QUARTZ-MICA SCHIST 



381 



Figure 3. — Photomicrograph of Quartz-mica Schist icith SilUmanite. X Nicols. (X 20) 



Locality, 1% miles northeast of Mountainville, Allentown quadrangle. Specimen 7323. 

 The sillimanite shows mesh-structure owing to alteration to pinite along transverse 

 cracks ; the bulk of the field is occupied by sericite, with a few irregular grains of quartz. 



Figure 4. — Photomicrograph of Quartz-mica Schist tvith Garnet. Ordinary Light. 



(X 20) 



Locality, 1 mile north of Springtown, Allentown quadrangle. Specimen 253. The 

 bulk of the field is occupied by garnet; it contains numerous inclusions of clear quartz 

 and a few mottled gray patches of micaceous material. 



Figure 5. — Photomicrograph of Quartz-mica Schist shoicing rounded Zircons. Ordinary 



Light. (X 100) 



Locality, east edge of Allentown quadrangle. Specimen G396. The clear pale gray 

 areas are quartz ; the Y-shaped mass in the center is sericite ; round zircons of all sizes 

 standing out in relief are to be seen around the right-hand arm of the Y. 



Figure 6. — Photomicrograph of Oranite, shoioing angular Zircons, for Comparison. 

 Ordinary Light. (X 100) 



Locality, ridge southeast of Lower Saucon, Allentown (juadrangle. Specimen GSGO. 

 Two attached zircon crystals api)ear near the center; they show distinct angular outline. 



