948 THE JOURNAL OF GEOLOGY. 
The rocks of analyses 1 and 2 form dikes; the first occur- 
ring on the divide between Lamar River and Crandall Creek, 
and the second on the south slope of Hoodoo Mountain. The 
two dikes trend in the same direction and are possibly one con- 
tinuous body. The rocks are alike chemically and mineralogic- 
ally and may be described together. They are light gray and 
aphanitic, with a waxy luster. There are prominent phenocrysts 
of augite and rusted spots of serpentinized olivine, but none of 
feldspar. In the rock from Hoodoo Mountain there are amyg- 
dules of white stellate zeolite. In thin section the rocks are seen 
to be holocrystalline with more feldspar than ferromagnesian 
minerals. The feldspars are in part lath-shaped, in part tabular. 
They are simple twins, and are orthoclase with kernels of plagio- 
clase which is mostly altered, the centers of the crystals being 
decomposed in many cases. There is considerable serpentine 
scattered through the rock. The ferromagnesian minerals are 
augite, biotite, magnetite, with some ilmenite in rod-like shapes. 
Apatite occurs in needles. There is considerable analcite, which 
partly occupies former cavities or cracks, and partly has outlines 
suggesting former isometric minerals. The dike on the divide 
at the head of Lamar River is immediately alongside of the dike 
of absarokite whose chemical composition is given by analysis 2 
of Table I. 
The rock of analysis 3 is quite similar to those just described 
but is still more feldspathic. It forms a dike in the Ishawooa 
Canyon. It is dark gray and waxy looking with tabular pheno- 
crysts of feldspar and many smaller ones. It is holocrystalline, 
and consists of abundant lath-shaped twins of orthoclase having 
a rectangular kernel of labradorite, whose symmetrical extinc- 
tion angles correspond to a composition of An, Ab,. There is 
an isotropic cement between the feldspars which may be analcite 
or sodalite. Biotite and augite are abundant in small crystals, 
besides magnetite and a little serpentine, which appears to have 
been derived from small olivines. The phenocrysts are labrodorite 
(An, Ab, ), some of which have borders of orthoclase. Sodalite 
is possibly present among the phenocrysts. 
