Very little metallic mineral development has occurred in the Snow Crest - Greenhorn mining district in southwest Madison County. As with other similar districts with little mineralization, the Snow Crest - Greenhorn district serves to separate other more developed districts.
Structurally, the Greenhorn Range is the northwest limb of a large syncline, the axis of which plunges to the southwest. The most abundant rock type in the range is quartzofeldspthic gneiss. Several small ultramafic bodies, now partly serpentinized, are exposed. Post-metamorphic granite and pegmatite dikes are abundant in the northern part of the range. Talc is the only mineral deposits commercially developed in the district. The greatest concentration of talc is south of Idaho Creek. There are also several deposits in an area underlain by marble at Dunegan Mountain (section 14, T8S, R4W). None of these mines appears to be historic (Berg 1979).
BOUNDARIES OF THE DISTRICT
There are no boundary discussions in the mining literature due to the fact that aside from talc, the district is not mentioned at all. Berg (1979) discusses the talc mines in the region in relationship to the Greenhorn Range. Neither Lyden (1948) nor Sahinen (1935) discuss the district.
Figure 1 shows the district as defined by the AMRB (1994) with a smaller area delineated which shows the Greenhorn Range where the talc deposits are located.
HISTORIES OF SELECTED MINES
No historic mines appear in the mining literature.
Abandoned Mine Reclamation Bureau (AMRB)
1994 Mining districts of Montana. Maps 1:100,000 and Map #94-NRIS-129. Compiled and edited by Joel Chavez. Prepared by Montana State Library Natural Resource Information System (NRIS) for Montana Department of State Lands. Helena
Berg, Richard B.
1979 "Talc and Chlorite Deposits in Montana",
MBMG Memoir # 45
Lyden, Charles J.
1948 "The Gold Placers of Montana",
Montana Bureau of Mines and Geology Memoir 26
. Montana School of Mines, Butte.
Sahinen, Uuno M.
1935 "Mining Districts of Montana", Thesis, Montana School of Mines, Butte.