412 WEED AND PIRSSON 
the basal bed of the Cambrian series. This breccia occurs in 
rough, craggy masses on the slope immediately above the mine. 
The crest of the ridge above the mine is formed ofa breccia 
composed of pieces of porphyry in which no quartzite was 
noticed. At this locality the crest of a lateral ridge north of 
the mineralized belt is formed of a fairly dense porphyry, which 
is somewhat brecciated, is mineralized, and generally of a light 
Antoine tutte. Granite butte. 
a 
ABOVE SEALEVEL 
f 
i 
Fic. 3.—a@— Crystalline Schists; 6 = Granite Porphyry; c=Cambrian; d= 
Siluro-Devonian; e = Carboniferous; f = Mesozoic. 
purple or reddish color, the rock carrying about $2.50 in free 
gold per ton. West of the Goldbug mine the same brecciated 
porphyry occurs, with the quartzite above it dipping west, and 
the Cambrian limestones, conglomerates, and shales which 
occur at this place are somewhat baked and indurated. It is 
believed that the breccias near this Goldbug property mark the 
point of eruption of the porphyry magma. This is strengthened 
by the baking of the sedimentary rocks in contact with. this 
breccia on the west. 
Contact metamorplism—Throughout the Little Rocky Moun- 
tains there is but little contact phenomena to be noticed in the 
sedimentary rocks about the porphyry intrusions. The only 
place where this action was noticeable is in the vicinity of the 
Goldbug mine, where the induration and consequent different 
fracture and weathering of the sedimentary rocks adjacent to the 
porphyry mass is quite marked, although it is here but a few 
yards in extent. Elsewhere throughout the mountains no con- 
tact metamorphism of any consequence was observed, not even 
where the intrusive rocks have come in contact with the Creta- 
ceous shales or the massive Carboniferous limestones, as they do 
in Crown Butte and in the eminence west of Mission Butte. 
Petrography —The main mass of the mountains, including the 
