Il8 NEW YORK STATE MUSEUM 



cally related to the former g^roup, but that in this case a more 

 complete alteration has been effected, leaving- little trace of the 

 original limestone walls. The occurrence has some analogy to the 

 magnetites in the western Adirondack region, notably the Fine and 

 Clifton ore bodies, which have been described by the writer^ as a 

 separate type from the magnetites of the eastern and northern 

 Adirondack's. Professor Sjogren has called attention to the Tilly 

 Foster mine of Putnam county as an illustration of the skarn magne- 

 tites, finding a complete agreement in the mineral association with 

 the Nordmarken occurrence in Wermland. The Cranberry deposits 

 of North Carolina, described by Keith, are also placed by him in 

 the same class. 



The quartz-banded specular hematites at Norberg, also seen by 

 the writer in their typical development at Striberg, are remotely, 

 if at all, comparable as to physical features with any deposits in this 

 State. They consist of finely-divided hematite, subordinate magne- 

 tite, and quartz, with a lamellar and oftentimes banded structure 

 due to the alternate arrangement of ore and gangue minerals. This 

 structure may have all the regularity of bedding and has been fre- 

 quently cited in support of a sedimentary derivation of the ores. 

 The wall rock is leptite, with more or less mica in addition to the 

 usual quartz-feldspar aggregate which characterizes that rock, 



xA.t Langban we found iron and manganese ores forming lenses 

 and shoots in dolomite surrounded by granitic gneiss, leptite and 

 diorite. The iron and manganese are not intermixed, as in the 

 similar occurrence at Norberg, but are distributed in separate though 

 often contiguous bodies. The shoot shape is most characteristic. 

 A series of altered trap dikes (called skols, a name applied also to 

 zones of shearing or jointing accompanied by decomposition) seems 

 to be related to the ore deposition, a very interesting feature to 

 which Mr H. V. Tiberg, the manager of the mines, directed our 

 attention. On the upper side of horizontal dikes the shoot may 

 flatten out into a sheet to diminish or disappear below them, suggest- 

 ing that the mineralization has been due to underground circulations 

 after the intrusions took place. 



This brief survey of a few of the central Sweden mines will 

 serve to show the complexity of geological and mineral features 

 which characterize the ore occurrences in that district. As a whole 

 the deposits are fairly distinct from those found in the Pre- 



1 Geology of the y\clirondack Magnetic Iron Ores. N. Y. State Mus. 

 Bui. 119, 1908, p. 37-42. 



