PETROGRAPHY. 
Chemical Composition of Romal Albanose [Leucitite]. 
i. 
II. 
I. 
IT. 
SiO 2 
4.6. 24. O. 771 
46.06 
CO 2 . 
A1 2 O 3 
14. 42 . 141 
IO.OI 
TiO 2 
O 77 
Fe 2 O 3 
4. 06 . O25 
7 . 17 
ZrO 2 
FeO 
4.36 .O6l 
?.6i 
P 2 Or 
MeO. . 
6. OQ .17? 
1 4. 74 
SO, 
CaO 
I?. 24 .237 
IO. CC 
Cl. 
Na 2 O 
1.6? .027 
I . 31 
MnO . 
nd 
K 2 O 
6.37 .068 
c . 14 
BaO . 
O T2 
H 2 O + ' . . 
0.78 
1 .44 
SrO . 
Hn 
-57 
IOO.4I 
99-57 
I. Romal albanose [leucitite]. Upper flow of Monte Rado, east of Lake Bolsena, Vulsinian 
District. Washington, analyst. 
II. Missoural albanose [missourite]. Shonkin Creek, Highwood Mountains, Montana. Hurl- 
but, analyst. Pirsson, Bull. U. S. G. S. No. 237, 1905, p. 117. 
Norm of I. 
Lc 
. 20.6? ) 
Ne 
7.67 \ 37 
32 ) 
Di 
. 3? . IO } 
Ol 
77 
Am 
2 O2 ) 
Mt 
? 80 ) , 
11 
. . 2 28 J ^ 
08 
Ap.. 
O.Q7 O 
07 
Rest 
9 8 -93 
I . ?O 
Class.. 
48.82 
Order 
Rang. 
Ratios of 7. 
Sal 
"Fern 
F 
L 
= 0.34 
CaO' 
Subrang 
K 2 O' 
' Na 2 O' 
= 2.52 
100.43 
The analysis in I resembles in general the preceding ones of types of brac- 
cianose, which have also been called leucitite, or leucite-tephrite, but differs in the 
somewhat lower alumina and potash, and in the higher lime. Comparison with the 
missoural type shows the general resemblance and at the same time the much more 
femic character of the latter (the norm of which is published by Pirsson in the paper 
cited). This difference is brought out by comparison of the ratios, especially those 
for class, which in I is almost exactly that of the center point, while in II it is almost 
exactly at the border between Classes I and II. Otherwise both are well within the 
other divisions, the ratios of the alkalis being almost identical. 
Mode. For the same reasons that have obtained before it was impracticable 
to measure the mode of this type optically. It was calculated from the norm as 
usual, the only new assumption being that the small amount of melilite, known to be 
present by microscopical study and indicated by the norm, had the composition 
of that of Monte Somma as analyzed by Bodlander.* In II is given the mode of mis- 
soural albanose [missourite] calculated by Pirsson. f 
* Bodlander, New. Jahrb. I, 1893, p. 17. 
t Pirsson, loc. cit., p. 118. 
