ABSAROKITE-SHOSHONITE-BANAKITE SERIES. 939 
I. Leucite-absarokite, Ishawooa Canyon, Wyoming—analyzed by J. E. Whit- 
field. 
. Absarokite, dike at head of Lamar River—analyzed by L. G. Eakins. 
. Absarokite, dike south of Clark’s Fork River-—analyzed by L. G. Eakins. 
. Absarokite, lava flow, head of Raven Creek—analyzed by L. G. Eakins. 
. Absarokite, dike, divide east of Cache Creek—analyzed by L. G. Eakins. 
me WH N 
The five analyses are arranged according to decreasing per- 
centage of magnesia, the range being a little more than 5 per cent. 
The alumina increases, the range being less than 2 per cent. 
Potash increases through a range of 2.6 per cent., while soda 
and lime have a still smaller range. The second, third and 
fourth analyses are closely alike. The first and fifth are not so 
much alike that they might not be considered separately; the 
chief differences being in magnesia and alkalies. But they are 
related in other respects. They all exhibit considerable loss 
upon ignition, corresponding to the amount of hydration due to 
alteration, or to the presence of zeolitic minerals. 
As already remarked the rocks differ somewhat in the min- 
eral composition of the groundmass, as well as in its microstruc- 
ture. That with the coarsest grain is the one whose chemical com- 
position is given by the first analysis. It was not found in place, 
so that its exact mode of occurrence is not known, but it is prob- 
ably an intrusive mass or dike in Ishawooa Canyon, Wyoming. It 
has already been described by Mr. Hague." It consists of abundant 
phenocrysts of olivine and augite, 3™™ in diameter, and of a sub- 
ordinate amount of gray crystalline groundmass. In thin section 
the olivine is colorless and free from inclusions. The augite is 
pale green, with high extinction angle, reaching 42°. It encloses 
some olivine and magnetite. The form of these phenocrysts is 
only partially idiomorphic, the outline being jagged in some 
cases; the reéntrant angles being occupied by small crystals of 
orthoclase, whose formation must have been at least contempo- 
raneous with the crystallization of the margins of the olivine and 
augite. The groundmass consists of crystals of orthoclase and 
leucite, which are in part idiomorphic, although the mass is holo- 
* HAGUE, A. Notes on the occurrence of a leucite rock in the Absaroka Range, 
Wyoming Territory, Am. Jour. Sci., Vol. XXXVIIL., July, 1889. 
