FOURTH REPORT OF THE DIRECTOR I907 7 1 



lationships, and with the schists and hmestones of the sedimentary 

 (Grenville) type. Their origin is obscure, a problem that has been 

 fruitful in discussion and theorizing among geologists. It is doubt- 

 ful if any one of the explanations that have been advanced is satis- 

 factory as a general basis for the whole group ; rather it would seem 

 that the varying conditions surrounding the character and associa- 

 tions of the deposits indicate that they have been formed by a com- 

 plexity of processes which may have differed materially in individual 

 cases. 



The titaniferous magnetites are distinguished from those of the 

 preceding group by their higher percentage of titanium, which 

 ranges from about 3 or 4 per cent, as a minimum up to a maximum 

 of 10 or 15 per cent, and by the fact that they are always inclosed 

 by basic igneous rocks of the gabbro family. They have been de- 

 scribed by Prof. J. F. Kemp as basic segregations formed during 

 the cooling and consolidation of the wall rocks, an explanation that 

 is generally regarded as correct. Some of the largest deposits of 

 iron ores in the region belong to this class, those of Lake Sanford 

 being specially extensive. After a long period of inactivity, due 

 to the difficulties encountered in smelting the ores in the blast fur- 

 naces, attention is now being directed to the deposits with a view 

 to their utilization. It has been found that the ores in some cases 

 at least are not simply magnetite carrying titanium uniformly 

 through its mass, but that they consist of a mixture of magnetite 

 and ilmenite, the former having almost no titanium, a condition that 

 is favorable to their commercial treatment. 



The hematite ores are practically limited to the western Adiron- 

 dack region of St Lawrence and Jefferson counties. In this area 

 the Grenville schists and limestones attain wide development, form- 

 ing an interbedded series which has been upturned and sharply 

 folded. Granite intrusions are numerous, but there is a noticeable 

 lack of the basic igneous rocks that occur abundantly in the central 

 and eastern Adirondacks. The ore bodies consist of lenticular, 

 tabular, or irregular masses inclosed within belts of the schist and 

 limestone, or lying along the contact of these rocks as at the Cale- 

 donia mine. Stringers and larger bands of ore often extend out 

 from the main bodies for considerable distances into the fcx^t and 

 hanging walls. The deposits have originated, without much doubt, 

 by a process of replacement. They grade at the ]:»ordcrs into the 

 wall rock and frequently inclusions may be found that show com- 

 plete transition from the rock to the ore. Where tlic walls are 



