CHARACTER OF THE METALLIFEROUS VEINS. 
145 
twelve inches thick. The dykes are com¬ 
posed of a greenish, foliated crystalline 
feldspar. The disappearance of a net work 
of nonmetallic veins, is by no means an 
uncommon circumstance in mining in North¬ 
ern New York, and hence there is encourage¬ 
ment in mining of this description, that the 
dead work will diminish as it progresses. 
The gangne of this ore is phosphate of lime, 
in small reddish particles, imbedded in the 
grains of the oxide. They are usually of 
the size of a kernel of wheat. When the 
phosphate is separated, the iron made from 
this ore is good, but if manufactured with 
the phosphate it is brittle. This mineral 
constitutes about one-fifth of the mass—but 
in parts of the vein it is equal to one-half of 
the mass of ore. The phosphate is now sepa¬ 
rated by magnetic separators, is ground and 
prepared for use in agriculture. 
Adventurers in mining are often startled 
on finding the vein diminishing in width. 
In iron mining, however, those fears are 
Fig. 33. 
h Constricted Part of the Vein, c Gneiss, 
19 
