ON CORUNDUM -SYENITE FROM MONTANA 



751 



in which x is the albite molecule and y the nephelite molecule. The 

 remaining alumina goes into the corundum molecule. 



Total 



99-5 



The classification of the rock according to the new quantitative 

 system is as follows: 



Sal 

 Fem 

 F+L 

 C+Z 

 L 

 F 

 K 2 (y+Na 2 0' 



CaO' 

 K 2 Q' 

 Na 2 0' 



95-9 > 7 

 3.6 1 



64.0 7 s 

 = - ± — >-< 2 

 31-9 1 3 



2.3 1 



62.7 7 



123 ^7 



o 1 



Class I, Persalone 

 Subclass II, Persalone 

 Order 5, Perfelic 

 Rang 1, Peralkalic 



-7 — >-< - Subrang 3, Sodipotassic 



The magmatic name of this subrang is uralose and the magmatic 

 symbol I 2 , 5, 1, 3. Only two rocks have previously been assigned 1 

 to uralose, a corundum-syenite and a corundum-pegmatite, both 

 from the Urals. 



Washington, Professional Paper, U.S.G.S., No. 14, 217 (1903). 



