Gabbroid Rocks of Minnesota. — Wine he II. 267 
rarely, separated from the liquid inclusions, and directly sur- 
rounded by feldspar. They are so small that their nature is 
practically indeterminable; they are completely opaque, black, 
and of irregular outline, usually roughly spherical. They are 
probably magnetite particles. They are certainly not ilmenite, 
since the rock contains no trace of titanium. 
2. Throughout the feldspar. These inclusions are entire- 
ly similar in appearance and occurrence to those found along 
curving planes. They are quite generally distributed, but also 
very sparsely. It is remarkable that these dust-like particles 
are nearly always surrounded by liquid inclusions. It is prob- 
able that the liquid particles in the magma, once in contact 
with a solid particle, adhered strongly to it. 
For purposes of comparison sections were made of labra- 
dorite of various other localities, from samples kindly put at 
the writer's disposal by Prof. A. Lacroix. In sections of the 
well known iridescent labradorite from the island of Paul on 
the coast of Labrador, no augite needles occur, though it was 
from this locality that Schrauf described them. On the other 
hand needles of magnetite* probably titaniferous are abund- 
ant. They correspond exactly in, position and relation to the 
other inclusions of the feldspar to the "augite neediest as 
described by Schrauf. 
The inclusions called microplakites and microphyllites by 
Schrauf, and considered to be wholly, or in part, ilmenite by 
Sheerer, Rosenbusch and Adams, occur in just the position 
assigned them by Schrauf. Minute particles of magnetite 
similar to those described from Carlton peak, also occur, but 
they are very rare. Liquid inclusions are abundant, especially 
along curved planes. 
Sections from the plagioclasyte from Kiew, Russia, an- 
other locality studied by Schrauf, and described as essentially 
similar to the former, show the same titaniferous magnetite 
needles with a total absence of augite needles. The colored 
ilmenite microlitic tablets are abundant here also, but are not 
as characteristically developed. Here the feldspar shows the 
*It will be shown that needles wholly similar sometimes mass 
themselves to form crystals readily determinable in the gabbros oi 
Minnesota and notably in olivine diabase from Birch lake. 
t Augite needles have been found in labradorite from Norway. 
See Lacroix: — Gneiss a pyroxene. Paris 1889. p. 145. 
