SAJ'PlllKE IN UNrrKI) .STAIES. Ill 
( found ill the gravels that were eiubexhled hi the original matrix. Mr. 
Knuth, to whom I showed a specimen of the andesite containing sa])- 
phires from French Bar, said that it very closely resemhh'd the small 
fragments of rock carrying sai)i)hires that he had found at Kock 
Creek. It is not at all im})r()l)al)le that these sap])hires originated 
in the same type of rock as those of the Missouri Kiver and that 
small dikes of andesite will be found in the divide betweeii Myers. 
Cold, and Quartz creeks. A very few sapphires have been found on 
Quartz Creek. 
Although the sapphire gems from Rock Creek do not command so 
high a price as the rub}^ and the deep-blue sapphires, and are regarded 
more as fancy stones, they are coming to be quite highly prized by 
Uiany who are acquainted with them. As yet but fcAv of the Rocic 
Creek sapphires have been put on the market except locally at Helena. 
COTTONWOOD CREEK. 
The sapphire deposits on Cottonwood Creek are in Pow^ell County, 
about W miles southwest of Helena and 10 miles east of Deerlodge, 
the county seat. There has not been a great deal of work done 
on this creek, so that the extent of the sapphire-bearing gravels is not 
known. The sapphires are similar in character to those of Rock 
Creek, but they are apt to be of lighter color and not of such a 
variety of colors. Not sufficient Avork has been done at this locality 
to determine the importance of the deposits. 
:lll}ei 
YOGO GULCH. 
The sapphires that are the most widely known and that have 
attracted the most attention have been obtained in Fergus County, 
near the entrance of Yogo Gulch, on the Yogo Fork of Judith River. 
This locality is on the eastern slope of Prospect Ridge of the Little 
^™t Belt Mountains, about 75 miles northeast of Helena and 15 nules a 
little south of west of Utica, w-hich is the nearest town, and which is 
on the Judith stage line. The sapphires w^ere first found in the grav- 
1 els of Yogo Fork, and in following these up the creek their original 
source was located in dikes that extend across the country for a mile 
and a half.* The location of these deposits is shown in fig. IT. 
In PI. VII, x4, is shoAvn the appearance of the country in which 
'*' these mines are located. In the foreground is one of the shafts; it 
was started in 1897. 
There are two parallel dikes about 800 feet apart, with a general 
east-west trend, which vary in width from 15 to 75 feet. The miner- 
alogical com])osition of the rock shoAvs that it has a close affinity with 
minette and shonkinite, as described on page 47. 
lee 
c Weed, W. H., Twentietli Ami. Kept. I'. S. (Jeol. Survey, pi. .!. tS9!), pp. 4r>4-400. 
