22 



same gangue, which either entirely cuts it off on one side, or 

 being of limited length, soon permits the reunion of the divided 

 portions. 



Not unfrequently this gangue comprises the chief width of the 

 vein, and the ore included in it lies in detached elongated bodies 

 of lenticular form, having their longer axes always in the direc- 

 tion of the course of the vein. These insulated masses of the 

 ore, denominated ^w^s or pools by the miners, are sometimes 

 more than a hundred feet in length, their thickness varying in 

 certain large veins from five to forty feet. 



Another feature, deranging occasionally the uniformity of 

 these veins, presents itself, \^ hen detached portions or splinters, as 

 we may regard them, from the adjoining strata constituting the 

 walls, are found lodged in the substance of the lode. These and 

 other smaller wedge-shaped masses, interrupting or dividing the 

 vein, are commonly entitled horses by the miners. 



In addition to these irregularities in the distribution of the ore, 

 we sometimes find the entire vein cut through by faults crossing 

 it, commonly almost at right angles, and totally interrupting its 

 continuity. 



The several circumstances here spoken of in the structure of 

 these metalliferous veins, seem strongly to imply that they are real 

 veins of injection, and not true beds, contemporaneous with the 

 adjoining gneiss, as some have supposed. A common thickness 

 of the metalliferous veins under description is from six to twelve 

 feet; in their inclination or pitch they are quite various, some 

 dipping, with the strata that enclose them, at as low an angle 

 as 50°, while many are nearly verticak In the shallower exca- 

 vations the workings are open to the sky, and the deepest 

 shaft yet sunk, that of the Mount Pleasant Mine, near Dover, in 

 Morris county, is only about two hundred and twelve feet below 

 the surface. 



Nature of the Ore. — The ore belongs to the species denominated 

 bv mineralogists oxidulated iron or magnetic iron ore, and is of 

 two varieties — compact and granular. In its purest form, this 

 mineral consists of two atomic proportions of the peroxide of 

 iron, and one of the protoxide, which is equivalent to nearly 

 72 per cent, of the former, and a little more than 28 per cent, of 

 the latter — yielding about 72 per cent, of metallic iron. In the 



