GHOLOGY OR LITTLE ROCKY MOUNTAINS A421 
of egirite, while between the irregular lath-like feldspars occa- 
sional nephelite is seen as a cementing product. The rock powder 
treated with acid is found to gelatinize readily, thus confirming 
the presence of the nephelite; the solution in HNO, reacts 
with silver nitrate for chlorine, but gives no reaction with barium 
chlorides for sulphates, and it is probable that a small amount of 
sodalite is present but no hauyn or nosean. 
The rock is very fresh, an occasional slight kaolinization of 
the feldspar being the only alteration product seen. From the 
association with egirine and nephelite and from the absence of 
any plagioclase, it is clear that the rock is composed chiefly of 
anorthoclase with accessory egirite and nephelite. It thus stands 
closely related to the Sdlvsbergite of Brégger* and is an inter- 
mediate type between that rock and the nephelite rich tinguaites. 
The buttes rising above the mountain slopes near the borders 
of the uplift are laccolithic bodies of porphyry, whose rocks 
present slight differences of character from those of the main 
intrusive mass. The limestone hills at the extreme eastern end 
of the range and Siprary Anne Butte near Landusky may repre- 
sent similar laccolithic bodies, in which erosion has not as yet 
uncovered the eruptive rock. 
Crown Butte is the crag-topped mountain which rises abruptly 
some 600 feet above the town of Landusky. It is composed at 
the base of massive Carboniferous limestone, which forms an 
incurved mass between this butte and that near the Goldbug 
mine. 
The laccolithic mass of porphyry forming Crown Lutte consists 
of a granite porphyry almost identical with that forming the 
main mass of the mountains. Seen in the specimen it is a some- 
what altered porphyry, showing considerable staining due to 
oxidation. The rock is generally of a bluish pink color, showing 
a stony groundmass of a pronounced lavender tint through which 
are scattered numerous flesh-colored phenocrysts of orthoclase, 
with minute crystals of altered micaceous material and occasional 
glassy grains of quartz. 
* Grorudit-Tinguait Serie, p. 67, Christiania, 1894. 
