Eureka weekly sentinel. [volume] (Eureka, Nev.) 1887-1902, 1897-10-30
TINE foRMA TIsHs WHICH ARE 0RE-BfAR.
ING AND THOSE WHICH SEPARATE
THEM.
Adduced From the Records Of the
u. n. Geological survey OF the
Research OF the Author.

OF the AutnOrs
Written for the Sentinel" by N. II. Joseph
Mineral Hill, which occupies the north
ern slope of Prospect Mountain, is com
posed OF dolomitic limestone and granite.
= The Prospect Mountain qusrtzite, which
there dipping to she northeast, forms the
footwall OF the Ruby Hill lode. overlies
the granite and bends around Prospect
Mountain to the east and west in the form
of q horseshoe, trending on the east side
to a point northeast OF and near the Eu-
reks Tunnel and on the west side to an
other point extended westward from the
Grant mine. There il sinks beneath the
surface debris, but again appears above
the mountain quarternary just southwest
of and near the Prospect Mountain Tun-
mel, and still further south il underlies the
Prospect Mountain limestone east OF and
near the Dug Out mine. On the east flank
Of Prospect Mountain the qusrtzite dips
to the east. The granite, which owes its
exposure on the n%ortherly slope Of Pros
pect Mountain to erosion, apparently dips
under the quartzite Of Ruby Hill. Pre-
vious to the erosion, the great belt of lime
stone Of Prospect Mountain aud that
which constitutes the Ruby Hill lode were
presumably one and the same and formed
q continuous body. The face Of the
quartzite dips under the limestone OF the
Ruby Hill lode at an average angle OF
about 40 degrees to the northeast. The
exposure Of this body Of limestone on the
surface extends over A. 900 linear feet from
near the Albion shaft on the northwest.
where il 10 covered BY the debris Of Spring
Valley 70 . point southeast Of and beyond
the Jackson mine, where 10 comes to q mar
row point or wedge between the Prospect
Mountain quartzite and Pogonip lime
stone. On the northern end OF Ruby Hill
the limestone 10 cut off by a fault ~issure,
called the "Ruby Hill fault" The width
OF the limestone zone Of Ruby Hill. at the
surface, Ia from 800 to 1000 feet; over
lying 10 on the north are the Secret Can
yon shale and the Hamburg limestone Of
Adams Hill. Overlying the quArtzite.
upon the east side OF Prospect Mountain,
is q belt Of Hamburg limestone. which IL
doubtless connected 81 some depth beneath
the surface with that OF Adams Hill. In
tervening those two bodies al the surface,
over 9 space Of about 5000 feet, is the
Pogouip limestone, which rum In q CON.
tinuous belt through the eastern portion
Of the district. from Diamond Valley,
north OF the Bullwhscker mine to Newark
Valley on the south. O~verlying the Ham
burg limestone OF Prospect Mountain is q
band Of srgilsoeous shsle Identical in char
acter with that which overlies the north.
ern part Of the Ruby Hill lode, but known
IS the Hamburg shale. Nearly all Of
H ORE BODIES
OF considerable magnitude and economic
value that we're discovered in Eureka Dis
trict up 10 the present time were in the
Prospect Mountain and Hamburg lime
stone formations, Of the Csmbrisn Age,
but valuable deposits OF ore have been
found in the Bullwhscker and Williams-
burg mines. which are in the Pogonip
limestone and quartz ~porphyry OF the ST.
lurian Age. Very rich ore has been found
in paying deposits 10 the mines OF New
York Canyon, In Lone Mountain lime
stone. also Of the Silurian Age. The Lone
Mountain limestone Is separated from the
Pogonip limestone by the hard quartzite
reef of McCoy's Ridge. This quartzite
extends northward TO Oariboo Hill and
southwark to Newark Valley.
The shales and qusrtzites are subsssn-
TALLY non-ore- bearing. In some places
the Prospect Mountain quartzite In Ruby
Hill has been impregnated with the ore
bearing solutions, but II has nowhere been
found OF any economic value. Rhyolite,
q species Of the porphyry class OF rocks.
igneous and non-ore bearing, is found in
dykes OF various dimensions in several
parts Of the district and frequently in di-
rect touob with the ore bearing strata.
The solfatsric action consequent upon its
eruption had probably much to do with
the ascending ore bearing solutions. il not
with the actual deposition OF the ore.
Trending %southerly from the end Of the
quartzite, on the east side OF Prospect
Mountain, Is q belt Of Secret Canyon shale,
which separates the Hamburg limestone
from the Prospect Mountain limestone
throughout the southern section OF the
district. The Prospects Mountain and
limestonss are identical In char
acter in all but that the latter is more
than the former. and il weathers
rougher and breaks with q sharper frac-
ture. Returning to the
RUBY HILL FAULT.
II is first observed n~orthward. at the sur
face near the Albion mine, taking an al
most uniform southessserly course, with
an average dip. underground. OF about 10
TO the northeast. It passes near
The Richmond Office and is plainly visible
near the mouth OF a tunnel THAI was for
merly run to connect with the Bell shaft;
thence northeast of the Eureka and
Z K shafts to q point between the Phenix
md Jackson mines, where 10 bends around