LIXDOKKN.] DEPOSITS OF BLACK HORNET MINING DISTRICT. 705 



and a drift following the hanging wall north. A width of several 

 feet of quartz is shown, and near the northern end of the claim a pay 

 shoot exists 100 feet long and said to be 9 feet wide, carrying an ore 

 which averages $15, of which about half is in free gold. The ore is 

 is similar to that of the Ironsides. The Ironsides or Black Hornet 

 adjoins on the north, and its principal pay shoot lies near the line of 

 the Viola claim. It is developed by a cross cut striking the vein 

 about 100 feet below the croppings and a winze sunk 100 feet deep 

 ear the southern end-line in the drift. The pay shoot extends 200 

 feet north from the end line, but only 70 feet of it consists of shipping 

 ore. Along the pay shoot the quartz reaches a width of 10 feet or more. 

 This block of ore between tunnel level and surface was stoped and 

 shipped, averaging, it is said, $40 per ton, almost entirely in gold. 



North of the richest pay shoots are large amounts of lower-grade 

 ore. The vein shows as a body of massive, fine-grained white quartz, 

 from 2 to 10 feet wide, and contains sulphides irregularly distributed 

 through it. The sulphides, which in the pay shoot will amount to 8 

 per cent of the ore, consist of arsenopyrite, pyrite, and zinc blende. 

 The value is by no means exclusively in the sulphides, for a specimen 

 of massive zinc blende and arsenopyrite assayed only 0.40 ounce of 

 gold and 4.60 ounces of silver; a total value of $11.50. A sample of 

 the quartz with scattered iron pyrite yielded 0.45 ounce of gold and 

 1 ounce of silver; a total value of $10. The walls are often ill defined 

 and without a clay selvage, and consist of shattered granite and 

 granite-porphyry altered by thermal processes. The feldspar is 

 largely converted to sericite or white mica, and the rock contains, for 

 a few feet on each side of the vein, much scattered arsenopyrite. 

 This altered wall rock contains, in strong contrast to the filling, only 

 a trace of gold and silver. The Ophir vein lies one-half mile north 

 of Ironsides and has a similar direction. But little work has been 

 done on it. Near the Ophir vein a long vein begins, and extends, 

 with a westerly dip, due north across Dead Dog Creek to Deer Creek. 

 The following claims are located on it, beginning at the southern 

 end: Mclntyre, Gray Eagle, Sorrel Horse, Golden Rule, and Montana. 

 Most of them are but superficially developed, and the ore, though 

 free milling on the surface, grows base at a slight depth. The Mon- 

 tana is opened by a cross cut 270 feet long. 



BOISE MINING DISTRICT. 



At a distance of from 3 to 5 miles east and east-northeast from 

 Boise are a number of prospects which have never produced much, 

 yet are worthy of mention. The country rock is normal granite 

 throughout, cut by a few dikes of granite-porphyry with a general 

 north-northwesterly direction. Dikes of dark lamprophyric rocks 

 also occur. 



18 GEOL, PT 3 45 



