GOLD. This metal is distinguished by its splendid yellow color ; its great density =19.3, compared to water PO ; its fusibility at the 82d degree of Wedge wood's pyrometer ; its pre-eminent duc tility and malleability, whence it can be beat into leaves only one 282,000th of an inch thick ; and its insolubility in any acid menstruum, except the mixture of muriatie and nitric acids, styled by the alchyinistc_4 aqua regia, because gold was deemed by them to be the king of me tals.
Gold is found only in the metallic state, sometimes crystallized in the cube, and its derivative forms. It occurs also in threads of various size, twisted and in terlaced into a chain of minute octahedral crystals ; as also in spangles or roundish grains, which, when of a certain magni tude, are called pepitas. The small grains are not fragments broken from a greater mass ; but they show by their flattened ovoid shape, and their rounded outline, that this is their original state. The spec. gray. of native gold varies from 13.3 to 17/. Humboldt states that the larg estyeita known was one found in Peru, weighing about 12 kilogrammes (261 lbs. avoird.); but masses have been, quoted in the province of Quito which weighed nearly four times as much.
' It is scattered over the whole globe in primary geological districts ; in the moun tains of Wicklow in Ireland ; in Lead hills, Scotland, and parts of Wales. In France, in the Valley of Oysecns, there is a vein of gold in quartz. Its aurife rous rivers are numerous. The Rhone, near Geneva, the Rhine, near Strasbourg, the Salat, Garonne, and the Herrault. The gold mines of Piedmont are still worked. It is worked at Salzbourg, in Germany, and also in Hungary and Transylvania. The Asiatic Ural chain contains many gold mines ; Africa pos sesses large auriferous deposits, chiefly alluvial. In South America, Brazil, Chi li, Peru, and Colombia, furnish produc tive quantities ofgold. It is found in Canada, Maine, Virginia, North and South Carolina, and California, in this continent. Along the Sierra Nevada, in this latter state, are found the chief sites of the gold diffused through the quartz mass. Along the Yuba, Trinity, San Jo
achim, Sacramento, and San Francisco, rivers, numerous rich placers have been found in the beds of the streams. There seems to be no limit to the extent of the quantity of gold diffused through the granitic rocks of this district, from which by attrition the streams have derived their gold. At Trinity Bluffs, the gold scales are found mixed with Basaltic sand, which 'so envelops and protects the gold that it is difficult to separate and purify the metal.
Auriferous sands require little treat ment to separate the gold. The sands are washed on a rocking table, and after wards in wooden bowls by hand. Amal gamation is employed to carry off from the sand the liglaterparticles of gold ; much of the California gold is obtained in this way. In some places the sand is so heavy as pot to allow the particles of gold to be separated, nor can acids be used, as lime and iron are present ; solu tion of chlorine from chloride of lime has been found to separate the gold ef fectually. In South Carolina the plan adopted is this :—The ore is crushed, by huge rotating iron rollers, during which a gentle fall of water carries the metal, as fast as it is pulverized, through a small aperture into a narrow trough, across which, at intervals, is a deposit of mer ,,ury. The trough is slightly inclined, by rhich means the sand passes out freely vhile the gold adheres to the quicksilver. At the close of the day this mercury, with the gold attached, is all taken out, and by a simple process called "pan ning," the metals are neatly separated. The mercury is bottled for re-use, and the gold is burned to eradicate the few particles of mercury which still adhere to it.
The other ores are metallic sulphurets, as those of copper, silver, arsenic, and iron. The following is an outline of the treatment of these :—The stony ores are first ground in the stamping mill, and then washed in hand-basins, or on wood en tables.