

Ill THE CRYSTALLINE BOOKS OF CECIL COUNTY 



Creek, and in a northeast-southwest line from this point, the mica- 

 gneiss shows a conglomeratic phase. It is thoroughly crystalline and 

 schistose, a rather fine-grained aggregate of muscovite, quartz and 

 feldspar, with secondary chlorite and epidote. The traces of quartz 

 and gneissic pebbles can be distinctly seen in the hand specimen. 

 The slides show muscovite in considerable plates and also in minute 

 scaly aggregates. There are rounded quartz and feldspar grains, 

 these latter altered to muscovite. Green scaly biotite and muscovite 

 are wrapped about these grains, making the gneissoid conglomeratic 

 character very conspicuous in the slide. Rounded apatites are also 

 present and more or less magnetite. The feldspar is both orthoclase 

 and plagioclase, and in some slides, is in about equal proportion with 

 the quartz, but never predominates. Epidote is an insignificant 

 secondary constituent, more or less confined to cracks. 



Xot more than one-fourth of a mile northeast of Bald Friar, the 

 rock shows the same constituents as at the locality just described, 

 but is somewhat coarser grained. The microscope shows large plates 

 of muscovite and yellowish brown biotite. The feldspar is orthoclase, 

 microcline and andesine-labradorite, and about equals the quartz in 

 amount. Rounded apatites are also present. 



The eastern area of mica-gneiss is represented by slides from only 

 two localities: on Big Elk Creek, one and a half miles northwest of 

 Appleton, and about one mile north of Eair Hill. At the former 

 locality the rock is very micaceous and contains so much pegmatitic 

 material in parallel planes that it resembles an impregnation gneiss. 

 It is coarse-grained, and hand specimen and slides show much brown 

 biotite, some muscovite, fresh quartz with little feldspar, or with 

 feldspar equalling the quartz in amount. Both plagioclase and or- 

 thoclase feldspar are present. The structure is thoroughly gneissic. 



At the latter locality quartz and feldspar bands alternate with the 

 scales of brown biotite, which lie with their longer axes parallel to 

 the banding. 



The mica-gneiss included within the granite-gneiss and outcropping 

 on the Susquehanna river, is a fine-grained grey schistose rock. It 

 is composed chiefly of quartz and mica. The mica is both biotite 



