wolff.] ZINC AND MANGANESE OF FRANKLIN FURNACE, N. J. 215 
so with the relative proportions of the other three. The size and shape 
of the" minerals also vary greatly. A common form is the "shot" 
ore in which irregular rounded franklinite, willemite, and calcite 
grains, with or without zincite, occur together without marked band- 
ing; at other times the ore is finely banded or foliated, and these 
minerals are then seen to be in small flattened lenses or elongated 
pod- like masses parallel to the foliation; or such forms may be due 
to an aggregate of several grains. At other times large round masses 
of zincite, 1 or 2 inches in diameter, are scattered through coarse cal- 
cite like a pudding stone, or franklinite occurs similarly in rough 
octahedral crystals. These four minerals have evidently been formed 
contemporaneously, for each is found inclosed in the others and 
neither in general has any distinct external crystal planes, although 
the franklinite has a tendency to occur in rounded octahedral grains. 
These structures in general simulate so closely that of the associated 
gneisses that they must be classed together. 
GEOLOGIC OCCURRENCE. 
At Mine Hill the zinc deposit is much like a bedded deposit, and 
forms a band which outcrops on the surface as far north as the 
extreme point of the gneiss band lying west of the white limestone, 
and runs southwest for about 2,700 feet (Trotter and other mines), 
when it makes a sharp curve and runs northeast about 600 feet (Buck- 
wheat mine) as far as the trap dike, where it disapijears from the sur- 
face, and has been worked underground in a northeast direction for 
about 600 feet on a pitch of 27° to 32°. By diamond-drill exploration 
the further underground continuation of this deposit to the northeast 
was found at depths of 1,000 feet more or less from the surface, a 
shaft was sunk, and extensive mining operations are carried on 
(Parker shaft workings). 
The west limb of the deposit is known as the " front vein" and the 
east limb as the "back vein," while the connecting point is known as 
the "South chamber." 
Along the west outcrop the ore body has a width toward the north 
end of 15 to 25 feet. It is separated from the gneiss by 30 feet of 
limestone and dips east at from 55° to 60°. The distance from the 
gneiss is remarkably constant, for the same 30 feet of limestone 
between the foot wall of the ore deposit and the gneiss is found at the 
surface, and 900 feet vertical^ below and 1,200 feet along the dip. 
The foliations of ore and limestone are conformable. 
At the Trotter mine the ore body is divided by a large mass of 
granite, which was also found underground for a long distance. South 
of this mine the deposit widens considerably. It has been followed 
down about 500 feet along the dip from the outcrop of the west vein, 
widening and narrowing and with some variation in the angle of dip. 
