Eureka daily sentinel. [volume] (Eureka, Nev.) 1871-1887, 1878-01-26

An Interesting Essay on the Char
acteristics of the Eureka Lode.
We extract the following description
of the Ruby Hill formation from q pa.
per read by w. ). Reyes, Esq, before
the American Institute of Engineers:
The geology of Ruby Hill Is quite
simple. To the south we have q belt
| Of quartzite. Just south Of the claims
Of the Eureka Consolidated and Rich
mond we find the q%usrtzite grooved
out. and forming q narrow gulch rum
ming downl to the valley on the west.
Across this small gulch it rises and
forms . small bare hill. To the east
the quartxite continues along the X X
and Phenix claims, and then turns to
the southeast, behind the claims of the
jackson, Jefferson, Shoe Fly, etc. Su.
perimposed upon the quartzite we find
an altered bed OF doloInitic limestone,
striking easterly and westerly, and
| dipping 4 the north and ~northeasterly.
This forms the meteorological zone,
treated In this paper Is a single lode or
vein, wherein are located the Tiptop
and Richmond claims, the Eureka
Consolidated claims, the X X, Phenix,
Jackson and other claims. Beyond
and geologically above this mineral
lied xone or veined limestone We find
. more or less comfortable belt OF cal
careous and arGilIaceous shales. Still
further to the north and east we find
the horizontally lying beds Of country
limestone, In which are occasional in.
tercslat,ons of an earthy stratum, ap.
parently mari. The strata Of the coun.
try limestone vary Ia thickness from an
inch TO . foot aud over.
THE oUARTzITE.
This forms the foot wall Of the metal.
bearing zone. It's general course
through Ruby Hill is very nearly east
and west and its dip Is variable, being
sometimes nearly vertical, and again
quite fiat; on the average we may call
II about As degrees northerly. It eeins
TO have Sxerted . pred minating in.
fiuence on the deposition and distribu-
ton of the ore bodies In the vein lime.
stone. As early as 1864, Ia Mexico.
aud subsequently in 1857. in Montana
Tel ritory, 1 observed that the more
permanent mines in the dOlomitic
limestones were always found At Or
nes the points OF junction with the
quartxites, thus indicating that the lat
ter had ON bearing on the ore de-
position. This observation has re-
ceived abundant confirmation from the
ore formation and distribution on Ruby
Hill, as will appear more fully In the
following pages.
After leaving Ruby Hill proper, and
just before coming to the Jackson
mine, ws find the quartEite gradually
curving around to the southeast and
south. This change Of direction III the
foot wall gives rise to two anticlinAl
folds in the vein limestone. The main
folding occurs south Of the Phenix,
aud accords with the general north
and south lines of upheaval III the dis
trict. The other. or minor folding. &C.
curs on and near Ruby Hill, where
the vein limestone on the south side
of the bill dips to the south, sud that
on the north side dips TO the north.
As = consequence Of the variation of
strike. We find the quarizite foot wall
bulging or buckiing to the north and
forming great capes. nr ~promontories,
which jut out into the vein-limestone.
Uu the line of claims heretofore men,
toned, we find one very large and two
smaller prOnontories, viz. one 1t the
seventh level OF the X X, where the
foot wall DRIFT makes out far to the
northeast; another at the extreme
westerly end OF the nth level of the
Eureka Consolidated, where the foot
wall surns suddenly to the south; and
another, the largest 1T all, at the ninth
level of the Eureka Consolidated where
its thickness Is shown by the straight
gallery to be 0ver 200 feet. These
capes form wide basins between them,
and In these depressions the ore Is ac-
cumulated. The thickness Of the quartz.
ito loot wall has not yet been dsler-
mined. The X X has driven into it,
at m place, $50 feet; the Eureka drifts
have penetrated II from $50 to 300 feet,
and the Jackson Company has OK
O. explored 1t by drifts for q distance OF
nearly $50 feet. The quartzite on the
plane Of contact with the vein lime.
stone is almost universally stained red
and black with The oxides of iron and
maganess; and where the surface
waters have percolated along il, we
tind It soft, dec0mp0sed, and covered
with . species Of plastic clay, "gouge."
often several feet in thick ness. Where,
on the contrary, the dip Is steep. say
from so TO IS degrees, and unexpOsed
to the action of water. We lind It hard,
aud In close contact with the vein. lime.
stone. Marks of motion are plainly
visible. showing the effects of the slid
ing of the limestone. Often, as In the
Phenix, we observe the ciayey face OF
the foot wall. with = half inch Of man.
gsnese matted upon il, hard. and pol.
ished like ebony, with deep STRIFE run
ming up and down. Near the contact,
and for some distance away from it. we
often find the foot wall irregularly i'm
pregnated with iron pyrites, which, on
assay, yield small amounts of gold.
In but q single instance has this py-
rites been found In q mass OF any mag
nitude, viz, near the Bottom OF the
Phenix shaft. which passed through 1t
for IL feet. Such contact impregna-
tons. as Is we'll known, are quite COM
mon In the wall rocks Of melalliierous
veins.
Near the vein. limestone the quartz