The first permanent settlements in Matto Grosso seem to have been made in 1718 and 1719, in the first year at Forquilha and in the second at or near the site of Cuyaba, where rich placer mines had been found.
Abandoned placer mines are to be found in every part of the unsettled interior, showing how thoroughly it had been explored by goldhunters in those early days.
The term 1 is not limited to underground operations, but includes also surface excavations, as in placer mining and open-air workings of coal and ore deposits by methods similar to quarrying, and boring operations for oil, natural gas or brine.
For the special methods by which placer deposits are mined see Gold.
The gold is found in placer deposits.
The gold production of Russia has been remarkably constant, averaging £4,899,262 per annum; the gold is derived chiefly from placer workings in Siberia.
In the placer or alluvial deposits, the precious metal is found usually in a water-worn condition imbedded in earthy matter, and the method of working all such deposits is based on the disintegration of the earthy matter by the action of a stream of water, which washes away the lighter portions and leaves the denser gold.
Gold exists and many native villages have small "placer" mines.
About nine-tenths of the gold was got from dry or siliceous ores and about 8% from placer mines; about twothirds of the silver from dry or siliceous ores, about two-ninths from copper ores, and most of the other ninth from lead ores.
Helena was established as a placer mining camp in 1864 upon the discovery of gold in Last Chance Gulch.
The washing of the high or Tertiary gravels by the hydraulic process and the working of mines in the solid rock did not, on the Gold and whole, compensate for the diminished yield of the Silver ordinary placer and river diggings, so that the product of gold in California continued to fall off, and by 1860
In early days the placer gold mines of the Columbia, Fraser and Caribou attracted miners from everywhere, but these have declined, and lode mines supply most of the gold as well as the other metals.
Placer gold was found at the mouth of the creek in 1879, and the city was settled in 1880 by two prospectors named Joseph Juneau and Richard Harris.
The placer-miner's cradle and rocking-trough were replaced by puddling troughs stirred by a revolving comb worked by horse power; reservoirs were constructed for the scanty water-supply, bucket elevators were introduced to carry away the tailings; and the natives were confined in compounds.
The continual poverty which hindered the successful prosecution of the war against the Hussites, and which at times placer Sigismund in the undignified position of having to force himsel, as an unwelcome guest upon princes and cities, had, however, one good result.
In 1885 the rudest process of "placer" washing produced an export of gold dust amounting to 120,000 pounds; quartz-mining methods were subsequently introduced, and the annual declared value of gold produced rose to about 450,000 pounds; but much is believed to have been sent out of the country clandestinely.
It is almost wholly in the form of snow; and this snow, melting in summer, is of immense importance to the state, supplying water once for placer mining and now for irrigation.
Gold was discovered on the Sweetwater river in 1867, and placer and quartz deposits have been found in almost every county in the state.
There are a great many placer washings, among which are some extensive deposits near the Straits of Magellan.
In Idaho, as elsewhere, the first form of mining was a very lucrative working of placer deposits; this gave way to vein mining and a greatly reduced production of gold and silver after 1878, on account of the exhaustion of the placers.
Placer gold was discovered on an affluent of Boulder Creek in January 1859.
In the south and south-west provinces placer gold mines by the banks of watercourses are worked by Gallas as an industry subsidiary to tending their flocks and fields.
Part of Oregon in 1852, and placer-mining was prosecuted here without interruption until 1860, when the metal was found in larger quantities on the streams in Baker and Grant counties in the north-eastern part of the state.
Quartz-mining has since very largely taken the place of placer-mining, but the two principal gold-producing districts are still that traversed by the Blue Mountains in the northeastern quarter and that drained by the Rogue river in the southwestern corner, a continuation of the California field.