METAMORPHIC ROCKS. 
471 
subsisting between some of the parts comprised in this curiously heterogeneous belt of mineral 
matter. The vein in its course to the southwest, undergoes a considerable change in its cha¬ 
racter. About two hundred yards southwest from the place already mentioned, it appears to 
consist almost wholly of garnet rock and jeffersonite, some of the latter occurring in enormous 
crystals, projecting from the face of the rock, but so fissured and readily broken as to render 
it difficult to procure them entire. 
“Further still to the southwest, and nearly opposite the Old Forge, are considerable exca¬ 
vations made in former times for iron ore. The ore was far from pure, abounding in frank- 
linite ; which, by the manganese and zinc contained in it, seriously interfered with the 
conversion of the ore into iron. This ore includes, moreover, a considerable proportion of the 
red oxide of zinc, in some places remarkably pure, being finely lamellated and unassociated 
with any of the franklinite that generally accompanies it, and which interferes effectually with 
its reduction into metallic zinc on a large scale. 
“ Could this pure red oxide be obtained in sufi&cient quantity, it would probably be better 
adapted for smelting into zinc than the mixed ore of the Sterling mine, three miles further to 
the southwest. This somewhat rare ore of zinc, the crystallized red oxide, occupies in com¬ 
pany with the crystallized franklinite, a metalliferous vein, or more probably a line of nearly 
continuous veins, in the crystallized carbonate of lime, extending with occasional interruptions, 
the whole distance from Franklin to a little beyond Sparta, a total length of more than eight 
miles.” 
“ From Franklin we may trace the white crystalline limestone continuous to Sterling, about 
three miles to the southwest. Here we find it lying in contact with a remarkable vein con¬ 
sisting exclusively of franklinite and the red oxide of zinc ; the former in crystalline granules, 
often approaching the octohedral form, invested by a paste of the zinc ore, which frequently 
constitutes more than one-half of the mass. The position of this vein is on the eastern decli¬ 
vity of a hill of considerable elevation, where it occupies the same intermediate relation to the 
gneiss and crystalline limestone which was mentioned of the vein at Franklin. 
“ At Sterling, the metallic vein, where it is visible at the surface, rests with a steep south¬ 
east dip conformably upon the steeply dipping beds of gneiss, rising in the form of a bold 
cliff or wall along the side of the hill. Against this wall of ore, and at the base of the hill, 
repose the beds of the white altered limestone, presenting unequivocal traces of its original 
planes of stratification, showing the sedimentary origin of the rock. It obviously dips at the 
same inclination of from seventy to eighty degrees to the southeast, with the vein and the 
gneiss upon which it lies. 
“ The metalliferous vein is from eight to ten feet in thickness, and consists of no other 
minerals but the franklinite and ore of zinc. From its exposed position on the flank of the 
hill, the ore could be excavated to an almost indefinite extent with a facility unusual in the 
history of mining operations. Zinc of an admirably pure quality has been prepared from this 
ore by Mr. Hitz, under the directions of Mr. Hasler, for the manufacture of the brass for the 
standard weights and measures now making by the latter scientific gentleman for the several 
custom-houses of the United States, by order of Congress. An economical method for the 
