ransomb.] DEPOSITS OF RED MOUNTAIN REGION. 225 
One of the most interesting and important facts in connection with 
the Guston, as well as with other mines of this district, is the change 
in character of their ores with depth. The galena ore of the main ore 
body, carrying from 50 to 60 per cent of lead and from 30 to 40 ounces 
of silver, continued down to the second level, ol* a little beyond, where 
it is said to have changed rather abruptly to high-grade stromeyerite. 
Galena, however, occurred in the mine in considerable quantities down 
to the fifth level, 288 feet in depth, and in decreasing amounts to 
greater depths. Some heavy galena, carrying from 100 to 175 ounces 
of silver, is known to have occurred at a depth of 212 feet. With 
increasing depth stromeyerite, or argentiferous chalcocite, became the 
characteristically rich ore of the mine, associated with pyrite and 
chalcopyrite. Some of tins was very rich, and in 1891 some ore from 
the sixtli level (378 feet) carried as much as 15,000 ounces of silver 
and 3 ounces of gold per ton. The lowest -grade ore in the deeper 
workings was pyrite, which usually carried less than 20 ounces of sil- 
ver and a fraction of an ounce of gold per ton, and from 3 to 5 per 
cent ol* copper, probably from admixture of chalcopyrite. The chal- 
copyrite was higher grade, usually carrying from L2 to 45 ounces of 
silver and a fraction of an ounce of gold per ton, and from 8 to 12 per 
cent of copper. Even in the best stopes of the fifth and sixth Levels 
there was always more or less chalcopyrite and pyrite associated with 
the rich stromeyerite, the Lower-grade ores apparently often prevail- 
ing on the peripheries of the Larger ore masses. 
Below the slip plane, which occurred just below the seventh level, 
at about 500 feet in depth, the ore was harder and more compact and 
stromeyerite was not found in any quantity, the ore down to the tenth 
level consisting chiefly of large masses of low-grade pyrite, with some 
bornite and chalcopyrite. The pyrite rarely carried as much as 20 
ounces of silver, with a little gold and copper. Some bornite found 
on the ninth Level (678 feet) carried from 125 to 450 ounces of silver 
and one-fourth to one-half ounce of gold per ton, with 25 to 50 per 
cent of copper. This was associated with chalcopyrite carrying 16 to 
75 ounces of silver and gold up to 1 ounce per ton, with from 8 to 15 
per cent of copper, and with pyrite carrying up to 15 ounces of silver 
per ton, with a little gold and copper. In both the ninth and tentli 
levels small quantities of ore were frequently met with carrying free 
gold, assays from level 9 giving as much as 29 ounces of gold per ton. 
The ore of the eleventh level was similar to that of the tenth, but, 
as in all these lower levels, the rich bornite bore a smaller proportion 
to the low-grade pyrite and chalcopyrite than did the stromeyerite and 
galena of the upper workings. The ore in the stopes connected with 
these levels varied in width from 18 inches up to 25 feet. Some free 
gold was seen in barite, associated with the bornite. On level 12 ore 
occurred in large solid masses, one being known to be 72 feet in length, 
Bull. 182—01 15 
