
also found in the second level of the
X X, and in n line herewith "A series Of
such caverns extended downward 10
the fifth level, where one could AL
vance in an easterly direction a dis
lance of $50 feet. Recently, a large
cavern has been discovered in the Jack
son mine, beneath which, AS usual, a
large body OF ore appears.
These caverns form a marked char
acieristic of the vein limestone. They
are nowhere found outside of the min
erallzed M an are due, beyond
question, to the easy solubility OF the
carbonate of lime in surface water
charged with free 0nrbnnic acid,
coupled with the peculiar accessibility
to such waters of the interior OF this
crushed and broken one
This minerallzed one of limestone
varies in width from a few inches up
tn $50 feet, both distances being meas.
ured at n right angle with the under
lying %quartzile. Its mean width is
about go feet. The vein has a greater
apparent width at the surface, near the
center of the Eureka claims. and at
the Richmond. This is due 10 the
crowding over of the limestone to the
south, above a surface fold of the
quarlzite, whence has resulted the
second son,herly dipping anticlinal,
heretofore mentioned. The narrOwest
portion OF the vein is found in the
Jackson claim, where the abrupt
change in course of the footwall has so
far pushed out the quartzite that moth
ing hut n seam of ore is found between
the hanging and footwall.
FOund tn the Mitch.