“The West Mariposa mine, under Colonel Fremont’s lease, has a vein of quartz which runs the whole length of the allotment, averages six feet in thickness, and has been opened in several places. The assay of Messrs Johnson and Mathey states that a poor specimen of 11 oz. 9 dwt. 18 grains, produced of gold 2 dwt. 17 grains, which would give £1347 per ton; and a rich specimen, weighing 17 oz. 12 dwt. gave 3 oz. 15 dwt. 9 grains, being at the rate of £24,482 per ton.”—(Wyld, pp. 36–39.)
The nature and durability of the influence which the discovery and working of these rich veins is likely to have, depends upon their requiring capital, and upon their being in the hands of a limited number of adventurers. In consequence of this they cannot be suddenly exhausted, but may continue to yield a constant supply for an indefinite number of years.
In connection with the durability of this supply from the quartz veins—besides the unsettled question as to the actual number and extent of such veins which further exploration will make out—there is the additional question as to how deep these veins will prove rich in gold. Our readers are probably aware that what are called veins are walls, more or less upright, which rise up from an unknown depth through the beds of rock which we have described as overlying each other like the leaves of a book. This wall generally consists of a different material from that of which the rocks themselves consist, and, where a cliff occurs, penetrated by such veins, can readily be distinguished by its colour from the rocks through which it passes. Now, when these veins contain metallic minerals, it has been long observed that, in descending from the surface, the mineral value of the vein undergoes important alterations. Some are rich immediately under the surface of the ground; others do not become so till a considerable depth is reached; while in others, again, the kind of mineral changes altogether as we descend. In Hungary the richest minerals are met with at a depth of eighty or a hundred fathoms. In Transylvania, veins of gold, in descending, become degraded into veins of lead. In Cornwall, some of the copper veins increase in richness the greater the depth to which the mine is carried; while others, which have yielded copper near the surface, have gradually become rich in tin as the depth increased.[[20]]
Now, in regard to the auriferous quartz veins, it is the result of past experience that they are often rich in the upper part, but become poorer as the explorations are deepened, and soon cease to pay the expense of working. In this respect it is just possible that the Californian veins may not agree with those of the Ural and of other regions, though this is a point which the lapse of years only can settle. Two things, however, are in favour of the greater yield of the Californian veins than those of other countries in past times—that they will be explored by a people who abound in capital, in engineering skill, and in energy, and that it is now ascertained that veins may be profitably rich in gold, though the particles are too small to be discerned by the naked eye. Thus, while all the explorations will be made with skill and economy, many veins will be mined into, which in other countries have been passed over with neglect; and the extraction of gold from all—but especially from the poorer sands and veins—will be aided by the second circumstance to which we have adverted as peculiar to California, the possession of vast stores of quicksilver.
“The most important, if not the most valuable, of the mineral products of this wonderful country, is its quicksilver. The localities of several mines of this metal are already known, but the richest yet discovered is the one called Forbes’s mines, about sixty miles from San Francisco, near San José. Originally discovered and denounced, according to the Mexican laws then in force, it fell under the commercial management of Forbes of Tepic, who also has some interest in it. The original owner of the property on which it is situated, endeavoured to set aside the validity of the denouncement; but whether on tenable grounds or otherwise, I know not. At this mine, by the employment of a small number of labourers, and two common iron kettles for smelting, they have already sold quicksilver to the amount of 200,000 dollars, and have now some two hundred tons of ore awaiting the smelting process. The cinnabar is said to yield from sixty to eighty per cent of pure metal, and there is no doubt that its average product reaches fifty per cent. The effect of these immensely rich deposits of quicksilver, upon the wealth and commerce of the world, can scarcely be too highly estimated, provided they are kept from the clutches of the great monopolists. Not only will its present usefulness in the arts be indefinitely extended and increased by new discoveries of science, but the extensive mines of gold and silver in Mexico, Chili, and Peru, hitherto unproductive, will now be made available by its application.”—(Johnson’s Sights in the Gold Region, p. 201.)
By mere washing with water, it is impossible to extract the finer particles and scales of gold either from the natural sand or from the pounded rock. But an admixture and agitation with quicksilver licks up and dissolves every shining speck, and carries it, with the fluid metal, to the bottom of the vessel. The amalgam, as it is called, of gold and quicksilver thus obtained, when distilled in a close vessel, yields up its quicksilver again with little loss, and leaves the pure gold behind. For the perfect extraction of the gold, therefore, from its ores, quicksilver is absolutely necessary, and it can be performed most cheaply where the latter metal is cheapest and most abundant. Hence the mineral conditions of California seem specially fitted to make it an exception to all gold countries heretofore investigated, or of which we have any detailed accounts. They promise it the ability to supply a large export of gold, probably long after the remunerative freshness of the diggings, properly so called, whether wet or dry, shall have been worn off.
But both the actual yearly produce of gold, and the probable permanence of the supply, have been greatly increased by the still more recent discoveries in Australia. A wider field has been opened up here for speculation and adventure than North-Western America in its best days ever presented. We have already adverted to the circumstances which preceded and attended the discovery of gold in this country, and new research seems daily to add to the number of districts over which the precious metal is spread. It is impossible, however, even to guess over how much of this vast country the gold field may extend, and of richness enough to make washing possible and profitable. The basin of the river Murray, in the feeders of which gold has been found in very many places, has a mean length from north to south of 1400 miles, and a breadth of 400—comprising an area of from 500,000 to 600,000 square miles. This is four times the area of California, and five times that of the British Islands; but whether the gold is generally diffused over this wide area, or whether it is confined to particular and limited localities, there has not as yet been time to ascertain.
It is chiefly in the head waters or feeders of the greater streams which flow through this vast basin that the metal has hitherto been met with; but the peculiar physical character of the creeks, and of the climate in these regions, suggests the probability that the search will be profitably extended downwards along the entire course of the larger rivers. Every reader of Australian tours and travels is aware of the deep and sudden floods to which the great rivers of the country are subject, and of the disastrous inundations to which the banks of the river Murray are liable. The lesser creeks or feeders of this river, in which the washings are now prosecuted, are liable to similar visitations. The Summerhill creek, for example, at its junction with the Lewis river, is described as fifty or sixty yards wide, and the “water as sometimes rising suddenly twenty feet.” Now, supposing the gold drift to have been originally confined to the districts through which the upper waters of these rivers flow, the effect of such floods, repeated year by year, must have been to wash out from their banks and bottoms, and to diffuse along the lower parts of their channels, or of the valleys they flooded, the lighter portions, at least, of metallic riches in which the upper country abounded. The larger particles or lumps may have remained higher up: but all that the force of a deep stream in its sudden flood could carry down, may be expected among the sands and gravels, and in the wider river beds, and occasionally flooded tracts of the lower country. In other words, there is reason to believe that from its head waters on the western slopes of the Australian Alps, to its mouth at Adelaide, the Murray will be found to some degree productive in gold, and more or less remunerative to future diggers.
But there is in reality no reason to believe that the gold of the great Australian basin was ever confined—at least since the region became covered with drift—to the immediate neighbourhood of the mountains, or to the valleys through which its mountain streams pursue their way. We have already fully explained that it is not to the action of existing rivers on the native gold-bearing rocks of the mountain, that the presence of the precious metal in their sands is generally due, but to that of numerous degrading causes, operating simultaneously and at a more ancient period, when the whole valley was covered deep with water. By these, the debris of the mountains here, as in California, must have been spread more or less uniformly over the entire western plain. This vast area, therefore, comprehending so many thousand square miles, may, through all its drifted sands and gravels, be impregnated with metallic particles. Dry diggings, consequently, may be hereafter opened at great distances from the banks of existing streams. Time alone, in fact, can tell over how much of this extensive region it will pay the adventurer to dig and wash the wide-spread depths of drift.
Then there is the province of Victoria, south of the Australian Alps, in which gold is described as most plentiful. The streams which descend from the southern slope of these mountains are numerous, in consequence of the peculiarly large quantity of rain which falls on this part of Australia,[[21]] and over a breadth of 200 miles they are represented as all rich in gold. And besides, the country east of the meridian chain, between Bathurst and the sea, and all the still unknown portion of the Australian continent, have yet to add their stores to those of Victoria and of the basin of the Murray. And though we do not know to what extent quartz veins prevail in the mountains of New South Wales, we have authentic statements as to their existence not very remote from Bathurst, and as to their being rich in gold. Here also, therefore, as in California, there may be a permanent source of gold supply, which may continue to yield, after the washings have ceased to be greatly remunerative—which may even augment in productiveness as that of the sands declines. On the whole, then, although it is impossible to form any estimate of the actual amount of gold which year by year the great new mining fields are destined to supply to the markets of the world, yet we think two deductions may be assumed as perfectly certain from the facts we have stated—first, that the average annual supply for the next ten years is likely to be greater than it ever was since the commencement of authentic history—and second, that the supply, though the washings fall off, will be kept up for an indefinite period, by the exploration of the gold-bearing quartz veins in Australia and America.