Guide to the Chrome Mountain Area

Route

Start point

south flank of Chrome Mountain along Picket Pin-Iron Mountain Road

End point

east flank of Chrome Mountain along Picket Pin-Iron Mountain Road

Roads

U.S. Forest Service Road 140 (Picket Pin-Iron Mountain Road)

Total distance

~ 1 km

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Geology

Summary

The Chrome Mountain area lies at nearly 10,000-feet elevation in the west-central part of the Stillwater Complex between the main part of the Boulder River and the headwaters of the East Boulder River. At Chrome Mountain, the olivine +/- bronzite +/- chromite cumulates of the Ultramafic Series are relatively well exposed and stratigraphically broadly resemble those at Mountain View. In addition, a distinctive rock type occurs: a fine-grained dunite which appears to have formed as a replacement of the ultramafic cumulates.

Key Lithologic Features

• various rocks of the Peridotite and Bronzitite zones, Ultramafic Series, including: cumulate ultramafic rocks, chromite seams, and discordant (secondary) dunite</li.

Structures

• Chrome Mountain fault

Landforms

Other Features

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Reference

Raedeke, L.D., and McCallum, I.S., 1985, Guide to the Chrome Mountain area, in Czamanske, G.K., and Zientek, M.L., eds., The Stillwater Complex, Montana: Geology and Guide : Montana Bureau of Mines and Geology Special Publication 92, p. 277-285.

Availability

Order from the Montana Bureau of Mines and Geology. Search for this publication's record at the MBMG for ordering information.