ADIRONDACK MAGNETIC IRON ORES 6/ 



soda, but the inference has not yet been corroborated by analysis. 

 The augite is, however, a much more characteristic igneous than 

 metamorphic mineral, and militates against original sediments as 

 the sources of the rocks and ores. The lean ores are mixed with the 

 usual minerals of the wall rocks and among these the basic syenite 

 is chief. Hornblende and biotite appear and bring down the per- 

 centage of iron. The Old Bed group is pretty sharply marked off 

 against the acidic " 21 " gneiss, the quart z-microperthite aggre- 

 gate, but scattered grains of magnetite continue out through the 

 latter for many feet. 



Anorthosites. This great group of undoubted eruptive rocks is 

 specially represented in the western and northern portion of the 

 area. Its typical representatives consist almost entirely of labra- 

 dorite which may be very coarsely crystalline, still there are always 

 minor amounts of augite and titaniferous magnetite and often 

 hypersthene associated with the feldspar. The dark silicates some- 

 times become relatively abundant and lead to much variation in 

 the rocks. At least one distinctive eruptive mass is known, charac- 

 terized by relatively large amounts of them and later than the 

 main anorthosites. At the headwaters of the Hudson the anor- 

 thosites contain the large bodies of titaniferous magnetite, else- 

 where described in this bulletin, but they are not known to carry 

 ores anywhere in the vicinity of Port Henry. The known titan- 

 iferous masses of this region are all in the basic gabbros. 



Grenville series. Under this name it has been agreed between 

 Canadian and American geologists to describe the undoubted 

 metamorphosed sediments. They constitute an important belt 

 underneath Port Henry and for 3 miles or more north. They 

 appear also west of Moriah Corners and well over to the foothills 

 of the bounding mountains on the west. The most easily recog- 

 nized of these rocks is a coarsely crystalline white limestone, with 

 graphite and many bunches of included silicates. There is less 

 often a serpentinous variety or ophicalcite and with these are rusty 

 quartz schists, mica schists, hornblende schists and thinly foliated 

 gneisses. While there has been in the past a disposition to class 

 with these the more massive gneisses yet it has been a growing 

 belief as set forth above that the latter really represent the syenitic 

 series of eruptives. The limestones and their included bands of 

 silicates are mashed and folded in many complex and involved 

 curves, some of which are curiously and strikingly suggestive of 

 snakes and other organic forms. The sedimentary metamorphic 

 rocks may possibly contain some ore bodies. The Lee bed of sul- 



