I06 NEW YORK STATE MUSEUM 



features exhibited in individual instances. They are not veins in 

 a genetic sense, although they often show a tabular development 

 with sharp boundaries against the country rocks, in common with 

 secondary vein deposits. Some of the occurrences extend for several 

 miles along the strike, although in such cases the magnetite is dis- 

 tributed among separate bands or lenses arranged in series, end to 

 end or overlapping to some extent, the whole constituting an ore 

 zone. The Lyon mountain, Palmer hill, Arnold hill and Cook hill 

 deposits in Clinton county, the Barton hill-Fisher hill series at 

 Mineville and the Benson Mines series in St Lawrence county 

 illustrate this method of occurrence. Not infrequently the deposits 

 assume very intricate forms, like the body opened by the 21- 

 Bonanza-Joker Mines at Mineville, which are hardly explainable 

 as the effects of regional compression and folding upon original 

 lenses or tabular deposits. Rather they point to inherent irregu- 

 larities assumed in the process of magmatic segregation. 



The ores range from rich magnetites, with 60 per cent or more of 

 iron, through all gradations down to very lean mixtures of magnetite 

 and gangue minerals — in fact the lower limit is reached in the 

 ordinary country rocks of S3^enite and granite which contain a few 

 per cents of free iron oxides in the form of magnetite. The richer 

 ores are likely to contain moderate to high amounts of apatite, as 

 much as 10 per cent in Mineville Old Bed product, so that they are 

 more emplo5^ed for foundry and basic pig. The leaner ores which 

 require beneficiation by crushing and concentration are relatively 

 lower in phosphorus content and many come within the class of 

 Bessemer and low-phosphorus ores. The Chateaugay mines afford 

 an exceptionally desirable product, comparable to the best Swedish 

 ores in regard to phosphorus and sulphur. 



The titaniferous ores, mixtures of magnetite and ihnenite in 

 varjang proportions, .are associated with the low-silica or basic 

 igneous rocks and represent segregations of the heavy constituents 

 of the magmas while in a fused state. The largest bodies occur in 

 the great anorthosite bathylith that constitutes the central and 

 eastern Adirondacks, the region of greatest surface relief. They 

 are also met with to some extent in the smaller bosses and dikes 

 of gabbro that border this area. A singular example, occupying an 

 intermediate position between these ores and the normal magnetites, 

 is represented by a deposit near Port Leyden, Lewis county, within 

 syenite gneiss and with a content of about 10 per cent titanic oxide. 

 The average for the other deposits is from 15 to 20 per cent titanic 

 oxide. 



