494 MINING INDUSTET. 



that crowd the surrounding hills. To describe all these lodes, and the mines 

 opened upon them, would be impossible, within reasonable limits, and a mere 

 enumeration of them would be useless. It may suffice, therefore, for the pur- 

 poses of this chapter, to select typical veins for description, choosing those 

 that have been most extensively worked, since they afford the largest oppor- 

 tunity for observation in depth and length, and, at the same time, furnish the 

 most characteristic illustrations of the general method of development. 



Concerning these lodes in general, it may be said that they are all in- 

 closed in rock which is of one common type, chiefly granitic, with some 

 gneissic varieties. They possess a high degree of parallelism in their strike 

 or direction ; their course, with few exceptions, being between due east and 

 west on one hand, and northeast and southwest on the other. Within these 

 limits the prevailing direction or course, among the prominent lodes, is nearly 

 due east and west, or from 5° to 10° north of east. The Gregory, Bates, 

 and a few others are exceptions to this statement, but the Bobtail, Burroughs, 

 Gardner, Flack, Gunnell, Winnebago, and others, strike about north 85° east, 

 and represent, more nearly than those before mentioned, the average course 

 of veins in the district. The dip of the lodes is generally at a high angle, or 

 nearly vertical. They possess the distinctive features of true fissure veins, 

 and they are remarkably free from faulting or displacements. 



In the following pages some of the most noteworthy lodes, which, in 

 many respects, may serve as representatives of the others, will be described, 

 with the view of presenting to the reader the characteristic features of the 

 veins and the mode of occurrence of their ores; the manner in which the 

 mines located upon them are developed, with some details concerning the cost 

 of mining, the value and yield of the ores, and the relation of cost to pro- 

 duction. 



The latter part of the chapter will include a description of the principal 

 methods of treating the ores, and some statistical information concerning the 

 operations of stamping mills ; the cost of milling and other metallurgical treat- 

 ment; the relation of assay value to the yield of the ores, and a statement of 

 the bullion production of the district. 



Bobtail Lode. — The Bobtail lode has the reputation of having been the 

 most productive vein of Colorado and of still producing the richest gold ores. 





