Bear Lake District
Commodities: lead, copper
The principal prospects for lead and copper in the Bear River Range lie within the area of the Bear Lake district, as indicated approximately on Plate 1, but it is reported that prospect pits are scattered all the way from Swan Lake, Idaho, to the vicinity of Soda Springs. A branch of the Union Pacific Railroad is nearby and roads reach most prospects. The lodes have long been known and several shipments of ore, chiefly lead, have been made, but most of the mines have long been abandoned and none has ever received much development. One mine, the Sunset, produced and stored a small tonnage of lead ore in 1932. Mansfield regards the deposits of both lead and copper as of small promise.
The area containing the prospects is underlain by a thick sequence of Paleozoic and Mesozoic strata without known intrusive rocks. Most of the lead deposits are along the contact between the Blacksmith (?) and Ute (?) limestones of Cambrian age. The ore is in irregular replacements, consisting of galena and its oxidation products in a gangue of calcite and dolomite.
The copper prospects lie along a belt about a mile west of that containing the lead deposits mainly along the line of contact between the Blacksmith limestone (?) and the Bloomington formation (?) of Cambrian age. The ore is mainly malachite and azurite in quartz veins and locally tennantite and tetrahedrite in brecciated quartz and jasper.
Montpelier District
Commodity: copper
In an unorganized area east of Montpelier on the Union Pacific Railroad, here called for convenience the Montpelier district, a number of prospects for copper have been opened in Triassic. red beds. A few small shipments have been made, but little work has been done since 1914 and the prospects appear to be of doubtful value.
Near the surface, copper carbonates line joints in sandstone and shale. At depths of 100 feet or more, chalcocite and covellite have been found replacing the woody matter of fossil plant fragments. Deposition is irregular, sporadic, and shows little relation either to stratigraphic horizons or to zones of shearing and fracture. Much of the material appears to be merely copper-stained rock, although some ore containing over 2 per cent copper is present in small masses.
Nounan District
Commodity: copper
Near Nounan, which is located close to the Union Pacific Railroad, copper carbonates and brochantite occur in little developed quartz-filled fissures cutting limestone.
