PETROGRAPHY. 
127 
parison is also given the only other known analysis of a rock of the same subrang, 
a "ouachitite" from a dike near Hot Springs in Arkansas. According to Kemp's 
description* this is highly biotitic and is to be regarded as a distinct type, to which 
the name of ouachital fiasconose may be given. An analysis of a rock from Mon- 
tana belonging to a closely related magma, described by Pirsson, to which the type 
name of arrowal cascadose may be given, will be found in III. 
Chemical Composition of Fiordinal Fiasconose [Leucite-basanite\. 
I. 
II. 
III. 
SiO 2 
4.4.80 o 
748 
36.4O 
46 04 
A1 2 O 3 
12. 73 
I2? 
12 .04 
12. 23 
Fe 2 O,. 
3. 31 
O2 1 
8.27 
3.86 
FeO 
4- 3 1 ? 
06 1 
4- ^0 
4.60 
MgO. . 
13-71 
343 
II .44 
10. 38 
CaO 
12.85 
231 
14.46 
8.Q7 
Na 2 O 
1 .02 
OI7 
O.Q7 
2.42 
K 2 O 
3.66 
O30 
3.OI 
e. 77 
H 2 O + 
i . lo 
) 
H 2 O 
O. 27 
2.36 
2.87 
CO 2 
none 
3.04 
TiO 2 
O.Q? 
OI2 
0.42 
0.64 
ZrO 2 
trace 
P 2 O S 
O. 23 
OO2 
1 .04 
1. 14 
SO 3 
none 
trace 
Cl 
O. II 
Cr 2 O,. 
0.03 
MnO 
n.d. 
n.d. 
trace 
BaO 
0.08 
0.48 
SrO 
0.25 
99-77 
99.84 
99.76 
I. Fiordinal fiasconose (leucite-basanite). Fiordine, near Montefiascone, Vulsinian District. 
Washington, analyst. 
II. Ouachital fiasconose (ouachitite). Dike 18, near Hot Springs, Arkansas. Eakins, analyst. 
J. F. Williams, Ann. Rep. Geol. Surv. Ark., 1890, II, p. 399. 
III. Arrowal cascadose (minette). Dike near Arrow Peak, Highwood Mountains, Montana. 
Foote, analyst. L. V. Pirsson, Bull. U. S. G. S. No. 237, 1905, p. 145. 
Ratios of I. 
Sal 
Class 
41.14 
Or . . 
Norm of I. 
. O.C6) 
An 
19.18) 
I9-74) 
L C 
. .16. 57 ) 
Ne 
4-83 \ 
21.40) 
Di 
33 . 86 ) 
01 
. .i?. 63 ) 
49.49 
Mt 
4-87) 
11 
. i . 82 S 
6.69 
Ap. . 
. O. 6^ 
0.63 
Rest 
97-95 
1.86 
Fern 
= o. 72 
Order 
56.81 
Rang. 
Subrang 
F 
"L 
K 2 O' + Na 2 O' 
CaO' 
K 2 0' 
= 0.92 
= 0.81 
'Na 2 O' 
= 2.29 
99.81 
The analysis shown in I is remarkable as being the lowest in silica, alumina, 
and potash, and the highest in magnesia and lime, of any of the rocks analyzed. As 
* Kemp, In Williams, Ann. Rep. Geol. Surv. Ark., II, 1890, pp. 393 ff. 
