240 GOLD - 



the primitive form has not been determined. The fracture is tine 

 hackly. It is soft, difficultly frangible, and malleable. The lustre 

 is splendent, and it does not tarnish on exposure to the air. The 

 specific gravity varies according to the quantity of alloy it contains, 

 from 12 to 19 or 20. It is sometimes nearly pure, but is generally 

 alloyed with small portions of silver and copper. It is distin- 

 guished from native copper by its greater density, and insolubility 

 in nitric acid ; and from copper pyrites, and iron pyrites, by its 

 specific gravity and malleability. 



Native gold occurs in veins, and disseminated in primitive and 

 transition rocks, more particularly granite and porphyry. It is 

 generally associated with quartz and felspar, and some of the ores 

 of iron, copper, silver, lead, cobalt, antimony, and nickel. It 

 occurs in gneiss and mica slate in Mexico ; in the latter in 

 Salzburg and the Tyrol; in quartz with needle ore, (acicular 

 sulphuret of bismuth,) and also in hornblende rock, at Schlangen- 

 berg, in Siberia. In the Bannat it occurs filiform and disseminated 

 in pale flesh red and greenish- white limestone, with white cobalt 

 ore and copper nickel. In the mines of Nagyag and Offenbauch, in 

 Transylvania, it principally occurs in clay-porphyry, grey wacke, and 

 greywacke slate. Gold is most commonly found in alluvial 

 deposits among sand in the beds of rivers, derived from the disin- 

 tegration of rocks in which it formerly existed. It is fonnd in 

 large quantities in the rivers and alluvial soil in many parts of 

 Africa, Brazil, Mexico, and Peru ; sparingly in the sands of the 

 Danube, the Rhine, and other European rivers. It is occasionally 

 found in the stream works in Cornwall ; in alluvial land in the 

 mining district of Leadhills, in Scotland, where, in the reign of Queen 

 Elizabeth, extensive works were carried on for the purpose of 

 collecting this precious metal. In the county of Wicklow, in 

 Ireland, gold has been found in a ferruginous sand, in masses of 

 considerable size. A rounded mass from this locality, in the 

 collection of the British Museum, is represented Plate 31, fig. 1. 



Sp. 2. Argentiferous Native Gold.— Electrum, Plin- 

 Hist. Nat. lib. xxxiii. cap. iv. p, 524 ; Elecktrum, Klaproth, b. 

 iv. s. 1. Its colour is pale brass-yellow, passing into silver-white. 

 It seldom occurs massive, generally in small plates, dentiform, or 



