236 GEOLOGY OF THE SECOND DISTRICT. 



they have upon llic theory of the origin of tlie primary ore of iron, than from their importance 

 in an economical point of view. The ferruginous dyke, or iron stone, is very probably an 

 injected mass ; or at least iriost individuals who have a knowledge of the phenomena of dykes 

 and veins, would not hesitalc to call this ore an instance of injected matter. 



Some of the examples of the peroxide, however, have in their origin only a slight resem- 

 blance to dykes ; those deep cylindrical masses, perforating a rock perpendicularly, are with- 

 out doubt contemporaneous in tiicir origin with the rock in which they are found, having been 

 caught in the midst of the rock while in a soft state. The few localities of this kind of ore 

 in Essex, resemble very much those in the same state of oxidation in St. Lawrence county, 

 some of which I have noticed in my general account of the rocks of that district. 



Vein at Crag Harbor. 



1 shall now describe several veins, whose qualities and capabilities have been established 

 by experience. 



The first is the Crag Harbor ore, situated directly upon the lake, in a cliflf which almost 

 overhangs it, and about fifty feet above the water. It is not far from half a mile below Port 

 Henry ; hence, so far as location is concerned, it is favorable, being the most accessible of 

 all the veins in this mineral district. This vein is in hornblende, with which the ore is 

 somewhat mixed. It is twelve feet wide, and dips southwest, or rather west, at an angle of 

 thirty-five degrees. The rock at this place dips west thirty degrees.* 



This ore is black, rather compact, or subcrystallinc ; it is, however, extremely tough, and 

 difficult to reduce to a slate of sufficient fineness for the forge. Burning or roasting suffi- 

 ciently will do much towards overcoming this difficulty. It is strongly magnetic, though its 

 polarity is feeble. Iron pyrites occurs in thin seams, but it does not appear to be dissemi- 

 nated through the mass. Black mica occurs also in the vicinity. The specific gravity of this 

 ore is 4 '729 ; and it yields, on analysis. 



Protoxide of iron, 24 " 50 



Peroxide of iron, 64 • 80 



Silica, alumina, etc 8 '70 



100-00 

 Proportion of metallic iron, 65' 23 in 100 of ore.f 



This vein ajipears for half a mile along the lake ; and though it occurs nearer the furnace 



than some others, yet it has not proved so profitable as those more distant. The iron from 



this ore is hard and brittle, and hence for many purposes it cannot be employed ; yet it seems 



desirable that farther experiments should be made with it, for the purpose of ascertaining 



some mode by which the quality of the iron may be improved. 



— • • ■ ■ — ■ — ■ : . ^— 



• The (lip of the vein is often greater than that of the strata enclosing it, f Dr. L. C. Beck, Report of 1837, p. 25. 



