954 THE JOURNAL OF GEOLOGY. 
with very high potash. In these two cases we find shonkinites 
as extreme forms of differentations in connection with syenitic 
rocks quite different from one another in chemical composition, 
one being comparatively low in alumina and the other high, 
the sum of the alkalies in one case being 8.85 per cent., and in 
the other 12.74 per cent. In each instance the associated rocks 
are facies of one igneous mass. 
‘TABLE V. CHEMICAL ANALYSES OF IGNEOUS ROCKS FROM YOGO 
PEAK AND SQUARE BUTTE, MONTANA. 
Yogo Peak. Square Butte. 
(Pane SS aR 
I 2 3 4 5 
SiO. - - - 61.65 54.42 48.98 46.73 56.45 
TWO, - - 56 .80 1.44 78 .29 
Al,O3 - - - 15.07 14.28 12.29 10.05 20.08 
Fe.0O3; - - 2.03 Bae2 2.88 3.53 1.31 
HeOur- - 2) Py A103} 5o77/ 8.20 4.39 
MnO - - .09 .10 .08 28 .09 
MgO - - =) 93:67. 6.12 9.19 9.68 63 
‘CaO - - 4.61 TE. 9.65 13.22 Paine 
BaO_ - - - 7] 32 43 Ras Goac 
Na,O - - 4.35 3.44 QnoD 1.81 5.61 
K,O - + - 4.50 4.22 4.96 3.76 Vien? 
P.O; - - 33 59 .98 1.51 53) 
‘Cr,O; - - tr. tr. tr. 
SrO - - .10 13 .08 aan 
Li,O - - - tr. tr. tr. tr. soo 
Fl - 2 s 6000 esate ‘22 Cl .18 43 
H,O at 110° = 26) 22 .26 on 1.77 
H,O above 110° PASI 38 56 
100.15 100.19 99-99 100.97 100.45 
O=F1 .08 O=Cl .04 .10 
99.91 100.93 100.35 
I. Syenite, Yogo Peak, analyzed by W. F. Hillebrand. 
. Yogoite, Yogo Peak, analyzed by W. F. Hillebrand. 
. Shonkinite, Yogo Peak, analyzed by W. F. Hillebrand. 
. Shonkinite, Square Butte, analyzed by L. V. Pirsson. 
. Sodalite-syenite, Square Butte, analyzed by W. H. Melville. 
Mm & WwW Wd 
