White Limestones of Sussex County, N~. J. — N~ason. 159 
the surface, the principal part oi' the limestone was a dark, 
bluish gray to a dirty white color, all non-effervescing except 
with hot acid. In consideration of this behavior it is, with- 
out doubt, of the same composition as the dolomite in analysis 
No. VII. There were two or three granite dikes encountered 
within this distance of 450 feet and on either side of these 
dikes the limestone was white, sparkling and filled with the 
minerals above named. 
The above analyses seem to be a clear demonstration of the 
fact that the franklinite ore body lies in a magnesian lime- 
stone, in fact a true dolomite, except the instances named, 
when the limestone came in contact with granite dikes; 
second, that the white limestone is generally non-magnesian 
only when in close contact with granite or some other eruptive 
rock. This last conclusion has been stated in advance of 
many facts supporting it. The latter facts have been ob- 
served on the surface at surface contacts alone, but this one 
fact stands out very clearly, that in the shaft and in the drill 
cores the magnesian limestone extends through the whole 
thickness of the formation. When non-magnesian limestone 
occurs, it is in connection with granite, which may or 
may not appear on the surface. There may be some excep- 
tions to this rule, for the writer was not present during the 
sinking of the shaft. The difference in the color of the magne- 
sian and non-magnesian limestone is so great, however, as to 
he noted by the men. Mr. Van Mater has observed this rela- 
tion, that is, between the white chondroditic limestone and 
granite; Furthermore, the writer has observed on the dump 
from the shaft that when granite comes to the surface it is 
accompanied by non-magnesian limestone; at other times only 
the other variety is noted. 
About 1,000 feet south of the southwest opening (see tig. 1, 
a) is what is known as the furnace quarry. This quarry sup- 
plies the blast furnace with flux. It is a very sparkling, white 
limestone, for the most part, ami has a greal deal of chondro- 
dite, tourmaline and other minerals present. There is con- 
siderable tremolite present, but it is in small crystals and is 
not readily observed. Through the center of this quarry runs 
a great dike of allanite granite. Its eruptive nature is clearly 
shown by its numerous adventitious dikes reaching out into 
