1 50 The American Geologist. Marcii, 1898 
forms and dense masses in badly decayed portions of the rock 
from certain localities. In some instances this secondary 
maj^^netite constitutes almost a perfect outline of an original 
mineral constituent, and usually accumulates along the mar- 
gins or in the crevices of such decaying minerals. 
Hematite. Ferric oxide is abundant asa staining substance 
in the sandstones and conglomerates. In many places the 
veining produced by the accumulation of this oxide in the 
sandstones produces branching figures of surprising com- 
plexity. In other places accumulations are more abundant 
and exhibit all the characters of hematite ore. Hematite is 
also formed as a fissure filling in the diabase. And the quartz 
of these rocks is highly colored by especially beautiful den- 
dritic crystallizations. The rusty brown color noticeable on 
decaying surfaces of the mottled diabase is ferric oxide. The 
calcareous shales are so highly charged with it as to present a 
brown red color on a fresh fracture. But in spite of its 
abundance and wide distribution, there' is no considerable 
segregation at any single point. 
Caleite. Within cavities in the conglomerate at St. Croix- 
Falls there are developed numerous well-formed caleite crys- 
tals. They are chiefly of the nail head variety, although other 
forms also occur. A similar crystallization of calcium carbon- 
ate occurs in the conglomerate at Taylor's Falls, but the crys- 
tals are not so well-formed nor so abundant as at the other 
locality. Crystalline caleite occurs sparingly in the diabase. 
Travertine. This variety is deposited in ver)' compact 
and well banded masses in the larger cavities and caverns of 
the Dresbach formation along the river blufifs. 
Dolomite. Small crystals of dolomite associated with 
caleite are abundant in the conglomerate at Taylor's Falls. 
Certain compact portions of the exposure exhibit a crystalline 
phase in which the chief constituent is dcolomitic in composi- 
tion. 
Malaehite. Malachite is seen in many places near a contact 
of the sandstone and diabase as a green, earthy coating upon 
([uartz grains or in cavities among the boulders of conglom- 
eratic phases of the rock. It is especially noticeable at the 
Taylor's Falls conglomerate exposure. Oxide of iron con- 
taining copper and coated with malachite was secured from 
Sec. I, T. 33 N., R. 19 W., from the sandstone. 
