Gabbroid Rocks of Minnesota. — WincJicll. 2 1 9 
In general the order of crystallization is that given above, 
but it is probable that the apatite and magnetite crystallized 
out of the molten mass at about the same time; they are in 
such small quantity that in crystallizing they never mutually 
interfered, and consequently the earlier one cannot be deter- 
mined. Magnetite is occasionally seen enclosed by apatite but 
in such cases the iron ore is apparently always secondary and 
due to percolating waters. Both are, however, very distinctly 
earlier than the great masses of the augite and labradorite. 
The relation between the magnetite and augite is rarely evi- 
dent as both are in small quantity, but in one case an augite 
crystal molds itself about the corner of a well-formed magne- 
tite crystal, and is itself surrounded by xenomorphic feldspar. 
In another case, which will be described in detail later, it 
is clear that the periods of crystallization of the magnetite and 
augite were partially contemporaneous. The relation between 
the augite and labradorite is somewhat variable, but in general 
the pyroxene is of earlier growth; while the larger part crys- 
tallized before the feldspar, there remained a very noticeable 
amount which did not solidify until the crystallization of the 
feldspar was already well advanced. This part is seen filling in 
the spaces between the labradorite anhedra. But it must be 
understood that these spaces are comparatively' rare, and that 
in general the feldspar anhedra are limited only by other crys- 
tallizations of the same mineral. Thus the feldspar considered 
alone forms a mass of very coarse granitic texture. A peculiar 
and exceptional development of augite (shown in plate X, Fig. 
I ,-) occurs in a section irom Carlton peak. It is unfortunately 
in a highly altered area, so that the augite is nearly separated 
from the feldspar, and their relations are uncertain. How- 
ever, it is very probable that the augite is wholly younger than 
the feldspar. A rather large mass of augite of irregular shape 
showing a twinning band with composition plane /!^(ioo), is 
surrounded by several small well developed crystals of augite 
oriented exactly with the contiguous parts of the large mass. 
Thus the crystals bordering on the twinning band are oriented 
with it, while the others are oriented with the principal mass. 
The central mass is surrounded nearly everywhere by a nar- 
row^ band of magnetite which crystallized before the formation 
of the satellites. On the other hand the satellites themselves 
