148 



NEW YORK STATE MUSEUM 



ical examples. No. 1 relates to the gabbro at the Split Rock mine; 

 No. 2 to gabbro at Lincoln pond; and No. 3 to anorthosite from 

 Mt Marcy. 



1 2 3 



Si0 2 47.88 



Ti0 2 1 . 20 



Cr 2 3 tr. 



A1 2 3 18.90 



Fe A 1 -39 



FeO 10. 45 



NiO.CoO 02 



MnO .16 



CaO 8.36 



SrO tr. 



Bad tr. 



MgO 7.10 



K 2 81 



Na 2 2.75 



Li 2 tr. 



H 2 61 



PA 20 



V 2 5 tr. 



C0 2 12 



S. . . . v .07 



44 



77 



5 



26 



12 



46 



4 



63 



12 



99 





tr. 





17 



10 



20 



5 



34 





95 



2 



47 





60 





28 





37 





26 



54-47 



26.45 



i-3o 

 .67 



10.80 



.69 

 .92 



4-37 

 •53 



100.02 100.75 100.20 



The Port Leyden ore body on the west side of the Adirondacks 

 seems to be an anomaly among the titaniferous occurrences. The 

 wall rock is not a basic variety belonging to the gabbro-anorthosite 

 family, but a quartz gneiss with potash feldspars and a small 

 quantity of ferromagnesian minerals. Yet it is not unlikely 

 that the deposits may represent only an aberrant type of the 

 ordinary occurrences. If the country rock is igneous, as is believed, 

 it probably belongs to the general series of intrusives that origi- 

 nated from a common parent mass. The ultimate source of the 

 iron minerals may thus have been the same as those of the gabbros. 



In the relations they bear to the inclosing rocks, the ores are 

 sharply differentiated from those of the nontitaniferous class 

 which occur in the sedimentary gneisses and schists. They are 

 themselves only a phase or development of the igneous magma 

 from which the walls have been derived — that is they are rocks 



