132 
G. T. PRIOR. 
brown hornblende. Some of the felspar-plienocrysts are much decomposed, but show a 
narrow margin of quite unaltered material. 
A chemical analysis of specimen 714 from G 3 gave the following result under I 
I. 
Ia 
11. 
III. 
(714.) 
mol. ratios. 
(Banakite.) 
mean of— (1) and (5), (p. 119) 
Si0 2 
: 
48-22 
•804 
51-46 
49-11 
TiOo 
- 
2-09 
•026 
0-83 
3-06 
A1.A 
= 
18-47 
•181 
18-32 
19-10 
Fe 2 0 3 
= 
5-28 
•033 
4-61 
2-22 
FeO 
= • 
3-90 
•051 
2-71 
6-78 
MnO 
= 
o-io 
•001 
0-17 
0-08 
CaO 
6-02 
•108 
6-03 
6‘75 
MgO 
:: 
2-07 
•052 
2-91 
5-36 
Na 2 0 
= 
4-94 
•080 
4-11 
5-30 
K.,0 
= 
3-47 
•037 
4.48 
2-85 
PA 
= 
0-88 
•006 
0-86 
0-39 
H.,0 at 110° 
— 
0-44 
ILO above 110° 
2-89 
} 
3-89 
C0 2 and loss 
= 
(1-23) 
100-00 100-38 
The Osann formula of this rock is : — 
S 60'44 a n\ Gi/ll 
The formula for a banakite-dyke from Ishawooa Canyon, Wyoming,* the analysis 
of which is given under II, is : — - 
S 60 01 Chi ?? 6 ' 8 ' 
Calculation of the “ norm ” gave the following result : — 
KAlSi.,0, 
= 20-57 
NaAlSi/R 
= 25-15 
NaAlSiO, 
= 8-90 
CaALSi.A 
= 17-79 
CaSi0 3 
= 3-12 
FeSi0 3 
= 3-30 
MgSiO s 
II 
to 
o 
Fe 2 0 3 
II 
Cl 
rc 
GC 
FeO.TiO., 
= 3-95 
Ca 3 2P0 4 
= 1-86 
In the American quantitative system, the rock would be classed as Akerose, but 
a very slight difference in the ratio 
K 2 0 -f- Na 2 0 
~ CaO 
would refer it to Shoshonose, like the 
kersantite described above (p. 130). 
Under III is appended the result of taking the mean of analyses (l) and (5) (see 
p. 119) of the olivine-basalt (656) and the leucite-kenyte (818) of the Eoss Archipelago. 
Although it may have no real significance, it seems worthy of note that the chemical 
composition of this ancient dyke-rock (714) should be so near the mean of the two 
Idlings, Monogr. U.S. Gcol. Surv., 1899, No. 32, Tart II, p. 347. Analysis by Eakins. 
