. Cecil county . FIG. ROCKS (mETA-RHYOLITE), NEAR BAY FIG. 2.— FALLS OVER GILPIN ROCKS, NEAR HAY VIEW, VIEWS OF PIEDMONT PLATEAU. MARYLAND GEOLOGICAL SURVEY 137 hornblende rapidly increases in amount upon the periphery of thedike and in all altered material. The quartz-feldspar mosaic seems to be an original feature and notdue to the complete crushing of the constituent of an originallycoai se-grained rock, as premised by Dr. Grimsley. A proof of this lies in the presence of uncrushed phenocrysts, some-times with sharp crystal boundaries, which possess inclusions of thefine mo
. Cecil county . FIG. ROCKS (mETA-RHYOLITE), NEAR BAY FIG. 2.— FALLS OVER GILPIN ROCKS, NEAR HAY VIEW, VIEWS OF PIEDMONT PLATEAU. MARYLAND GEOLOGICAL SURVEY 137 hornblende rapidly increases in amount upon the periphery of thedike and in all altered material. The quartz-feldspar mosaic seems to be an original feature and notdue to the complete crushing of the constituent of an originallycoai se-grained rock, as premised by Dr. Grimsley. A proof of this lies in the presence of uncrushed phenocrysts, some-times with sharp crystal boundaries, which possess inclusions of thefine mosaic of the groundmass. Quartz constitutes a considerable proportion of the rock; not farfrom forty per cent when the rock is fresh. Feldspar is somewhat less in amount. It is rarely twinned andis without crystal boundaries. As a constituent of the groundmass,it is too fine-grained for determination. So far as the small, imper-fect and scattering phenocrysts admitted of determination, orthoclase,albite and an acid oligoclase are the species represented. Biotiteocc
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectgeology, bookyear1902
