THE ROMAN COMAGMATIC REGION. 
between the subrangs ciminose (II. 5. 2. 2), where it falls, and that of vicose (II. 
6. 2. 2), so that it should be called strictly a vicose-ciminose. 
Chemical Composition of Martinal Vicose-ciminose \Leucite-tephr ite]. 
CONSTITUENT. 
I. 
CONSTITUENT. 
I. 
SiO 2 
?2. 14 
o.86q 
H 2 O-. . 
O. OQ 
ALO, 
I s . OI 
.i=;6 
CO 2 
.uy 
none 
Fe 2 O 3 
2. IS 
. OIJ. 
TiO 2 
1.22 O 
01 1; 
FeO 
C . IQ 
. 072 
ZrO 2 
trace 
MgO . . 
J.II 
.128 
P,Oc . . 
O. 2A. 
002 
CaO 
8.55 
. 1^3 
SO, . 
0.07 
OOI 
Na 2 O 
I . O2 
. O?I 
MnO . . 
nd 
K 2 O 
7. 2 A. 
.077 
BaO 
o. 20 
H 2 O + 
100.13 
Martinal vicose-ciminose [leucite-tephrite]. Fosso della Parchetta, San Martino, Ciminian Dis 
trict. H. S. Washington, analyst. 
Norm. 
Or 42.81 
Ab 2. 10 
An 13.34 
Ne 7.67 
Di 21.97 I 
01 5-69 ] 
Mt 3.25^ 
II 2.28} 
Ap 0.64 
58-25 
7.67 
27.66 
5-53 
0.64 
Class 
Ratios. 
Sal 
65.92 
33.83 
Order. . 
'Fern 
F 
'L 
= i-95 
Rang 
' + Na 2 O' 
CaO' 
: 7-59 
= 2.25 
Rest. 
99-75 
0.46 
100.25 
Subrang. 
K 2 0' 
'Na 2 O' 
Mode. While the amounts of the phenocrysts of leucite and augite could be 
accurately determined under the microscope, the constituents of the groundmass 
did not lend themselves to determination by Rosiwal's method on account of the 
indefinite character of the salic components, which had to be reckoned together. 
The following were the results obtained: 
Vol. %. Sp. gr. 
Feldspars, etc 47-5 X 2.6 = 
Leucite phenocrysts 11.2 X 2.5 = 
Augite phenocrysts 12. 2 X 3.3 = 
Augite in groundmass 15.6 X 3.3 = 
Magnetite 3.5 X 5.2 = 
100.0 287.4 99-9 
In calculating the mode from the norm it was assumed that no nephelite was 
present, and that^the alkali-feldspar had the composition G^Abx. The assump- 
tion was made in regard to this rather than to the soda-lima feldspar, since it was 
difficult, if not impossible, to determine the average composition of this latter opti- 
cally. The calculated composition of Ab 4 An 3 , an andesine, agrees as well as could 
be expected with the appearance under the microscope. The calculated mode is 
as follows: 
149-5 
28.0 
40.3 
5-4 
18.2 
Wt. %. 
52.0 
9-7 
14 o 
17.9 
6-3 
