Eureka weekly sentinel. [volume] (Eureka, Nev.) 1887-1902, 1897-09-18
the FORMATIONS WHICH ARE oeE-BfAR-
ING AND THOSE WHICH SEPARATE
THEM.
Adduced From m Records OF the
u. y. Geological survey Of the
Fortteth Parallel and the Personal
Research OF the Author.

Written for the "SentineI" by NJ. II. Joseph.l
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 the 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 a horseshoe, trending on the east side
to a point northeast of and near the Eu-
reka 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 Tuu-
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 quartzite dips
to the east. The granite, which owes its
exposure on the northerly slope of Pros.
poet Mountain to erosion, apparently dips
under the qusrtzite of Ruby Hill. Pre-
vious to the erosion, the great belt OF lime
stone Of Prospect Mountain and 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 4 1000 linear feet from
near the Albion shaft on the northwest,
where il 10 covered by the debris OF Spring
Valley TO q point southeast OF and beyond
the Jackson mine, where ID comes to a mar
row point or wedge between the Prospect
Mountain quartzite and Pogonip lime
stone. On the northern end Of Ruby Hill
the limestone is cut off by q fault fissure,
called the 'Ruby Hill fault" The width
of the limestone zone of Ruby Hill. at the
surface. Is from 300 to 2.000 feet; over
lying II on the north are the Secret Gam
yon shale and the Hamburg limestone of
Adams Hill. Overlying the quArtzite.
upon the east side Of Prospect Mountain,
Ia q belt Of Hamburg limestone. which is
doubtless connected at some depth beneath
the surface with that of Adams Hill. In
tervening those two bodies at the surface,
over q space OF about 5000 feet, Is the
Pogonip limestone, which runs in a con-
tinuous belt through the eastern portion
Of the district. from Diamond Valley,
north OF the Buliwhacker mine to Newark
Valley on the south. Overlying the Ham,
burg limestone of Prospects Mountain is q
band OF argilaceous shale 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
THE ORE BODIES
OF considerable magnitude and economic
value that were discovered in Eureka Dis
trict up TO the present time were In the
Prospect Mountain and Hamburg lime
stone formations. Of the Cambrisn 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 In 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 qusrtzite
extends northward to Cariboo Hill and
southwark to Newark Valley.
The shales and quartzites are substan-
TALLY non-ore-bearing. In some places
the Prospect Mountain quartzite in Ruby
Hill has been impregnAted with the ore
bearing solutions, but IL has nowhere been
found Of any economic value. Rhyolite,
q species of the porphyry class OF rocks,
igneous and ore-be bearing, is found in
dykes OF various dimensions in several
parts Of the district and frequently in di-
rect touch with the ore bearing strata.
The solfstaric 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 g 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
Hamburg limestones are identical in char
acter in all but that the latter is more
s~ilicious than the former. and ii weathers
rougher and breaks with q sharper frac- |
ture. Returning to the
RUBY HILL FAULT.
II Ia fret observed northward, at the sur
face near the Albion mine, taking an al |
most uniform southeasterly course, with !
average dip. underground, OF about 20
degrees to the northeast. 1t passes near
the Richmond Office and is plainly visible
near the mouth Of q tunnel that was for
merly run to connect with the Bell shaft;
thence northeast. Of the Eureka and
Z K shafts 10 Q point between the Phenix
md Jackson mines, where II bends around