kotlich.] ECONOMIC GEOLOGY GOLD. 145 



Gneissic scliists compose the country rock. It is distinctly bedded, and 

 its strata are cut at an acute angle, amounting to about 26° near the vein. 

 A shaft 105 feet in depth has been sunk on the vein. At a depth of 60 

 feet a drift has been cut toward the west. The width of the vein varies 

 from 1 foot to 4 feet. This is due to undulations in the hanging wall. 

 Yellow and white quartz composes the gangue, containing free gold 

 either in scales or as "fine gold." A mill with 20 stamps crushes the 

 ore obtained from this portion of the vein. It is said to run about $15 

 to 820 per ton; but richer ore is expected in some new openings. 



Miner's Delight. 



The middle portion of the vein has received this name. In its position 

 and associations it conforms to the Young America. A shaft 145 feet in 

 depth has been sunk, and some interior developments have been made. 

 At the time of my visit, buildings and machinery upon the surface had 

 been completed, and it was stated that work would soon be actively 

 resumed. 



Western Extension. 



This is the third portion of the entire vein. It is not worked at pres- 

 ent. Upon the vein a shaft has been sunk 100 feet in depth. A 20- 

 stamp mill located on the premises formerly crushed the ore, but now 

 lies idle. The character of the vein and ore remains constant throughout 

 the entire length, 1,600 feet. Occasionally pockets are found that pay 

 very well. To the depths which have at present been reached, the ore is 

 all more or less decomposed, yielding but little fresh pyrite. Some silver 

 enters the bullion, as I was informed. This, too, must be contained in 

 pyrite, as no specific argentiferous mineral is found in the vein. While 

 working from the surface, which was a cheap process, large quantities 

 of gold were taken from this lode. 



Reviewing briefly the character of the Sweetwater gold-mines, we find 

 that there are both true fissure veins and veins which form an integral 

 portion of the prevailing schists. The great age of the latter and their 

 physical structure has been the cause of extensive decomposition of the 

 ore downward. Water entering through joints and fissures, together 

 with atmospheric ah", have produced a conversion of the pyrite into 

 limonite, thus freeing the gold. From experience obtained throughout 

 this class of veins, we may say that the immediate surface-ores are 

 richer, as a rule, than those found at greater depths. So far as the 

 work in the various mines of this region extends, however, it appears 

 that even at considerable depths the ore contains a sufficiently high per- 

 centage of gold to make it remunerative if worked judiciously. I can 

 see no reason why, under proper management, and with an applica- 

 tion of experience gained elsewhere, many of these mines should not 

 prove to pay upon working. We may assume that the decomposed ores 

 extend to a depth of at least 150 feet. Their extraction and the process 

 of obtaining the gold out of them is both cheap and simple. In case the 

 ore should prove refractory lower down, methods are at hand to over- 

 come the difficulty. By crushing, concentrating, and amalgamating the 

 surface ores, good results ought to be obtained. Eventually roasting, or, 

 if the character of the ore should change, smelting may be employed in 

 the process of gaining the precious metal. For a number of years the 

 mines which may now be regarded as most promising can be worked 

 without much expense, as the location and class of ore at present ebinin- 

 ate nearly altogether the item of transportation. 



10 GS 



