be
remarked that these ledges are found in extensive belts of granite,
which run west and east, and as the lodes strike north by a little
south, besides exhibiting other characteristics, it may be safely
inferred that they are true fissure veins, according to
Californian theories, and therefore permanent. This view is strongly
supported by the fact that numerous blocks, or "makes," as described
above, formed against the "main back," were worked by this proprietary,
and that, at their bottom level (800 feet), another block had just been
cut into, resembling all those at the higher levels; this new discovery
proved, after proper tests had been made of the ore, exceptionally rich
in gold-bearing pyrites. There are quite a number of mines here also
located in the granite country, but, as their general character
resembles that which has been said of the New Providence mine, I
consider all present purposes of this paper have been served, and
consequently I proceed to the description of mines differing from any
hitherto referred to.
The
Pittsburg is situated a short distance east of the granitic belt, in
which the New Providence and other mines are located, and about three
miles south of that mine; this lode, however, occurs in a kind of
coarse sandstone, which is farther on metamorphosed into greenstone
syenites, traversed by strong dykes of diorite, highly crystalline and
easily distinguished at the surface. I regret not having been able to
investigate these interesting features more closely, owing to the short
time at my disposal, especially as this formation would ultimately join
a belt of lodes in the south, occurring, however, in chloritic schists
and serpentines; the time at my disposal would be utilized by the more
practical matters, of which the elaborate treatment of the quartz after
crushing would engross all my attention. This Pittsburg lode ranges
from 15 inches to 3 feet in width, and the ore averages from 20 to 50
dollars per ton, inclusive of the 5 per cent, of sulphurets it is
charged with. The latter, after careful concentration and chlorination,
have, however, given as high as 110 dollars per ton (American ton,
2,000 lbs.). In this mine the same rule has been found to prevail as
mentioned in regard to the behaviour of the blocks of ore on a western
or eastern underlay, thus affording a field for geological deductions
as to the dynamic and kindred forces in action previous to, during, and
since the formation of these and similar metalliferous deposits. As
regards the frequently discussed and mooted existence of " barren zones," or
country at one time very prolific in rich ores becoming quite devoid of
such ores, I may state that I have arrived at the conclusion that these
are only temporary occurrences if compared with what I saw in
California. After careful examination, I offer the following
conclusions for consideration, as tending to dispel doubts, and,
instead, to encourage " deep quartz mining" with more confidence of
success and for permanent results than many regard the stability of our
lodes in Victoria :—
1st. I observed no "saddle" or anticlinal reefs or ledges in California.
2nd. That in California isolated lodes were more frequent than they are here in Victoria.
3rd.
That in a few instances a " line of reef," in the Bendigonian
accepÂtation of the term, was found to exist, but that these lodes were
in themselves very irregular, and that the barren country intervening
betwixt the blocks or makes of ore would amount to as much as the
actual quantity of gold-bearing quartz.
4th. That in California the occurrence of payable ledges was subject to more irregularity than, generally speaking, in Victoria.
