20 On the Geological Distribution of Gold. 



Mineral and Metallic compounds contained in Auriferous 

 Veins. — Gold, always in a metallic state, occupies a limited 

 number of rocks, usually quartz filling tlie fissures, and generally 

 forming the gang or vein producing gold. But well-known 

 exceptions have been noticed in S. America, wbere bi-sulphuret 

 of iron forms the gold- producing veinstone, associated with 

 some quartz and other minerals, in a comparatively small 

 proportion. It is now an established fact that pyrites will 

 always show traces of gold, and in some instances prove very 

 rich; but what is not generally known, is the following truth, 

 viz., that the bi-sulphuret of iron rarely exists alone with gold, 

 some other auriferous matter being involved in the pyrites 

 which carries the gold. This fact gives consequently a fair ex- 

 planation why auriferous pyrites is difficult to reduce in aperfect 

 and profitable manner. To convert the black oxide of iron 

 into a red oxide is certainly the step required for separating 

 gold-particles involved in the pyrites ; but when we see that 

 this metal is associated with some other compound, any opera- 

 tion that might eliminate or free the gold from the pyrites, 

 will be found insufficient — this, many vain efforts have proved, 

 and very reasonably so, from the fact alluded to. Bi-sul- 

 phuret of iron is, therefore, the most difficult, and quartz the 

 easiest of all gold-bearing minerals capable of being reduced 

 so as to separate the gold. 



Quartz, carbonate of lime, rarely sulphate of lime, ferru- 

 ginous lime, argillo-ferruginous compounds, also clay 

 in its plastic state, fluor-spar, sulphate and carbonate of 

 baryta, schorl, tourmaline, chlorite, &c., are also found in 

 auriferous veins. 



Quartz being the most prevailing of minerals in which 

 gold is contained, has received the title of its matrix. In cal- 

 careous minerals, in schorl, and tourmaline, gold has not 

 been seen, at least in South America. 



Metallic compounds occupying auriferous veins, being 

 auriferous. — Bi-sulphurets of iron, lead, silver, and copper, 

 green carbonate of copper, mixed copper and iron-ores, tel- 

 lurium, arsenical-iron, earthy carbonate of lead, and 

 chloride of silver. Per-oxide of iron, with silica and clay, in 

 an indurated and foliated state, specular iron-ore, and hydrous 

 oxide of iron. Of these compounds, the pyrites, the bi- 

 sulphuret of lead, the silico-argillaceous compounds, and the 

 hydrous oxide of iron are the most prevailing, nextto the quartz. 



The following general conclusions seem to be adopted all 

 over the world, viz.: — the sides or backs of veins pro- 



