GEOLOGICAL SURVEY OF THE TEEEIT0RIE3 209 



At Idaho there is a hot soda spring-, whose waters, however, I did not 

 analyze. Jiist, above Idaho is a skiice which once upon a time washed 

 out one ounce of gold (twenty-three dollars) per hand per diem, hut the 

 best is now washed out. Near Seven-mile bridge the gneiss i^itches 

 almost vertically on the right baiik of the creek, and resting upon these 

 upturned basset edges were huge masses of gray granite. 



GEOEGETOWN. 



The characteristic mineral of the country is zincblende, associatetl with 

 galena, iron pyrites, and comparatively little copper pyrites. The most 

 usual gangue rock is decomposed i^orphyry, and decomposed granite, 

 with much quartz. The country rock is composed mainly of gneiss. In 

 West Argentine there is considerable lluor spar occurring, as gangue 

 rock. 



Baiter lode. — So far as an approximation to an average dip could be 

 got, this appeared to be east northeast, but throughout the region the 

 rocks are huddled together with such irregularity that nothing definite 

 can be stated about either the general dip or the general strike of the 

 rocks. The general strike of the veins is east of north, and their pitch 

 nearly vertical. 



Broivn lode. — At most of the mines the ore is got out by hoisting, but 

 at this one there is a tunnel driven in sixteen hundred feet above the 

 bed of the creek to intersect the shaft. The mouth of this latter is one 

 hundred and ten feet above the tunnel, and is met by the above-mentioned 

 cross-cut, (one hundred and eighty feet long,) and by a drift extending 

 (up to the date of these notes) but thirty feet out from it. The ores found 

 in the Brown lode are native (wire) silver, antimonial silver, (AgSbs,) 

 stephanite, copper-fahlerz, polyl3asite, and the dark and light ruby ores. 

 The amalgamation works below here are usually supplied with ores con- 

 taining less than five i>er cent, of lead. 



An engine of thirty horse-power drives the machinery of the mill, 

 and in 'winter time warms the water intended for the wet stamps, and 

 the building itself, by means of a steam-i)ipe leading to the tank con- 

 taining the water. The mines are not troubled by water. In last April 

 the miners had some trifling difiiculty to contend against after the spring 

 thaw 5 but this was promptly met and overcome. There are twenty 

 stamps for wet crushing and four others each of 500 pounds weight. The 

 ore contains about twenty per cent, lead, but this is insufficient to meet 

 the wants of the furnace, and lead is bought to supply the deficiency. 

 Thirty-five per cent, of lead is necessary to the carrying on of the pro- 

 cess. There are two classes of ore which are dressed or separated by 

 hand. The first-class'^ore is crushed dry and goes directly to the furnace. 

 The second-class ore is crushed wet, and dressed by means of a circular 

 buddle revolving from fifteen to twenty times per minute. Under one 

 huntlred ounces per ton, the ore is not treated, but is dumped out and 

 saved in the hope that the reduced price of labor or some more econom- 

 ical process may enable the owners to work it to advantage.* 



The ore, after having been dressed and sorted as above-mentioned, is 

 mixed with ten per cent, lime and fifteen per cent, iron, and is subjected 

 to a low red heat in a reverberatory furnace to reduce any argeutiferous 

 litharge that may be present. Then high heat is given, and the sulphide 

 is converted into argentiferous lead and matt, according to the usual 

 method. 



* One per cent, silver equals abotit tliree hundred ounces i^er ten, so that one hundred 

 ounces per ton equals one-thii'd of one x)er cent. 



14 H 



