210 
Collie—Geology of Conanicut Island , R. I. 
iferous in age; this is indicated in a twofold way. First, plant 
remains of carboniferous age are found occasionally in the lower 
beds of the series; second, the trend of the rocks carries them 
into the coal bearing series of rocks a few miles to the north¬ 
east. The schists are of two types; the first is a light gray 
rock tinged with green and possessing a bright micaceous lustre, 
when wet it is greasy to the touch and readily crumbles, but nor¬ 
mally it is hard and brittle, its schistosity is developed in an ex¬ 
treme manner and the rock readily splits along the schistose planes. 
The second type is a dark, colored rock, containing a large per¬ 
centage of graphite and other forms of carbonaceous mater¬ 
ials. It is essentially like the light schist in structure, the 
chief difference being the larger amount of carbonaceous matter 
present. The schists are usually made up of finely comminuted 
materials, though more or less grit and even fine conglomerate 
occurs interbedded with the schist series. The schists im¬ 
mediately north of the granite are of the first named variety, 
they extend for a mile or more before being replaced by the 
darker variety, though occasional bands of dark schist are inter¬ 
bedded between the beds of light schist. The strike of the 
schist immediately north of the granite, in common with the 
mass of this formation on the island is N. N. E., S. S. W., with 
the dip generally S. E. The dip of the schistosity varies greatly, 
out it is frequently to the N. W. and S. E. It often accords 
with the dip of the rocks. 
The bedding is frequently very obscure and it is difficult at 
all times to determine it, hence the relationship of schistosity 
and bedding is not at all times traceable. In contrast to the 
majority of the schists, the light gray schist of this neighbor¬ 
hood contains few inclusions. Those that occur are largely 
•iderite or pyrite, fine flakes of carbonaceous matter are dissem¬ 
inated through the rock, and where this matter increases in 
amount, a darker hue is given to the rock. Chlorite and 
muscovite occur abundantly. The major portion of the rock 
consists of feldspar, finely grained and distinctly clastic in char¬ 
acter, dull in appearance even when most unaltered. It is 
kaolinized to some extent, often altered to chlorite or muscovite, 
but the larger portion of the feldspar has been altered to seri- 
