Microscopic Descriptions of the Schists. 217 
section are representative of the whole series. The lowest 
number, between two and three feet in thickness, is extremely 
rich in graphite and contains large garnet inclusions, flakes of 
magnetite are abundant, ilmenite and its decomposition product 
leucoxene occur more sparingly, the rock is extremely soft, 
finely schistose and in some localities is so rich in parti¬ 
cles of carbon as to resemble coal. This schist is overlaid by a 
fine grit, a few inches in thickness, and chiefly of interest be¬ 
cause it contains fragments of the underlying rock, there being 
a slight unconformity between the formations. The third mem¬ 
ber of the series is a fine grained dark gray schist with large 
garnet inclusions. The ground mass consists of fine clastic 
grains of quartz and feldspar, which closely interlock. 
Ilmenite, magnetite and graphite are very abundant. This bed 
contains considerable ottrelite, an occurrence which will be more 
fully described later. 
The next higher formation is a thin bed of carbonaceous 
schist, with schistosity remarkably developed. Long narrow 
ilmenite plates and numerous rose colored garnets characterize 
the rock. The main mass of the rock consists of very fine 
sericite flakes all arranged parallel to the schistosity. The 
graphite being intimately mixed with the sericite, not as is 
frequently the case collected into masses. There is a greater 
amount of feldspar in the rock than usual and a greater 
difference in the size of the quartz grains than is wont to be 
the case. Biotite which is abundant, adds to the schistose char¬ 
acter of the rock. Succeeding this bed is a layer of iron gray 
schists, tending to assume gritty characteristics. This forma¬ 
tion is richer in varied mineral constituents than any other on 
the island. It contains ilmenite, fine flakes of biotite and 
hornblende, garnets, staurolite, chlorite, zircon, graphite and 
rutile. Quartz grains are numerous and the rock is not as 
finely schistose as the more feldspathic varieties. If feldspar is 
abundant, schistosity is well developed, but in proportion as 
quartz enters into the composition of the rocks, schistosity dis¬ 
appears. Evidences of dynamic force are clearly shown in these 
more quartzose rocks, because the crushing of the grains is 
more apparent, than in the case of other minerals. 
