The lead-silver deposits in the Clark Fork district in Bonner County, Idaho, resemble those in the nearby Coeur d'Alene region, but some of the deposits have been substantially enriched by the late addition of hypogene silver and antimony minerals. The unenriched ore consists dominantly of galena, which is accompanied by lesser amounts of siderite, quartz, and sphalerite and by still smaller quantities of pyrite, arsenopyrite, tetrahedrite, bournonite and calcite. Ore that has been enriched by the addition of late hypogene silver and antimony also contains various lead sulphantimonites and sulpharsenites, copper-lead sulphantimonite, silver-lead sulphantimonite, and ruby silver. Minerals formed during the enrichment include boulangerite (5PbS.2Sb 2 S 3 ), geocronite (5PbS.Sb 2 S 3 ), meneghinite (4PbS.-Sb 2 S 3 ), semseyite (9PbS.4Sb 2 S 3 ), jordanite (4PbS.As 2 S 3 ), guitermanite (3PbS.As 2 S 3 ), bournonite (Cu 2 S.2PbS.Sb 2 S 3 ), freieslebenite (2Ag 2 S.-3PbS.2Sb 2 S 3 ) and pyrargyrite (3Ag 2 S.Sb 2 S 3 ). Some of the minerals in this younger group are rare elsewhere, and their local abundance is one of the most interesting features of the Clark Fork mineralization.

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