Gold is never met with in regular veins, but in primitive or igneous rocks, or in deposits formed by the disintegration of these. In Australia the metal is associated with quartz, in slate rocks geologically equivalent to the Cambrian formations of England and Wales; and in California it is also chiefly found in material which has been formed by the wearing down of quartz and granite rocks. Before the discoveries in California and Australia most of the gold in circulation was obtained from auriferous iron pyrites. The first finding of gold in California occurred in September, 1847, when a Mr. Marshall, the proprietor of a saw-mill on the Sacramento River, observed some glistening grains among the sand in his mill-race. The news soon spread, and the inhabitants of the town of San Francisco, then numbering about two hundred persons, were greatly excited thereby. When it became known that gold was really to be found, multitudes flocked to California, the population of San Francisco rapidly increased, and at the present day the city contains nearly a thousand times as many inhabitants as it did at the time gold was first discovered. The annual value of the metal found in California averaged about £23,000,000 for ten years after 1851; but this subsequently declined to less than half in 1872.
Sir Roderick Murchison, the distinguished geologist, pointed out the great probability of the existence of gold in Australia many years before the precious metal was actually found. It has, however, been stated that gold was met with in Australia so long ago as 1788. Considering the mode in which the metal occurs, it seems strange that the emigrants who occupied the auriferous districts as agriculturists did not long ago discover the riches which Nature had scattered over the surface of the soil. No doubt, their attention was too much devoted to their sheep and cattle to notice the glittering particles which might be seen in the water-courses, and it would probably never enter their minds that the eagerly desired metal could lie exposed to view on the surface of the land. But the announcement of the discoveries in California induced men to look at the soil more attentively, and in April, 1851, Mr. Hargreaves appears to have found at Bathurst the first gold met with in Australia. Four months afterwards the metal was also picked up at Ballarat, Victoria, and the gold-fields so discovered proved even richer than those of Sydney.
The effect of this discovery on the colony of Victoria proved marvellous. The population, which in 1851 was 77,000, had in 1867 become 660,000; in the same period the land under cultivation expanded from 57,000 acres to 631,000, and the value of property rose enormously when the grazier’s estimate of its worth was replaced by that of the miner. The authorities of the colony from the first regulated the mining operations by enactments defining the rights of the miners to the “claims,” as the allotments of land for working upon are termed; and thus disorder and lawlessness were almost unknown. Fig. [329] will give the reader a notion of the appearance of a miners’ settlement in the Australian gold-fields in the earlier period.
Fig. 329.—Gold Miners’ Camp.
The fundamental rocks in the colony of Victoria belong to the oldest series of strata. They answer to the Silurian formation which exists in Cumberland, Wales, and Scotland. Although the strata of the rocks are much bent, and they have been worn down by the action of water, they are as a whole but little altered, consisting chiefly of sandstones and shales. These strata are interpenetrated by innumerable veins of quartz, which vary in thickness from 1
16 in. to 150 ft. It is in these quartz veins that the gold is seen in its original matrix. The metal is sometimes in the form of grains or flakes, or in moss-like threads, embedded in the quartz; sometimes in the form of well-defined crystals, sometimes in rough lumps or nuggets. Fig. [330] shows three of the various modes in which the gold is found disseminated through quartz. Overlying the more ancient rocks with their auriferous quartz veins are various rocks of different ages; and as these have been in part formed by the wearing down of the older rocks, they also are in general auriferous, and contain the gold in detached pieces, varying in size from particles of fine dust to the huge nugget, containing 2,280 oz., or nearly £10,000 worth of pure gold, which was found at Dunolly.
The soil, which has been formed by the disintegration of masses of auriferous quartz, is full of gold, so that a patch of such soil 12 ft. square has been known to yield 30 oz. of gold by a very rough kind of washing to the depth of 1 ft. Soil of this kind has been carried down by rivers and streams ages ago; and the lighter particles having been carried off by the water, while the gold, from its greater specific gravity, remained at the bottom of the stream, the sands and gravel of these river-beds are very rich in gold. In many instances the ancient water-courses have been entirely covered by igneous rocks, such as basalt, which have flowed over the land in a molten state. The gold-miner often finds his reward in burrowing beneath these basalts and lavas, following the bed of the ancient river, and recovering its long-buried treasures.
Fig. 330.—Gold in Rocks.
