Gabbroid Rocks of Minnesota. — WincJicU. 265 
ada, and especially from the Morin district. He decided that 
the "minute black rods" are ilmenite needles. He also found 
red brown scales resembling hematite, but probably also titan- 
ic iron oxide; and fluid inclusions arranged in rows, occasion- 
ally with movable bubles. All these inclusions disappear when 
the labradorite is granulated. 
Bayley * found that the labradorite of the normal Minneso- 
ta gabbros usually contains the "characteristic acicular inclu- 
sions," though they are sometimes absent. He also mentions 
the presence of "dust-like particles scattered everywhere 
throughout the grain." 
Lawson+ studying the plagioclasytes of Minnesota found 
inclusions of three general kinds: 
I. Original mineral inclusions arranged in plates or rods 
parallel to definite crystallographic planes. 
H. Original dust-like inclusions arranged in irregularly 
curving planes without reference to the crystal structure. 
HI. Secondary inclusions of red iron oxide in minute 
specks arranged peripherally to the plagioclase, or along the 
cracks which occasionally traverse it. 
He further concludes that the inclusions of the first class 
are augite needles and granules, which resemble very striking- 
ly the products described by Judd as due to the process of 
schillerization, and yet are demonstrably original inclusions, 
and due to no such process. 
A study of the inclusions in laliradorite from Carlton peak- 
shows that they agree most closely with those described bv 
Lawson, a's might be expected, since he studied the same rock. 
However the "rods or plates" are entirely absent, and no 
inclusions occur arranged parallel to certain crystallographic 
planes. Lawson describes them from another locality (near 
Encampment Island): it is evident they are far from constant 
in Minnesota plagioclasyte. The original inclusions;); which 
occur at Carlton peak may be classed as follows: 
I. Gaseous inclusions are very rare; indeed the few oc- 
*W. S. Bayley: The basic massive rocks of the lake Superior 
region: Jour. Geol. I. 1893. p. 699. 
fA. C. Lawson: The anorthosytes of the Minnesota coast of lake 
Superior: Geo & Nat. Hist. Survey Minn. Bull. No. 8. 1893. p. 8. 
t Secondary inclusions will be discussed under the heading "altera- 
tions" later. 
