As already stated, gold mining is of two kinds, or rather the metal occurs in two different ways, each necessitating a particular kind of treatment to recover it. In the one case it is found in the form of a fine dust or grains, and to some extent as large nuggets, in the surface soil or débris, and it is gathered by washing such deposits in troughs called sluices with water. The gold by reason of its weight settles on the floor of the sluice, while the lighter gravel and sand are carried away. These are called placer or alluvial mines, and to this class belong the ancient fields of Asia Minor, the earlier Brazilian producing regions, the areas in California and Australia that yielded so enormously in the years between 1850 and 1860, and the Klondike and Nome deposits of Alaska of the present day.
Geologists tell us that the metal accumulated in these places during countless ages, as the result of erosion caused by rain, frost, heat, cold, glacial action, etc., operating on old granitic and schist rocks, in which occur veins, lodes, reefs and ledges (as they are variously termed) of quartz, which quartz is impregnated with particles of the yellow metal, or with crystals of ores of other metals, such as iron, copper and lead, that contain gold in a state of mechanical or chemical combination. And it is a fact that the deposits of each great alluvial field when followed up have led the explorer to areas of country (usually mountainous) where such quartz veins are found, and it is the exploration and working of these veins that constitute the other kind of gold mining, called quartz mining, which is the permanent form of the industry, and which is now in progress in America, Australia, South Africa, Mexico and India, and is coming slowly but surely into existence in Russia, Brazil, Alaska and Japan.
Alluvial or placer gold mining may be and generally is carried on with a very simple equipment. It is not a business that requires capital. With a pick, shovel, pan, some boards and nails, a hammer and saw and a few pounds of quicksilver, the energetic miner may start in business, and will rarely fail to make expenses and good wages. If he is one of the lucky ones, and gets hold of a rich piece of ground, he is rewarded with a fortune in a very short time.
On the other hand, after an alluvial field has been worked by the individual miner in his rather crude way, and is approaching exhaustion by his methods, it is common for a large number of claims to be consolidated under company or syndicate management and reworked. When this occurs systems of operation are inaugurated by which thousands of cubic yards of ground are washed daily, and modern capital may be advantageously employed in the creation and operation of the installations devised to accomplish the work. These consist of long ditches and pipe lines to bring in the water, lines of sluices in which to do the washing, dredges, elevating devices, undercurrents, etc. There have been built to date over 50,000 miles of ditches in California