Eureka weekly sentinel. [volume] (Eureka, Nev.) 1887-1902, 1897-12-11
the FORMATIONS WHICH ARE 0RE-BfAR.
ING AND THOSE WHICH SEPARATE
THEM.
Addueea From the Records Of the
u. n. Geological survey OF the
Fortteth Parallel aud the Personal
Research Of the Author.

tWraea for he Sentinel BY N. II. Joseph
Mineral Hill, which occupies the north
ern slope Of Prospec. Mountain. is com
posed OF dolom!tic limestone and granite.
y The Prospect Mountain quartzite. 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 a horseshoe, trending on the east slde
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 qu~arternary 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 Ont mine. On the east flank
OF Prospect Mountain the qnsrtzise dips
to the east. The granite, which owes its
exposure on the northerly 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 and that
which constitutes the Ruby Hill lode we're
presumably one and the same and formed
y COutl1uOus UUuls 41o iaCo VI ~
qusrtziss 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 1000 linear feet from
near the Albion shaft on the northwest.
where il 10 covered BY the debris OF Spring
Valley 10 q point southeast OF and bsyond
the Jackson mine, where 10 to a mar.
row point or wedge between the Prospect
Mountain qusrtzite and Pogonip lime
stone. On the northern end OF Ruby Hill
tho limestone IL cut of by a fault fssure,
called the RUBY Hill fault" The width
OF the limestone zone OF Ruby Hill. at the
surface, 10 from 800 to 1000 feet; ovsr-
lying IL on the north are the Secret Can
yon shals and the Hamburg limestone Of
Adams Hill. 0verlyins the quartsits.
upon the east side OF Prospect Mountain.
IL 9 belt Of Hamburg iimsstons. which Ia
doubtless connected 81 some depth beneath
tina surface with that OF Adams Hill. To-
tervening thoss two bodies NJ the ~anrfacs.
over q space OF abous 5000 feet, is the
Pogonip limestone, which rum in q pom
tinuous belt through the eastern portion
Of the district. from Diamond Valley,
north OF the Bullwhscksr mine 10 Newark
Valley on the south. 0vesiying the Ham
burg limestone OF Prospect Mountain 10 q
band OF argilaceoua shals identical In char.
acter with that which ~overliss the north
srn part OF the Ruby Hill lode. bat known
90 the Hamburg shsls. Nearly all OF
THE ORE BODIES
or considerable magnitude and economic
value that we're discovered In Eureka Dis
trics up TO the present time we're 10 the
Prospect Mountain and Hamburg lime
stone formations, Of the Cambriau Age,
but valuable deposits OF ore have been
found in the Builwhscker and Williams
burg mines. which are in the Pogonip
limestone aud 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 lie separated from the
Pogonip Limestone by the hard quartzite
reef of MoCoy's Ridge. This qusrtzise
extends ~northwsrd to Oariboo Hill and
southwark to Newark Valley.
The shales and quartzites are substsn-
TALLY non ore bearing. In soms places
the Prospect Mountain quartzite in Ruby
Hill has been im~pregnated with the ore
bearing solutions. but 1t has Nowhere been
found Of any economic value. Rhyolite,
q species Of the porphyry class OF rocks,
lSlcOus huQ DCoAiuSs 10 lOuuQ III
dykes OF various dimensions in several
parts of the district and frequently in di-
rect touch with the ore bearing strata.
The solfataric action consequent upon its
eruption had probably much to do with
the ascending ore bearing solutions, il moi
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 Prospect Mountain and
Hamburg limestones 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 frst observed northward. at the sur
face near the Albion mine, taking an al
most uniform southessterly course, with
an average dip. underground, OF about 20
TO the northeast. 1t passes near
The Richmond Office and is plainly visible
hear the mouth Of q tunnel that was for
nerly run to connect with the Bell shaft;
hence northeast Of the Eureka and
( z shafts 70 . point between the Phenix
nd Jsoksen mines, whore 70 bends around