THE' 



fom-Ofe Districts of New Yoi^. 



I.-THE HIGHLANDS OF THE HUDSON - MAGNETIC 



IRON ORES. 



Magnetite is one of the common minerals in the crystalline rock 

 region of the Highlands. It occurs as an accessory constituent in the 

 granitic and gneissic strata ; and by itself, forms beds of considerable 

 extent and thickness. Accordingly as it is more or less' free from 

 foreign minerals it is rich or lean, varying from the pure magnetic 

 iron ore to rock with traces only of iron in its mineral ogical com- 

 position. The beds of ore show lamination and planes of bedding 

 and are faulted, folded and contorted as the enclosing strata of rock; 

 and have the same general strike and dip in common with the latter. 

 They are generally of irregular form, in places widening into thick 

 deposits or lenticular-shaped masses, in others, contracted in thin 

 sheets, which are not mined profitably. The ore is found in some 

 cases to separate into thin layers ; and masses of rock (" horses ") are 

 met with, entirely surrounded by the ore. The phases of variation 

 are as many almost as there are mines, where they can be studied. 

 In the larger and older mines the ore has been followed for thousands 

 of feet in the line of strike or on the course of the ore, and for hundreds 

 of feet in depth (on the line of dip) without reaching its limits. 

 Owing to the unprofitable nature of working so thin ore beds, they 

 are often not followed to the end, and the real extent of few of these 

 ore deposits is known. In general, it may be stated that in this 

 region the ore beds stand nearly on edge and have a north-east and 

 south-west strike and a descent or dip at a steep angle to the south-east. 

 In consequence of their highly inclined position and their irregular 

 shape, these ore bodies are called "veins"; less frequently, "chim- 

 neys" and "shoots" of ore. 



