THE STRATIFIED ROCKS OF ESSEX COUNTY. 35 
an abiiiulance of magnotite and some limonitc. The dis- 
integration of this rock produces the magnetite and garnet 
sand of the region. The mica schist of Nangns Head, 
Marblehead, and Wood luiry's Point, Beverly, probably be- 
long to this metamoi-phic slate although the metamorphism 
is moi-e complete ; for, in these last named outcrops, the 
schist is not only cut by the granite but it is also cut by 
the diorite, elneolite zircon syenite, felsite and diabase 
dykes, thus making the metamorphism of the rock-mass 
most intricate ; indeed, as pointed out by Dr. M. E. Wads- 
Avorth, the elEeolite zircon syenite has been injected in 
large sheets into these schists, in the planes of the schist- 
osity and jointings of this rock, to such an extent that in 
some places it is puzzling to decide which is syenite and 
which is mica schist. 
Microscopical examination shows this schist to be com- 
posed of a few grains of clastic quartz sand, much secon- 
dary quartz, secondary glassy feldspars, some muscovite, 
an abundance of l)iotite which is probably secondary, a few 
gi'ains of epidote, apatite as inclusions in the ground-mass 
which is feebly polarizing earthy kaolin, much magnetite, 
red garnets and micro-zircons. 
In Middletcm, half a mile southeast of the village, near 
the house of Mr. J. U. Parker, is a well preserved clastic 
shale approaching a sandstone. This outcrop shows a strike 
nearly northeast to southwest with the dip 50° north of 
west ; it is again seen in an outcrop in the rear or west side 
of the barn of Mr. Francis Peabody near the Ipswich river 
on the north side of the village. The microscopic structure 
of this shale is : angular and rounded grains of quartz which 
show embryonic cracks and much crushing and in some 
grains a secondary enlargement, plagioclase twinned feld- 
spars broken and crushed, some of which are in well-round- 
ed grains ; ground-mass an earthy kaolin with plates of bi- 
