Rogue River courier. (Grants Pass, Or.) 1886-1927, 1911-05-26
INDICATIONS
OF ORE SHOOTS
Tc the Editor Of the Mining and Sci
entific Press:

Sir--ln his discussion OF my orig
inal contribution under the above
title. In the Mining and Scientific
Press Of October %, 1910. T. A.
Richard, In the Issue Of April 5.
calls attention to a new phase OF the
subject, namely, the depth Of ore
occurrences as related to the present
surface. How far Mr.. Richards the
0ry will apply, am sure ! do not
know have thought that in s
mountainous country, where veins
traverse the hills and gulches, out
cropping on the highest ridges,
down their sides, and often appear
Ing in the bottoms of the gulches
OF canyons, that It was not unrea-
sonable to expect the veins or fis-
sures observed on the hilltops to ex-
tend downward into the earth at
least as deep as the outcrops found
In the neighboring canyons. This
has been my idea, or hope, though (
am not prepared to offer much sub
stantial proof OF the correctness of
my theory. On the mother lode OF
California the veins are found out
cropping on the hilltops, often form
Ing conspicuous objects In the land
esape, as exempllfled at Pinlon
Blanco, In Mariposa county; at
Quartz mountain, In Tuolumne coun-
ty; Carson hill, In Calaveras coun-
ty; and Seaton hill, In Amador coun-
ty In this great lode the fissures
extend not only as deep as the levels
OF the bottoms of the nelghboring
guiches, but thousands of feet be-
low them. The apex of some of the
ore shoots In these fissures does not
come within 1000 feet OF the sur,
lace. However. the mother lode may
DC assumed to be an exception to
the rule, though the present relief
OF the country traversed by Il is
Insignificant as compared to the
depth already reached by some OF
the mines along Its course. The
probable depth OF erosion has been
estimated at 5000 feet.
IL have in mind another region
OF California, In San Diego county.
known as the Julian district, In
which minerallzed zone extends
across the country In a direction
somewhat north of west for several
niles With a few most Important
mines of the district are situated be-
tween the villages of Julian and
Banner, four miles distant from each
other. Julian is at an altitude or
1900 feet and Banner is at $500
feet, difference of 400 feet In al.
titude. The rocks of the region are
mica-slate, mica -schlst, and granite.
Dikes OF pegmatite are common In
the mineral zone. There are four dis
tlnct lines of naturalization. For
the most part the veins" occur as
q succession OF quartz lenses I'm the
schlst and slate. SO far as | am
aware there are no fssure veins I'm
the district. In the Cincinnati pelle
mine, near Banner. Is found flssure
fllled with fragments OF country
rock and clay, but as far ss known
II contains no profitable quartz,
II lies a few feet distant from and
parallel TO the aurlferous quartz
lenses, In which Is found the real
value OF the vein. These lenses OF
quartz have resulted from the filtra-
uon OF silica into zone OF crumpled
and folded slate and schlst, deform-
ed by compressive stress which had
tendency TO cause reverse fault
(as Indicated by local torsion OF the
rccks) but which stopped short of
producing an abrupt fracture. II
seems hardly possible that this
stress, the unmistakable evidence OF
which may be seen along the sur
face and underground for several
miles, In these hills, should have
been exorted only near the present
surface, or even confined 10 zone
extending from region 900 or 400
feet below the present surface no
to pre-oxisting surface approxl.
mately conforming TO contcpr TO the
present outcrop, a few hurcred feet
higher. II such be the caso, then
these veins come within tho llmita-
uons OF vein formation suggested by
Mr. Rlckard II the stress extended
TO a deeper-seated region, then there
would be n reasonable probability OF
the veins of the district also extend.
ing to FAR greater depth than has |
over been reached IN any OF tho {
mines. Several local a lthoritles
have varlouely estimated the OUTPUT !
't this district az from $4,000. 600 I
% SO,O00,00O The smaller amount :
8 probably nearer the truth. The I,
're was undoubtedly OF good average !,
irade, and some OF Il wonderfully e
lch, Without doubt much OF the a