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New YORK STATE MUSEtTM 



to be a promising field for exploration southwest of the Caledonia 

 mine, along the contact of the limestone and schist which is mainly 

 hidden by a thin cover of sandstone and has not been actually 

 tested in the immediate neighborhood of the Caledonia mine itself. 

 It is along the contact that the iron-bearing solutions would find 

 the easiest channels for their circulation and the limestone being 

 readily soluble would seem to offer the most available ground for 

 the accumulation of considerable bodies of hematite. 



CaledoTiia mine. This has been one of the main producers in the 

 district and was last worked in 1907 by the Rossie Iron Ore Co. 

 Its output exceeded 500,000 tons. The ore is soft hematite with 

 50 per cent or more of iron, and has a relatively high proportion of 

 lime which is beneficial to its smelting qualities. Actual analyses 

 of ore shipments show 52 to 58 per cent iron, 7 to 8 per cent lime, 

 and . 5 per cent phosphoins. I'he deposit lies near the contact of 

 the Grenville pyritic gneisses and cr^^stalline limestone, and the ore 

 is encountered in both. It is capped in part by Potsdam which 

 rests on ail uneven erosional surface of the crystallines. The gneiss 

 in this place is a quartz schistose phase, carrying graphite and 

 pyrite, more or less altered secondarily to chlorite and serpentinous 

 products, as an accompaniment likely of the ore-forming process. 

 The foot wall which is followed in the main shaft consists of lime- 

 stone, while the schist is seen on the surface to the east and also is 

 encountered underground in the hanging and as horses within the 

 ore. The limestone along the contact with the deposit is uneven 

 and contains pockets and irregular cavities filled with hematite. 

 The hematite not infrequently bears marks of replacement in its 

 simiulation of the banding and structural character of the gneiss. 



Occurrence of hematite in the Caledonia mine, St Lawrence county 



