weed] GOLD MINES OF MARYSVILLE DISTRICT, MONTANA. 89 
The veins. — The geologic map which was rjrepared in the summer of 
1901 shows that the veins occur either in close proximity to the granite 
contact or adjacent to the intrusive dikes. The vein systems devel- 
oped near the town of Marysville show three distinct directions. The 
northeastr-system, exemplified in the North Star vein, cuts through the 
sedimentary rocks and into the granite. The northwest system is 
prominent in the granite area, but has not produced any large ore 
bodies. The north-south system is the one to which the Drumlum- 
mon lode belongs, and at the Drumlummon mine is parallel to the 
granite contact. The ores occur in fissure veins, showing a distinct 
quartz filling, either as a solid mass or enveloping angular fragments 
of the country rock. The Drumlummon vein is the best known and 
may be taken as a type. It is a fault plane with white opaque quartz 
inclosing angular fragments of black, green, and drab slates, which 
are sometimes distinct and unaltered and at others have been much 
decomposed. Where the ore bodies are found the replacement has 
been complete and the former presence of the fragments is only recog- 
nizable by the outlines of the banded quartz. The vein has distinct- 
walls, which are rather wavy and vary from 2 to 20 feet apart. South- 
ward the Drumlummon vein itself splits into several branches. It 
has been developed for a distance of about 3,000 feet horizontally and 
to a depth of 1,600 feet, but no ore was found below the 1,000-foot 
level. This vein, which is the largest and the most productive in 
the district, consists in its lower levels of a mass of angular rub- 
bish, derived from the walls of the fissure, and in places cemented by 
quartz, in other places still retaining its original character. Com- 
pared with the Empire and other veins, it is much more extensive, 
both laterally and vertically, and the values have gone deeper. In 
general it may be said that all the veins of the district carry rich 
ores in bonanzas and ore shoots within the first 200 feet from the 
surface, but that in depth the ores rapidly decrease in value until 
the vein is no longer workable. It may also be said that the ore 
shoots were well defined, and the intervening vein matter barren 
and unworkable. The pitch of the ore shoots conforms to the usual 
habit, dipping to the right when looking down the dip of the vein. 
The ores consist of sulphides and sulphantimonides of silver, with 
gold aggregating 60 per cent of the total value. In the upper levels 
the ore is somewhat oxidized, and in the ore shoots of the Drumlum- 
mon mine carried extremety high values. In the Bald Butte mine 
the larger veins are clear instances of filled fissures with but little 
evidence of replacement, and the new vein recently opened contains 
a streak a few inches wide of soft ore whose value is extremely high. 
Recent attempts have been made to open up some of the large prop- 
erties which have been idle for many years. The Empire mine, par- 
ticularly, has been opened and new development work begun. There 
seems reason to believe that with the low rates of treatment now 
available many of these properties may be reopened and worked. 
