708 IDAHO MINING DISTRICTS. 



direction for 8 miles. The elevation ranges from 3,000 to 5,000 feet 

 above sea level. A ridge with northwesterly direction and culminat- 

 ing in Crown Point (elevation 5,300 feet) separates the two districts 

 and also the watershed of the Boise from that of the Payette. Most 

 of the mines of Willow Creek are located in the steep gulches at the 

 head of the North Fork of the same creek. On the eastern side a 

 steep descent leads down to Rock Creek, draining due northward into 

 the Payette. The eastern end of Rock Creek district lies on the north- 

 easterly trending ridge separating the Payette from the branches of 

 Shafer Creek. The mining towns of Pearl and De Levan are located 

 on Willow Creek. During the past summer there were probably 150 

 men in the districts. A small Huntington mill is erected on the 

 Easter claim, and two smaller custom mills are also built lower down 

 on Willow Creek. 



While placer deposits were worked in the vicinity of Willow Creek 

 long ago, and one of the mines of the district, the Red Warrior, was 

 worked in 1870, the majority of the locations have been made during 

 the past few years, especially in 1894 and 1895. The productive 

 mines of the districts are at present those in Willow Creek, and the 

 total output is probably about $80,000 in gold, all extracted within 

 the last few years. The output of 1896 is estimated at $50,000. 

 Among the producers are the De Levan group, the Checkmate, 

 Friday, Leviathan, Birthday, and Lincoln. 



GEOLOGY. 



GRANITIC ROCKS. 



The formation of chief importance as containing all the veins is 

 the granite and associated dike rocks. A few miles west of Pearl the 

 first granite hills emerge from under the cover of the Payette sand- 

 stones and rise rapidly eastward, extending thence uninterruptedly 

 in a northeasterly direction. The larger part of the area is occupied 

 by a granitic rock, which is a local modification of the normal granite 

 of the Boise Mountains. 



The rock crumbles and disintegrates very easily, and the slopes of 

 the mountains are covered by a deep mantle of disintegrated rock. 

 During the winter rains the erosion goes on very rapidly, and deep 

 gulches are often excavated in a remarkably short time. It is possi- 

 ble to obtain the fresh rock only from exposures in the bottom of the 

 canyons or in prospect tunnels. The rock is of a light-gray color and 

 has a coarse-grained structure, the average grain having a diameter 

 of from 3 to 6 mm . It is composed of white feldspar, quartz, biotite, 

 and sometimes hornblende. Brown titanite in small grains is uni- 

 versally present. Occasionally larger grains of light-red orthoclase 

 appear among the prevailing white plagioclase. Under the micro- 

 scope the following minerals are noted : Hornblende appears in brown- 



