While, therefore, it is certain that the new American and Australian diggings will individually, or on each spot, become poorer year by year, yet, as in Siberia, the extension of the search, and the employment of improved methods, may not only keep up the yield for a long period of years, but may augment the yearly supply even beyond what it has yet been.
But while so much uncertainty attends the consideration of the extent, richness, and durability of mines situated in the gold-bearing sands and gravels, something more precise and definite can be arrived at in regard to the gold-bearing rocks. In nearly all the gold countries of past times, the chief extraction of the precious metal, as we have said, has been from the drifted sands. It is so also now in Siberia, and it was naturally expected that the same would be the case in California. And as other countries had for a time yielded largely, and then become exhausted, so it was predicted of this new region, and it was too hastily asserted that the increasing thousands of diggers who were employed upon its sands must render pre-eminently shortlived its gold-bearing capability. This opinion was based upon the two considerations—first, that there is no source of reproduction for these golden sands, inasmuch as it is only in very rare cases that existing rivers have brought down from native rocks the metallic particles which give their value to the sands and gravels through which they flow—and second, that no available quantity of gold was likely to be found in any living rocks.
But in respect of the living rocks, two circumstances have been found to coexist in California, which have not been observed in any region of gold-washings hitherto explored, and which are likely to have much effect on the special question we are now considering. These two circumstances are the occurrence of numerous and, it is said, extensive deposits of the precious metals in the solid quartz veins among the spurs of the Sierra Nevada, and of apparently inexhaustible beds of the ores of quicksilver.
The discovery of gold in the native rock was by no means a novelty. The ancient Egyptians possessed mines in the Sahara and other neighbouring mountains. “This soil,” says Diodorus, “is naturally black; but in the body of the earth there are many veins shining with white marble, (quartz?) and glittering with all sorts of bright metals, out of which those appointed to be overseers cause the gold to be dug by the labourers—a vast multitude of people.”[[18]]
At Altenberg also, in Bohemia, in the middle ages, the mixed metals (gold and silver) were found in beds of gneiss;[[19]] and, at present, in the Ural and Altai, a small portion of the gold obtained is extracted from quartz veins, which penetrate the granite and other rocks; but these and other cases, ancient and modern, though not forgotten, were not considered of consequence enough to justify the expectation of finding gold-bearing rocks of any consequence in California. It is to another circumstance that we owe the so early discovery of such rocks in this new country, and, as in so many other instances, to a class of men ignorant of what history relates in regard to other regions.
As early as 1824, the inner country of North Carolina was discovered to be productive of gold. The amount extracted in that year was only 6000 dollars, but it had reached in 1829 to 128,000 dollars. The washings were extended both east and west, and finally it was made out that a gold region girdles the northern part of Virginia, the two Carolinas, and Georgia. This region is situated towards the foot of the mountains, and where the igneous rocks begin to disturb and penetrate the primary stratified deposits. As the sands became poorer in this region, the ardent miners had followed up their stream-washings to the parent rock, and in veins of rusty quartz had discovered grains and scales of native gold. To obtain these, like the Africans at Semayla, they blasted, crushed, and washed the rock.
Now, among the first who, fired by fresher hopes, pushed to the new treasure-house in California, came the experienced gold-seekers from the Carolinian borders. Following the gold trail into the gulches and ravines of the Snowy ridge, some of them were able to fix their trained eyes on quartz veins such as they had seen at home, and, scattered through the solid rock, to detect sparkling grains of gold which might long have escaped less practised observers. And through the same men, skilled in the fashion and use of the machinery found best and simplest for crushing and separating the gold, the necessary apparatus was speedily obtained and set to work to prove the richness of the new deposits. This richness may be judged of by the following statements:—
“Some of the chief quartz workings are in Nevada and Mariposa Counties, but the best known are on the rancho or large estate bought by Colonel Fremont from Alvarado, the Mexican governor. They are those of Mariposa, Agua Fria, Nouveau Monde, West Mariposa, and Ave Maria—the first leased by an American company, the third by a French, and the others by English companies. Some of the quartz has been assayed for £7000 in the ton of rock. A Mariposa specimen was in the Great Exhibition.
“The Agua Fria mine was surveyed and examined by Captain W. A. Jackson, the well-known engineer of Virginia, U.S., in October 1850, for which purpose openings were made by a cross-cut of sufficient depth to test the size of the vein and the richness of the ore. The vein appears to be of a nearly uniform thickness—of from three and a half to four and a half feet—and its direction a few points to the north of east; the inclination of the vein being 45°. Of the ore, some specimens were transmitted to the United States Mint in January 1851; and the report of the assays then made, showed that 277 lb. of ore produced 173 oz. of gold—value 3222 dollars, or upwards of £650 sterling; being at the rate of £5256 a ton.
“The contents of the vein running through the property, which is about 600 feet in length, and crops out on a hill rising about 150 to 200 feet above the level of the Agua Fria Creek, is estimated at about 18,000 tons of ore to the water level only; and how far it may descend below that, is not at present known.