The herald., 1893-12-10
SOME RULES FOR FINDING GOLD
Methods by Which TO Locate
Gold Ledses.
An Old Pacific Coaster Writes on
The Science of Mining.
Ehs .t-nttet %. Contact veins-vsricties
or Aseuro Voina-Chimneys
and shoots aud
LOdes.
iDan do suille in Ban Francisco chronicle.l

tDan do suille in 6an Francisco Chronicle.l
In every quartz mining region there
are iistufs systems which are more or
!eas regular, much depending upon the
kirds OF ro * in which they are formed.
The miner or prospectcr soon finds that
very important relations exist between
dikes snd other bodies of igneous rock
and ore deposits. Whatever the nature
OF the stratiied rocks, sections OF the
country where no bodies of eruotive
rocks arc found ara but poor in miner
als. This is on account OF the dikes
opening passage during the process OF
their uphsaval from those deep-seated
regions whence rise mineral charged
vapors and emanations from metals in
fiery depths; therefore the part they
play in lode formation is more mechani-
cal than chemical. They merely open
passage upward from natures secret
laboratory, in unknown and unknowable
eubterranean depths.
The fiseuree in which the mineralizsd
veins are formed are what might bo
termed mechanical accidents, as they
owe their existence 10 the yielding of
the superintendent country rock at the
point OF least resistance at the time Of
the upheaval. The assures thus formed
the process of filing commences, some
doubtless affording q better and more
free passage than others to the ascend
ing mineral charged vapors.
The veins spoken of by miners as be-
ing contact veins" are usually such az
are in contact with some intruded rock
on the surface, being situated at the
junction OF stratified rocks with those of
igneous origin. either in the shape of
mountain masses or as narrow dikes.
Other veins are at the surface in slate or
other stratified rock, with no igneous
rocks visible in the immediate vicinity.
The lodes found so situated would not be
spoken of by miner as contact VEINS"
rs they have the same rock for both
walls. At q lower depth below the sed-
imentary rock granite, diorite or some
other igDeous rock will be reached when
the lode will be found to be q contact
vein lying between the intruded igneous
rock and the superincumbent stratified
rock. Thus it will be seen that all lodes
are doubtless contact veins at some point
below the surface, but in most cases at
greater depth than is likely to be at
tanned by the miner. Were the overly
ing sedimentary rock sufficiently tough
and yielding to bear the strain of up
heaval without cracking there would be
no veins thus formed except contact
veins. as all would lie between the up
lifted strstifed rock and the intruded
igneous dixie.
The secondary fssures are the result
of fractures produced in the stratiied
rocks while they are being lifted during
the elevation OF mountain masses OF
granite, or tho upheaval of dikes or
other igneous rocks, and they have both
walls of the same kind OF rock. The
real contact fssure would be found
above at the point where stratified rock
abuts upon the intruded igneous rock.
This contact fssure might be very small,
merely parting between the two kinds
of rock, filled with crushed material
from the walls, while below in the over
lying Btratifed rock would be found
very much larger assures, and in some
of them-that having the best openings
and most favorable situation would be
found the principal lode formation. In
the other parallel assures would be
found other veins, all exhibiting the
characteristics OF the principal lode.
III the gold comes from any Of the
wall rocks it must be at great depth,
where there is intense heat and great
chemical action-at point where all
the metals are much more abundant
than near the surface. The nature of
the mineral solutions and the metallic
vapors filling and passing up through
the assures have more to do with the
character OF the vein formed than have
the wall rocks.
Mineral veins frequently intersect one
another. When the intersecting vein
fills fssure in the intersected it shows
it to be more recent, the younger of the
two. Some veins are intimately COM
bined at the point of junction, showing
them to have been filed at the same
time. As rule the work of filling i'm
mediately follows the formation of the
fissure. A vein intersected by young
or vein is generally rich, as it receives q
double charge of mineralized solutions.
"Chimneys" or "shoots" of ore in
vein are probably owing to a consider
able extent to the character of the
6ssure at a greater depth. Though
open and roomy near the top the fssure
may be narrow or wholly closed at
deeper level, thus permitting the metal
lie vapors to ascend only at certain
points. Thus we see steam rises in col
umns along the open fssures of hot
springs not in continuous sheet. Wide
pihCoe III Velu arc nOT6 lhVOrhDl6 10
ore formation than narrow ones. In
narrow places the motion OF the ascend
ps mineral bearing solution or vapors
pore rapid, therefore not 80 favorable
formation OF deposits as the wider
ifses. This may cause the apparent
p14chiDg out' of a vein. At such
places no sign o. the vein will be seen
except q seam of clay. but if this is fol-
lowed it ia apt to lead to broad place
ia tho vein filed with both quartz and
ore. Ia some veine-owing to the
irregular fracture of the rock forming
the wals-there are found a succession
OF those pinches.
1t is quite certain that mineral vcina
have been filled by circulation in the
hesufe. in which they are found, of
heascd water, aqueous vapors and various
Aeses, ali more or less mineralized. All
veins have not been formed in the same
way, nor by means of vapors and smana-
tiuns of the came character. No two
veins are exactly alike in all respects.
Mad the veins been filled by means of
4 molten matter from below Gas many sup
pose) their metallic contents would have
hcea tho same in all parts, and would
have bsen evenly distributed.
There would have been no ''bonauzas'
or ''chimneys" OF rich ore, with barren
upaces between. There can be nothing
,,, .bo l<.se