56 



The elements associated with gold are silver, copper, mercury, 

 platinum, bismuth, iron, rhodium and tellurium. Gold occurs 

 also as an incrustation upon other minerals, and deposits on twigs 

 in the Hot Springs of New Zealand have been found. It has also 

 been detected as a cement joining fragments of quartz. These 

 occurrences all lead to the conclusion that secondary gold is de- 

 posited from solution, and that primary gold is of magmatic 

 origin (Figs. 39 and 40). 



Character of Ore Bodies. A very common occurrence of gold 

 is in true fissure veins, even and perhaps more abundant, in seams 



SIX FET 



FIG. 41. Gold Vein, Cripple Creek, Colorado. G, Granite; P, phonolite 

 A, altered, impregnated granite, with strings of fluorite and gold ore. 

 (After T. A. Richard, U. S. Geological Survey.) 



or layers in close proximity to the hanging wall, occasionally mi- 

 grating across the fissure vein and in close proximity to the foot- 

 wall. Fissure veins often fluctuate in value, so that the ore 

 richest in gold occurs in pockets, or "bonanzas" as the miner 

 says. In some mining belts one may by systematic drifting along 

 the direction of the main fissure vein encounter a "bonanza." 

 Where the normal concentration or value through the vein would 

 be from $6 to $10 per ton, a pocket might be represented by a 

 richness of $50,000 or even $100,000 per ton. It often occurs that 



