THE IRON SERIES (IN PART). 91 



2.01.35. In their geological relations the ores are of the greatest 

 interest, as they occur on the western limit of the metamorphic belt, 

 which forms the basis of the Taconic controversy, yet in strata 

 which have been identified by fossils. Beds of limonite hitherto 

 regarded as Siluro-Cambrian occur to the east ; and should further 

 study, on the lines developed chiefly by J. D. Dana, W. B. Dwight, 

 and C. D. Walcott, clear up their stratigraphical relations, the 

 work done in developing the structure of the siderite basins, as 

 pointed out by Kimball, may be of great aid in explaining them. 

 Very similar bodies of siderite occur with these limonites. (Ex- 

 ample 2a.) The Burden ores are relatively high in magnesia, and 

 this leads Kimball to suggest their original deposition from the 

 off-shore drainage of the basic rocks of the Archaean highlands. 

 Further, it may be added that the ores in their lenticular 

 shape are highly suggestive of a possible origin for magnetite de- 

 posits, and they are again referred to under " Magnetite." Other 

 deposits of siderite in the shales of the Marcellus stage are known 

 and were formerly worked at Wawarsing, Ulster County, across 

 the Hudson River. 1 



2.01.36. Example 5. Roxbury, Conn. A fissure vein in gneiss, 

 six to eight feet wide, of crystalline siderite, with which are as- 

 sociated quartz and a variety of metallic sulphides, galena, chal- 

 copyrite, zincblende, etc. Although productive in former years, it 

 is no longer worked, and is of scientific more than economic inter- 

 est, being a unique deposit. It has furnished many fine cabinet 

 specimens. 2 



1 J. P. Kimball, " Siderite Basins of the Hudson River Epoch," Amer. 

 Jour. Sci., III., xl. 155. I. Olmstead, "Distribution of Phosphorus in the 

 Hudson River Carbonate," M. E., 1889. R. W. Raymond, "The Spathic 

 Ores of the Hudson River," M. E., IV. 309. J. C. Smock, Bulletin of New 

 York State Museum on Iron Ores, p. 62. 



2 J. P. Lesley, Iron Manufacturers' 1 Guide, p. 649. C. U. Shepherd, 

 " Report on the Geology of Connecticut," 1837, p. 30, Amer. Jour. Sci., L, 

 xix. 311. 



