668 IDAHO MINING DISTRICTS. 



of boring show mainly granitic sand and clay, with nodules of iron 

 pyrite occurring at frequent intervals. The total thickness of the 

 lake beds would, then, be not less than 850 feet. A few miners'-inches 

 of saline water flowed from the well, as might indeed be expected, for 

 the geological conditions are such that a typical artesian basin is 

 formed. 



Gold in tine lake beds. It is stated that no gold is contained in the 

 lake beds or the false bed rock. This certainly seems, at first glance, 

 to be a strange state of affairs, considering that the sands, clays, 

 and gravels of the lake beds consist of practically the same material 

 as the auriferous gravels. It would seem, to imply^ that the quartz 

 veins from which the gold was derived were formed between the period 

 of the lake beds and that of the gravels. It will be shown, however, 

 that the lake beds are not entirely void of gold. Those just south of 

 the mouth of Granite Creek, shown in fig. 59, were prospected with the 

 pan. In the lowest bed, consisting of coarse gravel with much sand, 

 nothing was found; but 6 feet above the granite, in a finer gravel 

 admixed with some quartz pebbles, several colors were found in every 

 pan. The gold is extremely fine and of a rather pale color. There is 

 very little black sand in this gravel, but a considerable quantity of 

 monazite. The samples were taken under conditions that made it 

 impossible for any of this gold to have been derived from the rich 

 gravel above. Mr. Brockhausen informed me that in a claim one-half 

 mile below the mouth of Granite Creek a considerable amount of gold 

 was taken out of a bed of gravel dipping below the false bed rock. 



At the mouth of Noble Gulch, opposite Idaho City, there is a bed 

 of gravel a few feet thick dipping below strata of carbonaceous clay. 

 This gravel has been worked and is reported to have yielded some 

 gold. Mr. Barker informs me that a little gold may occur in the 

 gravels of the lake beds wherever quartz pebbles are present. Mr. 

 Kramer, who owns a claim one-half mile below Warm Springs, states 

 that John Wood, former owner of the claim, obtained good prospects 

 in a bed of gravel dipping under the false bed re k at that place. The 

 locality is now covered up. Mr. Turner states that nodules of pyrite, 

 containing a few dollars in gold and silver, are often found in the 

 false bed rock. During the sinking of the artesian well at Idaho City 

 certain strata were found to contain much iron pyrite, which upon 

 being washed out and assayed was found to carry as much as $12 per 

 ton in gold and silver. 



It is conceded, however, that these occurrences of pyrite do not 

 necessarily indicate an original content of gold in the lake beds, as 

 the precious metals may have been leached from the overlying rich 

 gravels and deposited with the pyrite below. 



It is thus certain that free gold occurs in some of the gravel of the 

 lake beds. That there could not be much of it present is clear from 

 the mode of formation of the lake beds, for they were deposited by 



