The extraction of gold from auriferous minerals by fusion, except as an incident in their treatment for other metals, is very rarely practised.
Gold is often present, and in many gold-mining districts the precious metal is obtained mainly from auriferous pyrites.
The principal rivers of Transylvania, which are either tributaries of the Theiss, or flow direct into the Danube, are: the Maros, which rises in the mountains forming the eastern wall of Transylvania, and taking first a northern course flows through the country from east to west; its principal affluents are the Gbrgenv, the Great and Little Kokel or Nagy and Kis Kiiki1116, the Strell (Sztrigi) and the Cserna on the left, and on the right the Ampoly and the Aranyos, which is rich in auriferous sediments.
Auriferous quartz is worked by a foreign company in its neighbourhood.
This expedition put an end to the hope, so long entertained, that it was possible to obtain a direct and practicable route for stock between Kimberley and Coolgardie gold-fields; and it also proved that, with the possible exception of small isolated patches, the desert traversed contained no auriferous country.
Auriferous sands, but not very rich, have been discovered in the feeders of Lake Hanka and the Suifong river, as also on the smaller islands of the Gulf of Peter the Great.
All these small rivers are described as auriferous and have attracted attention for this reason.
Theconglomerates are true " banket " and are auriferous, but the gold has not been met with in payable quantities.
Ac cording to Molengraaff it includes the two following series: - An upper group including the auriferous conglomerates of the Rand: Witwatersrand Series.
They may safely be considered to be among the oldest auriferous sediments of the world.
Thin bands of conglomerate, sometimes auriferous, occur near the base.
An auriferous district lies between the Nile and the Red Sea, in 22° N.
The whole range is highly auriferous, and the thickness of the strata is not less than 10,000 ft.
Modern methods of hydraulic mining have been introduced to work the auriferous banks of Poto; elsewhere antiquated methods only are employed.
The minerals of the second class, usually spoken of as " auriferous," are comparatively numerous.
(2) More common are the auriferous quartz-reefs - veins or masses of quartz containing gold in flakes visible to the naked eye, or so finely divided as to be invisible.
The genesis of the last three types of deposit is generally assigned to the simultaneous percolation of solutions of gold and silica, the auriferous solution being formed during the disintegration of the gold-bearing metalliferous veins.
The formation is noted for its regularity as regards both the thickness and the gold-tenor of the ore-bearing reefs, in which respect it is unparalleled in the geology of the auriferous formations.
So certain is the ore-bearing formation that engineers in estimating its auriferous contents feel justified in assuming, as a factor in their calculations, a vertical extension limited only by the lowest depths at which mining is feasible.
Water is poured on the dirt, and the rocking motion imparted to the cradle causes the finer particles to pass through the perforated bottom on to a canvas screen, and thence to the base of the cradle, where the auriferous particles accumulate on transverse bars of wood, called " riffles."
Disintegrating auriferous gravels by powerful jets of water, and the sluice system described above; in the second case the vein stuff is prepared by crushing and the amalgamation is carried out in mills.
The general conditions to be observed in such workings may be briefly stated as follows: (I) The whole of the auriferous gravel, down to the " bed rock," must be removed, - that is, no selection of rich or poor parts is possible; (2) this must be accomplished by the aid of water alone, or at times by water supplemented by blasting; (3) the conglomerate must be mechanically disintegrated without interrupting the whole system; (4) the gold must be saved without interrupting the continuous flow of water; and (5) arrangements must be made for disposing of the vast masses of impoverished gravel.
In working auriferous river-beds, dredges have been used with considerable success in certain parts of New Zealand and on the Pacific slope in America.
It was at one time proposed to treat the concentrated black iron obtained in the Ural gold washings, which consists chiefly of magnetite, as an iron ore, by smelting it with charcoal for auriferous pigiron, the latter metal possessing the property of dissolving gold in considerable quantity.
Many processes have been suggested in which the gold of auriferous deposits is converted into products soluble in water, from which solutions the gold may be precipitated.
One process depends upon the fact that, with a suitable current density, if a very dilute solution of silver nitrate be electrolysed between an auriferous silver anode and a silver cathode, the silver of the anode is dissolved out and deposited at the cathode, the gold remaining at the anode.
No auriferous reefs have been found.
Even the Calaveras man is no exception, since his skull and his polished conical pestle, the latter made of stone more recent than the auriferous gravels, show him to have been of Digger Indian type.
Other auriferous gravels are buried under the upland lava flows, and are now reached by tunnels driven in beneath the rim of the table mountains.
The development of the coal and iron interests, and the increasing importance of the gold product of the Appalachian auriferous belt, and also of the lead product of the Mississippi Valley, led to a more general and decided interest in geology and mining; and about 1830 geological surveys of several of the Atlantic states were begun, and more systematic explorations for the ores of the metals, as well as for coal, were carried on over all parts of the country then open to settlement.
In five years from the discovery of gold at Coloma on the American river, the yield from the auriferous belt of the Sierra Nevada had risen to an amount estimated at between sixty-five and seventy millions of dollars a year, or five times as much as the total production of this metal throughout the world at the beginning of the century.
The inland district watered by the Thames river is auriferous; Waitekuri (40 m.) and Karangahake (28 m.
Gold is found almost all over the region of crystalline rocks, except in and around the Antsihanaka province, the richest auriferous districts being a band of country parallel with the east coast and spreading at its southern end into the interior; and another tract, whose centre is about 100 m.
104) as of luxurious habits, wearing gold ornaments (the district is still auriferous) and having wives in common.
Traces of auriferous sands have been discovered at many places, but the percentage of gold is too poor to make the working remunerative.
Lead, wolfram, antimony and auriferous quartz exist in the districts of Coimbra, Evora, Beja and Faro.
Gold was washed from some of the Portuguese rivers before the Christian era, and among the Romans the auriferous sands of the Tagus were proverbially famous; it is, however, extremely improbable that large quantities of gold were ever obtained in this region, although small deposits of alluvial gold may still be found in the valleys of the Tagus and Mondego.
The district is both auriferous and coal-bearing.
The Witwatersrand series of the Transvaal includes auriferous conglomerates which have been worked since 1886 and constitute the richest gold-mines in the world.
The Yarkand-Darya and its numerous tributaries, which are fed by the glaciers of the mountain regions, as also many rivers which are now lost in the steppe or amidst the irrigated fields, bring abundance of water to the desert; one of them is called Zarafshan ("gold-strewing"), as much on account of the fertility it brings as of its auriferous sands.
29), with Sheba and Havilah, the latter also an auriferous country (Gen.
Only in the auriferous and civilized frontier districts of India (the Punjab) did a system of coinage find early acceptance.