228 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



Bailey's Pond, and the Lombardy in Italian Gulch north of Kellogg. 

 They probably occur as characteristic minerals in all of the veins of 

 this group. 



Ankerite also occurs in many of the veins in the Prichard formation 

 in the Pine Creek Basin, in many of which it is associated with galena 

 and sphalerite as well as iron sulphides and chalcopyrite. It has been 

 seen in ore on the dumps of the Bobbie Anderson, Northern Light 

 Amy-Matchless, and Shetland claims. A specimen from the Sher- 

 man mine contains crystals of ankerite up to 3 cm. in diameter, of 

 a grayish color, and showing fine twinning striations. These are 

 surrounded by scaly chlorite and contain cleavage cracks coated 

 with films of pyrrhotite. The ankerite turns brown where weathered. 

 Specimens from the Casey prospect in Bear Gulch, tributary to Pine 

 Creek, contain granular gray ankerite in ore consisting of galena 

 and sphalerite with pyrite in quartz. Small brown-weathering gray 

 grains are associated, in quartz, with galena and chalcopyrite in 

 ore from the Bobbie Anderson mine and similar ankerite occurs with 

 galena and sphalerite in quartz in ore from the Spokane group. 



While, in Shoshone County, the occurrence of siderite is somewhat 

 local and is characteristic of the silver-lead ore bodies, and their 

 neighborhood, the distribution of ankerite-bearing veins is more 

 general, especially to the south and east. A large vein having the 

 typical chalcopyrite-ankerite filling is mined for copper at the Amador 

 mine on Cedar Creek south of Iron Mountain, Mont., 40 miles east 

 of the Mullan area, and numerous similar veins occur in the inter- 

 vening territory, while such veins are reported from numerous 

 localities in the St. Joe and Clearwater Basins. 



As regards the disseminated carbonates in the sedimentary rocks 

 of the Coeur d'Alene region, no definite evidence has been accumu- 

 lated, mainly because the existence of carbonate in them is only 

 manifest after it has oxidized and no field work has been possible 

 since the problem developed. Judging from the nature, color, 

 and appearance of the oxidation products it seems probable, as 

 concluded by Ransome and Calkins, that the abundant carbonate 

 in the quartzites of the productive area of the mining district is 

 siderite. The disseminated carbonate present in wide distribution 

 in the Belt formations, the existence of which has been used by 

 Hershey as evidence opposing certain conclusions of Ransome 

 regarding ore genesis, is very probably ankerite or only moderately 

 ferruginous dolomite. 



