Moyie Yaak District
Commodities: gold, lead, silver, molybdenum, tungsten
This large, but little developed, district includes most of Boundary County east of the Kootenai River. Its southeastern part is sometimes termed the Katka or Katka-Leonia district. Other parts of it have received local names, such as the Queen Mountain and Brush Lake districts. Branches of the Great Northern Railroad traverse the river valleys, but many of the prospects are accessible only by trails. Numerous lode and some places prospects are intermittently operated, but the production as yet has been small. The principal metals sought are gold, lead, silver, molybdenum, and tungsten.
The district is underlain by Belt strata with intercalated large and closely spaced basic sills (pre-Cambrian), both cut by great masses of Mesozoic granitic rock.
The lead-silver veins appear to be similar to those in the northern part of the Clark Fork district, but have been little developed. Gold-quartz veins are known in shear zones in quartzite of the Belt series and also in basic sills. The gold is free and appears to be associated with pyrite and pyrrhotite. It has been suggested that the veins in the sills derive their gold from the sills themselves, but the evidence is inconclusive. Molybdenite has been found in veins of quartz and mica, resembling pegmatite. The tungsten prospects are on quartz veins containing scheelite and specks of galena, pyrite, and pyrrhotite. Garnet, actinolite, enstatite, and hypersthene are present in the rock nearby.
Porthill District
Commodities: lead, silver
This district contains the Idaho-Continental lead-silver mine, which was productive from 1915 to 1928, and a number of prospects. The mine, which is 26 miles by road from Porthill on the Great Northern Railroad, is in quartzite, probably Belt, with large granitic masses nearby. The veins are replacement deposits in shear zones containing argentiferous galena, pyrite, siderite, and a little quartz Molybdenum deposits are also reported.
