Contrary
to the usual law of metals, where gold is concerned, it is, the upper
and not the lower portions of veins which are prolific. This arises
from the violent action of water on the surface,—and hence, in general,
arises the argument that there must be mountains to produce much gold
in valleys. It is generally found, moreover, that moderately high
mountains produce the most gold. The most prolific gold-fields of
Russia are at the base of hills not more than 1,500 feet high whilst
those at the base of hills rising to 5,000 feet and and upwards, are
not nearly so prolific in gold. Hence it is probable that the most
fruitful discoveries in Australia have yet to come, and the gold-fields
of of Port Phillip are a direct proof of the argument as the hills
where gold has chiefly been found are of moderate elevation.
A brief notice of the distribution of gold generally will be of use to the intending emigrant.
The
diluvial deposits are found in the beds of streams and in the valleys
around, the latter having been at one time covered with the waters of
the stream. Gold is also deposited in a limited height above these
valleys—frequently to the summit of the higher lands in the
neighbourhood, these having been at some remote period under water
also, when the gold was deposited as in the streams. The metal, under
these circumstances is found in sand, gravel, on clay beneath the
gravel, and amongst the debris of rocks, and is continuous as to its
quality a'nd frequently as regards the given contents per cubic fathom.
Diggings where the deposits are of this nature are the most productive,
and reward the most unskilful miner; no machinery beyond a cradle, or
some equally simple contrivance, is requisite. The materials for
carrying on the pursuit are easily procured—the returns quick—and the
whole establishment is readily removed as the gold becomes exhausted.
Much
of the gold found in these diluvial deposits is wasted from the rude
manner in which it is sought for; the miner being unable to detect it
except in lumps or scales which are palpable to his eye. In Australia,
numbers of reputed exhausted diggings will be well worth going over
again with more skilful appliances, and the labour will be
comparatively easy, from the previous loosening and removal of the
earth from its bed.
The
gold has not been generated in the streams, valleys and high lands,
over which it is scattered;—but has been washed down from the primary
or non-fossiliferous rocks, the most common of these gold-bearing rocks
being quartz, granite, or perphyry, and sometimes slate, the gold soil
of the lower lands being merely the detritus of the primary formations.
The
intelligent miner will hence look for the seat or matrix from which the
gold has been carried—not by itself, but imbedded in rocks which have
subsequently been abraded and washed away by the violence of the
floods, the gold itself, from its weight, remaining nearly on the same
spot in which is finally parted from its rocky envelope. The veins and
beds in which it is orginally found, generally exist in mountains of
secondary height, and these are the more likely to contain gold, the
more they are parallel to the meridian. Under these circumstances it is
found imbedded in the rocks, often in a state imperceptible to the eye,
the nuggets which are found being no doubt the result of fusion of the
primary rocks when the latter were in a state of ignition. Rock mining
can only be carried on successfully by machinery of various kinds, as
pumps, stamps, &c.; and this machinery, being of a costly nature,
must be permanent, so that great judgment has to be exercised as to the
productive qualities and extent of the gold bearing rocks, as a large
outlay must be made before any profit can arise. Even at the best, gold
veins are of a temporary nature, as a few years' continuous labour
exhausts the product, and it is now well known, that in the majority of
veins, at very moderate depths, the gold gradually and regularly
diminishes in quantity, though in some cases it improves slightly in
quality, yet at last the* expense of producing the metal is greater
than the yield. The history of old gold mines does, not prove the veins to be entirely exhausted, but only that tfcj
