60 ECONOMIC GEOLOGY 



metal is not present in sufficient quantity to warrant its extraction. 

 These auriferous copper ores are especially abundant in Colorado, 

 Utah, Montana and British Columbia. Also at Gold Hill, North 

 Carolina and in Newfoundland. 



The fourth class of gold ore is auriferous lead ores. The per- 

 centage of lead is large and the gold content often small. They 

 are refactory ores like the copper ores. By refactory ore is meant 

 one that requires roasting before amalgamation will take place. 

 The heavy sulphides as copper, lead and antimony require this 

 method of treatment, that is the condition of the gold in the min- 

 eral will not allow of its immediate union with mercury upon the 

 amalgamation plates. 



The fifth class of gold ores comprises the gold-telluride group. 

 The gold telluride ores occur with silver, or with silver, lead and 

 antimony, or as native gold accompanied by other tellurides. 

 These ores are often sent direct to the smelters for treatment. 



Geographical Distribution of Gold. Gold is widely distributed 

 in nature. It is present in almost all rocks, but only in a few 

 localities in sufficient quantity for profitable extraction. If a 

 line is drawn from Lake Winnipeg on the north southwesterly to 

 the eastern base of the Rocky Mountains and from thence 

 southerly to the Rio Grande River, nine-tenths of all the gold of 

 the United States lies west of that line. 



The American belt then may be divided into five areas : (1) The 

 Appalachian region, (2) the Black Hills region; (3) the Cordilleran 

 region; (4) the Pacific Coast belt, and (5) the Alaskan belt. 



Appalachian Region. The Appalachian field stretches in 

 a northeasterly direction from Alabama on the south, to New- 

 foundland on the north. It carries varying quantitites of gold. 

 The richest portion is in the southern part of the belt. Hundreds 

 of samples from this belt have shown traces of gold in almost all 

 cases. In the northern portion of the belt, at Newport, Vermont, 

 samples from Cambrian sericite schists have contained over $20 

 in gold per ton of ore. Near Lisbon, N. H., is found the best rep- 

 resentative of gold deposits in the northern half of the belt. 

 Samples containing more than $500 in gold per ton have been 

 assayed. A small mill is treating some of the ore but the output 

 is small. The ore occurs in a fissure vein traversing the crystal- 

 line rocks. The gangue is quartz, and in the upper portion of the 

 lode the associated pyrite has suffered much oxidation. 



The Southern Appalachian Field : The gold fields of the South- 



