686 



IDAHO MINING DISTRICTS. 



relatively. While this is possible, the probabilities are strongly in 

 favor of an overthrust. 



Tlie Gambrinus (Surprise] vein. This large deposit is situated 5^ 

 miles north-northeast of Idaho City, on the summit of the ridge 

 between Elk and Moore creeks and near the foot of the steep Forest 

 King Hill. The elevation is 5,480 feet. It was discovered in 1864, 

 and the principal work was done between 1864 and 1865. The total 

 production is $263,000. The strike of the vein is N". 61 W., and the 

 dip, measured on the exposed foot wall, is 45 S. It can be traced for 

 some distance westward, and the Buckeye forms the western exten- 

 sion. The vein has a maximum width of 40 feet, and isjof the same 

 composite type as the Illinois, consisting of a sheeted zone in granite 

 with a great many small and rich quartz seams between the joints, 

 these seams containing all the pay. The surface is very greatly 

 decomposed arid has been extensively sluiced. Two chimneys or 

 shoots of rich ore were found close together, dipping east on the plane 

 of the vein, at first steep and then more gentle. These shoots were not 



nearly so long as the Illi- 



Norfh 







r 



^ 



Vein 



^. 



Vein 



rOrifr 



7 



FIG. 62. Diagram of fault in the Cleveland vein. 



nois ore body, but richer. 

 The ore contains antimo- 

 nite, and this mineral ap- 

 pears to be closely associ- 

 ated with the gold. The 

 vein has been developed 

 only by short tunnels and 

 small shafts, riot over 100 

 feet deep, and appears, 

 like the Illinois, to deserve 

 much more extensive pros- 

 way of water and heavy 



pecting. The same difficulties in the 

 ground will probably be met with in depth. 



The Boulder vein. This deposit is located on Elk Creek, 6 miles 

 north by east of Idaho City, at an elevation of 4,830 feet. Prepara- 

 tions were made a few years ago to exploit this vein on a large scale, 

 and an excellent 30-stamp mill, to be driven by water power, was 

 built. It was run for only a short time, the ore probably being of 

 too low grade to handle profitably; neither was there much ore in 

 sight, so that it would have been necessary to sink below the creek 

 level almost immediately. The vein, which crops for only a short 

 distance and is marked on the canyon slope by quartz croppings sev- 

 eral feet thick, strikes on the surface N. 75 W. and dips 50 S. It is 

 opened by a tunnel 900 feet long. The general character is the same 

 as the Gambrinus and the Illinois, being a very wide (up to 40 or even 

 60 feet) zone of sheeted granite filled with many small seams of quartz 

 carrying pyrite, arsenopyrite, and zincblende scattered through it. 

 As it was necessary to mine the whole width, though the pay was 



