GOLD MINES OF THE MARYSVILLE DISTRICT, MONTANA. 
By Walter Harvey Weed. 
The Marysville mining district is the most important producer of 
the precious metals in the State of Montana, one mine alone having 
yielded a total of nearly 115,000,000, while the aggregate production 
of the mines of the district has been roughly estimated at double that 
figure. The district is located 18 miles northwest of Helena, and is 
reached by a branch railroad running north from the main line of the 
Northern Pacific Railway. The Great Northern Railway runs a few 
miles east of the district. The district comprises a mountainous 
country traversed by the continental divide, a few of the mines being 
on the western or Pacific slope. The development of the region began 
in the early seventies, the rich placer diggings of Silver Creek leading 
to the discovery of the ledges which have made the region famous. 
Although within its area there have been many productive mines, as 
a rule the values have been in rich ore shoots, and after these were 
exhausted the property has been abandoned. The most famous prop- 
erty of the district is undoubtedly the Drumlummon mine, which has 
yielded a larger amount of gold than any other mine in the State. A 
later discovery, the Bald Butte mine, has been steadily worked for 
many years, one year's dividends approximating the total amount of 
capitalization. At the present time the Bald Butte is the only mine 
actively worked, and the district therefore may be said to be in 
decline. 
Geologic features. — The Marysville district consists of a central 
mass of granitic rock surrounded hy slaty shales and thin-bedded 
argillaceous sandstones. The granitic rock is probably part of the 
great granite area which underlies so much of the western portion of. 
Montana. The rock is technically a quartz-diorite of even and coarse 
grain, showing little variation in appearance or mineralogic develop- 
ment. The shaly rocks into which this diorite has been intruded 
belong to the Belt terrane and consist of a thickness of many thou- 
sand feet of thin-bedded argillaceous rocks. Near the granite con- 
tact these rocks are altered to hard and dense hornstones, while 
farther away they show a slaty fracture, the laminae corresponding, 
however, to the bedding planes. Outside of the district proper, to 
the south and west, the Cambrian and later sedimentary rocks 
appear. There are a few dikes of acidic porphyry and of dark trap 
rocks which cut the granite near its borders and penetrate the sedi- 
mentary rocks. These are especially abundant near Bald Butte. 
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