Gabbroid Rocks of Minnesota . — Wine he II. 277 
Pseudomesolite is slowly but completely attacked by the 
acids leaving a residue of gelatinous silica. The microchem- 
ical reactions of Boricky and Behrens show an abundance of 
alumina, considerable calcium, and less sodium. 
Inclusions are not common; particles of hematite occur in 
the form of particles and microscopic lamellae. On alteration, 
pseudomesolite becomes translucent, instead of transparent, 
in thin section, and becomes filled with cloudy masses re- 
sembling those of altering acid feldspars. These cloudy 
masses seem to have lost their crystalline character, at least in 
large part. 
' The material for chemical analysis was carefully freed of 
all the other minerals of the rock. A large spherulitic mass of 
nearly pure zeolitic mineral was repeatedly tested and the 
elongation of the fibers was found over twenty times to be 
uniformly positive; therefore no mesolite was present in the 
mass. Only the white and pink bands were utilized, so that 
the iron found was undoubtedly foreign to the zeolite. In the 
first column below are given the results obtained; the others 
are the results of various calculations except the sixth, which 
gives the composition of gonnardite. 
I 
II 
III 
IV 
V 
VI 
VII 
VIII 
SiOg 
45-25 
45-89 
46.75 
46.40 
41.7 
46.35 
45-99 
52.99 
TiOs 
none 
Al,03 
25.69 
26.06 
29.49 
26.30 
28.4 
26.27 
26.11 
30.38 
FCgOg 
1.40 
MgO 
trace 
CaO 
9-75 
9.89 
9.70 
9.50 
9.7 
10.00 
9.91 
II. 41 
NasO 
4.24 
4-30 
5-37 
5-44 
6.3 
4.89 
4-79 
4-97 
K2O 
•47 
.48 
-55 
H3O 
12.99 
13-17 
99-79 
11.69 
100.00 
12.36 
r 00.00 
13-9 
100.00 
12.49 
13.20 
100.00 
99-79 
100.00 
IOO.( 
Sp. Gr 
. 2.219 
2.2 
to 2.4 
2.246 
to 2.2 
;6 
I. Pseudomesolite from the plagioclasyte of Carlton peak, Minn. 
Analysis by the method of Deville; water determined by the loss on 
ignition. 
II. Analysis I, calculated after deduction of the iron. 
III. Theoretical composition of CaNaAl3Si30io+2.5H„0. 
