Eureka weekly sentinel. [volume] (Eureka, Nev.) 1887-1902, 1897-08-21
Eureka District.
DEEPLEVEL MINING
The Ruby Hill Fault Fissure.
ITS EXTENSION SOUTHWARK AND IN
FlUsNcE UPON THE 0HE-BEARlac
STRUCTURE OF RUBY HILL AND
PROSPECT MOUNTAIN.
Ore Still Going Down Below the Lowest
Workings of the Eureka Con. Nine
improvement in Quantity and Quality
Of the Ore in the Diamond and Excel
sior Mines as Depth is Attained--
The Proportion Of Gold Increasing.
the FORMATIONS WHICH ARE 0aE-BfAa-
ING AND THOSE WHICH SEPARATE
THEM.
Adduced From the Records OF the
u. y. Geological survey OF Ii
fortfeth Parallel and the Personai
Research Of the Auth0r.

Forsieth Parallel and The Personal
Research of the Author.
Written for ne "Sentinei" BY N. II. Josephl
Mineral Hill, which occupies the north
ern slope of Prospect Mountain. is com
posed OF dolomitic limestone and granite.
y The Prospect Mountain quartzite, 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 vest in the form
Of a horseshoe, trending On the east side
to q 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 it sinks beneath the
surface debris, but again appears above
the mountain quarterDary just southwest
OF and near the Prospect Mountain Tun-
mel, and still further south it underlies the
Prospect Mountain limestone east OF and
near the Dug Ont 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
pee: Mountain to erosion, apparently dips
under the qusrtzite OF Ruby Hill. Pre-
vious to the erosion, the great belt Of lime
ctO1C Va hO9RG1N 6A4
which constitutes the Ruby Hill lode were
presumably one aud the same and formed
q continuous body. The face Of the
qusrtzite 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 oh the
surface extends over 4, 900 linear feet from
near the Albion shaft on the northwest,
where ii 10 covered by the debris OF Spring
Valley to q point southeast OF and beyond
the Jackson mine, where it comes to a mar
row point or wedge between the Prospect
Mountain qnartzite and Pogonip lime
stone. On the northern end OF Ruby Hill
the limestone is cut off by a fault assure,
called the ''Ruby Hill fault" The width
Of the limestone zone Of Ruby Hill. at the
surface, Is from 800 to 1000 feet; over
lying 1t on the north are the Secret Cam
yon shale and the Hamburg limestone OF
Adams Hill. Overlying the quartzite,
upon the east side Of Prospect Mountain,
10 o belt Of Hamburg limestone. which ia
doubtless connected 81 some depth beneath
the surface with that OF Adams Hill. In
tervening those two bodies 81 the surface,
over q space Of about 5000 feet, is the
Pogonip limestone, which RUM in q oon-
tinuous belt through the eastern portion
Of the district. from Diamond Valley,
north OF the Bullwhscker mine to Newark
Valley on the south. Overlying the Ham
burg limestone Of Prospect Mountain ia q
band OF srgilaceous shale identical In char
acter with that which ~overlies the north
ern part OF the Ruby Hill lode. but known
as the Hamburg shale. Nearly all Of
THE ORE BODIES
OF considerable magnitude and economic
value that were discovered In Eureka Dis
trict up 10 the present time were in the
Prospect Mountain and Hamburg lime
stone formations, of the Csmbrian Age,
but valuable deposits OF ore nave been
found in the ~Bullwhacker 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 Mountsin 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 Cariboo Hill and
southwark to Newark Valley.
The shales and quantities. 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 1t 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 touch 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
quar.zits, on the east side Of Prospect
10 a belt Of Secret Canyon shale,
separates the Ham burg limestone
rom the Prospect Mountain limestone
the southern section Of the
The Prospects Mountain and
Hamburg limestones are identical in char
acter in all but that the latter is more
,ilicious than the former. and it weathers
and breaks with a sharper frae-
lure. Returning TO the
RUBY Hill
q is frat observed northward. at the sur |
ace near the Albion mine, taking an al
most uniform southessterly course, with
u average dip. underground, OF about 10
to the northeast. 1t passes near
be Richmond Office and is plainly visible
ear the mouth of q tunnel that was for
,erly run TO connect with the Bell shaft;
northeast Of the Eureka and
x shafts to Q poin. between the Phenix
Id Jackson mines, where 10 bends around !