THE STRATIFIED ROCKS OF ESSEX COUNTY. 43 
secoiul;iry quartz, s(hi]c plagioclase deeply kaolinizecl, 
ground-iuass of kaoliiiite, epidote and magnetite and some 
zoisite in the plane of the bedding. Specimen (tibrolite 
gneiss) collected at INIarble Ridge, south of the railroad 
station : quartz, plagioclaso and orthoclase feldspars in 
grains, large Hakes of muscovite, biotite, and acicular crys- 
tals of fibrolite, in aggregates, scattered through all the 
minerals ; the plagioclase has numerous inclusions of quartz 
and the biotite inclusions of zircons and garnets which 
show fine pleochroic halos. In the ground-mass are patches 
that strongly resemble corderite, but so much altered that 
determination is difficult. In hand specimens this rock is 
nearly identical to the genuine corderite gneiss. 
Hornblende epidote gneiss from Crooked pond, East Box- 
ford ; section across the bedding, microscopic structure : 
green hornblende, twinned feldspar with numerous inclu- 
sions of quartz grains, patches of quartz in which there 
are numerous fluid inclusions, large patches of zoisite, bi- 
otite and magnetite, numerous areas of chlorite and some 
epidote. Section parallel to the bedding shows the zo- 
isite surrounding hornblende crystals and the hornblende 
in turn surrounding grains of magnetite, all lying in one 
j)lane across the section dependent upon one plane of pres- 
sure. Titanic iron surrounded with leucoxene is abundant 
in this section. Specimen from east of Chadwick's pond : 
quartz grains, apparently detrital, with numerous fluid in- 
clusions, much biotite, some plagioclase with inclusions of 
quartz, some chlorite and magnetite. This may be termed 
a biotite schist. Metamorphic hornblende epidote gneiss 
from Smith Mine, Newbury. Microscopic structure of 
section across the bedding : oreen hornblende with numer- 
ous inclusions of plagioclase and magnetite, much biotite, 
some muscovite, grains of quartz showing enlargement by 
the addition of secondary quartz, orthoclase much decom- 
