Gold prospectors have noted the influence and importance of the mineralogical properties of gold in different deposits and specifically in its occurrence. For instance, gold may be found in veins, in pyrites, in granite rocks, and in layers or strata of clay, gravel and pebbles, sometimes at a considerable distance below the soil. It is also obtained in considerable quantities mixed with sand and gravel on the surface. In North America it exists in loose deposits in beds of gravel from 20 cm to 90 cm in thickness, and from 80 to 180 cm from the surface of the ground. In California, it consisted chiefly of alluvial gold; in Australia gold quartz, a semi-crystallized rock, chemically termed hydrate of silicon, is more common, the precious metal in these lumps of rock appearing in the form of branchlike fragments. Here it is also found in some abundance in various-sized nuggets, and more plentifully in the form of gold-dust.
Gold-dust abounds chiefly in the sands and beds of rivers. On the coast of Africa, it is said that the people dug out the earth, rich in gold-dust, to a great depth. In Ireland gold was found in masses, some lumps being of great size. The nuggets found in Australia often exist in large masses, one specimen having been found weighing 46 ozs. The mines of Russia contained large masses of gold; on the southern portion of the Ural Mountains (Asiatic side). In 1842, sands of immense richness were discovered; and at the period of an enormous mass of gold were dug up weighing about eighty pounds. This splendid mass was afterwards placed in the collections of the Corps des Mines, at St. Petersburg. Some years later it was found in the same neighborhood, other nugget. According to some experienced gold prospectors, it is not, however, a usual thing to find masses of such proportions in; the metal more commonly existing in small grains or fragments, and the yield averaging from thirty to seventy grains of gold per ton of soil.
In Australia, one of the great modern gold-producing countries, massive lumps are to be found in considerable quantities. There are several ways of separating the gold from the ore at the different deposits throughout the world. The simplest method is that of washing the sands of rivers, which are the alluvial deposits which have been washed by floods and storms into deep gullies. As a consequence, there were developed numerous processes of washing based on the mineralogical properties of gold and gold-bearing minerals, and these are adopted to suit the resources of the gold-diggers. In America, and other countries having sands rich in gold-dust, this washing may be performed in shallow pans; the earth being put in and well stirred up with water, the light earthy matters suspended in the water being afterwards poured away from the gold. This process is repeated until all the particles of earth are removed, leaving the gold-dust visible to the naked eye in minute grains at the bottom.
Another method which found some favor amongst gold-diggers, was the employment of shallow troughs, lined with coarse cloth at the bottom; these troughs, which are of some length, were placed in a slightly-inclined position; the auriferous sands are then thrown into the trough, a gentle stream of water is allowed to run in, and from its inclined position, the fine sand is washed away, leaving behind the small particles of gold in the tissues of the cloth, which are recovered by washing in water. In other cases, ordinary sloping boards, of common deal in its rough state, are taken, and shallow grooves made across them; the soil is then thrown upon the planks, the coarseness of which, together with the grooves, form collecting -places for the gold, which, on account of its very high specific gravity, sinks into the crevices thus provided, while the lighter matters are washed away by the stream of water employed for the purpose.
