216 Collie—Geology of Conanicut Island, R. I. 
In all cases the coarser grains are either flattened out or else 
crushed to a mosaic. All stages of the process of breaking 
down are represented, from the slight fracturing of the grain, 
through the stage of peripheral granulation to complete crushing. 
The constituent grains are stretched out parallel to the press¬ 
ure, and where they cross the apexes of folds are bent or broken. 
Ilmenite plates and sericite flakes are bent and twisted about 
the broken grains of quartz and feldspar. 
Andalusite occurs in large crystals sometimes 7 or 8 inches 
in length. Garnets are very abundant in the dark schists, they 
are usually changed in whole or in part to chlorite. They are 
almost invariably more or less crushed tailing out at each side 
and forming typical augen structure. About these lenticular 
bodies, the sericite is arranged in curves which are determined 
by the form of the included crystal. In the immediate vicinity 
of the garnets there is a greater development of sericite than 
elsewhere. The schistosity is very perfect and the sericite fibres 
are oriented parallel to it except where they are compelled to 
change their direction on account of inclusions. Planes of part¬ 
ing are very frequent in the microscopic sections, these are 
frequently gliding planes shearing movements taking place 
along these. Sericite is more abundantly developed on these 
planes than elsewhere in the rock. These planes often pass di¬ 
rectly through the garnet grains instead of passing around them 
though the latter method of occurrence is the more common. 
The light schists .— The light colored schists so closely re¬ 
semble the dark schists that no separate description is necessary. 
The only marked difference is the great amount of fine rutile 
needles which are often found in the former, occurring in nests 
or compact felt-like masses. 
The schists of the northern portion of the island are more 
metamorphosed on the west side than on the east, there is a 
progressive development of schistosity apparent even within 
the narrow limits afforded by the width of the island. The 
total thickness of the schists is estimated at 1,200 feet. In 
order to set forth more clearly the variety of formations pres¬ 
ent in the schist series, a section from one of the low cliffs on 
the west shore will be described. The rocks exposed in this 
