FETTKE, MANn4^TTAN SCHIST OF NEW YORK 251 



are full of quartz inclusions. A little chlorite derived from altered biotite 

 is also present. 



After crossing the Dover-Pawling Valley, the schists are again exposed 

 overlying the limestone on the east side of the valley. A specimen col- 

 lected from the west slope of Purgatoiy Hill east of Pawling, when ex- 

 amined under the microscope, shows a medium coarse texture and dis- 

 tinctly foliated structure, due chiefly to the parallel orientation of the 

 biotite (PI. XIV, Fig. 5). The mineral composition is principally bio- 

 tite, plagioclase, orthoclase and quartz. The plagioclase is present in 

 large amount. It has a maximum extinction angle of 25°, measured in 

 sections at right angles to the albite lamellae, which would indicate an 

 andesine or acid labradorite variety. A few small garnet grains and some 

 magnetite are also present. The garnet is remarkably free from inclu- 

 sions. 



Another section examined from a specimen collected three and one-half 

 miles east of Pawling shows a coarse-grained crystalline texture and schis- 

 tose structure. It is composed mostly of biotite, feldspar, quartz and 

 garnet. The biotite shows marked pleochroism from light yellowish brown 

 to deep brown. Only minor amounts of muscovite are present. The feld- 

 spar consists mostly of plagioclase with some orthoclase. Considerable 

 quartz is also present. A few small grains of staurolite and a single 

 crytal of tourmaline were also noted in the section examined. 



Going south along the contact of the Dover-Pawling limestone with the 

 overlying schist, the schist does not vary a great deal in composition. In 

 places, quartz becomes more prominent and the amount of feldspar in- 

 creases. 



On the north side of the valley at Haviland Hollow, east of TowTiers, a 

 dense, dark, finely granitoid rock occurs apparently interbedded with the 

 mica schists. It is being quarried for road metal. On examination in 

 thin section under the microscope, the rock is seen to have a granitoid 

 texture and to consist chiefly of the quartz, plagioclase and hornblende. 

 The plagioclase gives extinction angles up to 32° 30' in sections at right 

 angles to the albite lamellae. Some sections do not show the twinning but 

 show good cleavage. They are biaxial and optically positive. The plagio- 

 clase is evidently labradorite. The hornblende shows marked pleochroism 

 from browTiish yellow through deep yellowish brown to dark green. A 

 little biotite is present. Titanite occurs in considerable amount as acces- 

 sor}^ mineral. Magnetite and apatite are other accessory constituents 

 which are present. The rock shows a cataclastic structure, and much of 

 the quartz is undoubtedly of secondary origin. The mineral composition 

 indicates an igneous rock of the composition of a quartz diorite. From 



