AN ANALCITE-BASALT FROM COLORADO 687 
amount and composition of the portion of the rock soluble in 
hydrochloric acid is shown in column II. The augite was, in 
the main, so free from inclusions that an analysis was made by 
Dr. Hillebrand for comparison with other rock augites. The 
material was isolated by the Thoulet solution, and was found to 
be very pure on microscopical examination. III is the analysis 
of the augite. 
I Ja II Ill 
SHO 51.24 854 21.97 49.26 
AOE 153 
Al,O, 24.00 235 9.943 6.01 
FeO, 1.204 Syria: SS 
FeO 4223 
CaO 1.62 29 1.95 21.79 
SrO .06 08 06 
BaO ? ? 
MgO ie 8 2.87 12.40 
KO gals 13 56 41 
Na,O II.61 187 4.04 79 
H,O .627 3.915 
H,O 8.47? 470 
BeOr 
SOF none 
Cl trace 05 
100.40 49.08 99-79 
WOver HsSO,. 3 Includes P,O;. 5 Assumed from rock analysis. 
2 Remainder of water. 4 Total iron as Fe,O3. 
The isotropic mineral could not be secured entirely free 
from attached or included particles of doubly refracting sub- 
stances. But these made up a small part of the material sub- 
jected to analysis. After treatment with hydrochloric acid 
there remained an insoluble residue, amounting to 4.22 per cent. 
of the substance taken, and this was found on microscopical 
examination to consist of augite and feldspar. From the molec- 
ular ratio the following proportion may be derived: 
SiO5 Al, On Ro Or Oh: 85 40235n-.287 2 470. oF 
2:6 = vewlbeeee oT? 2 
In this result CaO and MgO are united with the alkalis and iron 
