188 Adventures in Scenery 



The zinc, lead, silver, and copper deposits as a rule are in lime- 

 stone, but the gold deposits seem closely linked to the granite, 

 occurring chiefly in the marginal zone of the granite masses or 

 in the immediately adjacent country rock. The primary ores 

 are probably genetically related to the granite intrusions. 



Source of Ores Deep-Seated in the Earth 



The source of the minerals gold, silver, lead, tungsten, cop- 

 per, and zinc is deep-seated. The primary ores are thought to 

 be genetically related to the granitic intrusions common in the 

 Inyo and Sierra ranges. The metals occur in veins, or asso- 

 ciated with intruded granitic rocks. The ultimate source is 

 the interior of the earth, and little is known of the character of 

 the deep interior from which the vast extrusions of molten 

 rocks have come. The gold of the Bishop Creek mine occurs 

 in a great quartz band or vein in sedimentary rocks that formed 

 part of the rock roof under and into which the great granitic 

 batholith was intruded. The gold deposits of the Inyo range 

 are mainly small, narrow quartz veins that occur either in the 

 borders of the granite intrusions or in the surrounding country 

 rock at no great distance from the granite. The lead ore of 

 the Cerro Gordo mine occurs in masses in a zone of marble, the 

 marble having been dissolved out and lead deposited in its place. 

 The primary ore is galena (sulphide of lead) . With it is asso- 

 ciated the sulphides of silver, copper, zinc, and iron. Zinc ore, 

 in the form of carbonate of zinc, replaces limestone (marble) 

 in the Cerro Gordo mine. 



Originally as all the zinc came from the depths of the earth 

 it came in contact with sulphuric acid and became zinc sul- 

 phide. By processes too complex to be discussed here the 

 sulphide was oxidized to zinc carbonate. All the metals are 

 deep-seated in their origin. Under the complex conditions 

 resulting from the up-welling of vast bodies of molten rock, 

 and the slow cooling of these extruded rocks, from the proc- 

 esses of metamorphism, and the circulation of waters through 



