218 
Collie—Geology of Conanicut Island , R. I. 
The next higher rock is microscopically similar to the black 
carbonaceous schists already noted. The rock is markedly 
schistose and garnetiferous. The schistosity curves gracefully 
about the crystals of garnet which are rarely crushed to a 
mosaic and drawn out into augen. The rock is not as 
completely metamorphosed as many rocks of the series, and this 
is shown by the incomplete fracturing of the garnets, by the 
lenticular, not flattened, condition of the augen and by the con¬ 
dition of the garnets which are unusually fresh and unchanged. 
Graphite in this formation occurs included in the garnets and 
also as a zone about them. The following member of the 
series is another dark gray schist, containing small garnets, 
magnetite and graphite. Quartz is the chief constituent, the 
grains are fine and uniform in size and are flattened out parallel 
to the schistosity. At intervals there are slight folds, the 
the force which produced them was later than the schistosity 
because the quartz grains in the neighborhood are disturbed and 
turned from their alignment, which is so perfect in other parts 
parts of the section. When examined microscopically these dis¬ 
turbed grains are found to extinguish later than other portions 
of the rock, which shows that they have been crowded out of 
parallelism with the other constituents of the rock. The last 
member of this particular section is a fine carbonaceous schist 
with a metallic lustre and very rich in garnets. Microscopic¬ 
ally this schist is shown to be a fine grit, containing fragments 
of a yet finer grit. The materials of this rock are greatly com¬ 
pressed. The flattening of the uniform quartz grains is excess¬ 
ive, and yet so regular is their arrangement that they seem to be 
placed in position by human hands. The rock has been slightly 
folded, the long ilmenite plates are bent about the garnets and 
the secondary chlorite is twisted into confused and intricate 
patterns. 
This enumeration of the schistose beds might go on indefi¬ 
nitely. Enough has been said to indicate their general charac¬ 
ter. They consist largely of alternating carbonaceous schists 
and fine grits. The structure of these beds indicates that there 
was a frequent change of conditions in the deposition. Fine 
sediments were laid down, then accompanied, doubtless, by a 
