Birch Creek District
Commodities: copper, lead
As mapped on Plate 1, this district, which is about 50 miles by road from points on the Butte branch of the Union Pacific Railroad, is the southern extension of the Nicholia district, sometimes included in it, Campbell extends the name to include the east flank of the Lemhi Range, bordering the Hamilton and Dome districts, but there appear to be few prospects and no mines of consequence in that area.
Parts of the Birch Creek district are sometimes termed the Skull Canyon and Buck Creek districts. The Heart Mountain district, to which one property is credited in the 1932 report of the State Inspector of Mines is probably also part of the Birch Creek district,
Ore deposits were first discovered here in 1885, The total production is somewhat over $150,000, of which nearly half is from the Weimer copper mine, and much of the rest from the Scott lead mine, both of which lodes were among the first discovered in the district. Operations have continued intermittently up to the present time, but recent production has been small.
The district is underlain by Paleozoic sedimentary rocks with basalt flows and gravel in the valley of Birch Creek, Except for a few Pliocene (?) dikes, intrusive rocks appear to be absent.
Most or all of the lodes are replacements in limestone and quartzite, in part controlled by shearing or bedding planes. Many are pipe-like and irregular. The copper deposits contain chalcopyrite, chalcocite, and oxidized copper minerals in a gangue of altered gouge-like rock with calcite, barite, and jasper. In the lead deposits, galena and its oxidation products are plentiful, and pyrite, sphalerite, tetrahedrite, and covellite also occur.
Continental Divide Coal District
Commodity: coal
There are several prospects for coal, as yet undeveloped, along the Continental Divide in northeastern Clark County. Those in T. 14, N., R. 38, 39, E., not far from points on the Butte branch of the Union Pacific Railroad, expose coal, some of which is of possible future commercial value, but no coal was found by Mansfield in the prospects in T. 14 N., R. 40 E.
The coal-bearing rocks are Cretaceous sandstone, shale, and clay, locally exposed by erosion of the overlying Tertiary volcanic and sedimentary strata. The exposed coal beds vary from a few inches to nearly 3 feet in thickness, and analyses indicate that they are of sub-bituminous grade or somewhat better.
