249 
The composition of the rock is, therefore, as follows : 
50°46 Albite. 
45°49 Quartz. 
0:30 Silica soluble. 
1:14 Water. 
2°91 Bases dissolved (3:14 less 0°23.) 
100.30 
8. Coarse-grained, red, yielding a red powder. 
89°58 Insoluble in acid. 
73°37 Si03(73°79—0°42) 
16:21 Bases combined with Silica. 
Undissolved bases and combined with silica. 
Al.O3 = 9:92 
NaO = 6:08 
16:00 
There is a sufficient correspondence between these two 
figures. The amount of alumina required by the soda would 
be 10°10 p. c instead of 9°92 which agrees almost exactly 
again, so that we have for albite. 
Al,O; =9:92=Si0;=26:'00 
NaO'=6-08—= “ = 885 
16:00 34°83 
16:00 
50°83 Albite. 
The quantity of quartz is found to be 
89°58 Insoluble in acid, 
50°83 Albite. 73°37 Silica total. 
34°83 Silica of Albite. 
88°75 
0°21 38°54 Quartz. 
38°54 Quartz. 
