GEOLOGY OF SARATOGA SPRINGS AND VICINITY 7I 



number of plagioclase grains, rarely one of microcline, in a cement of sericite 

 with some calcite and small areas of secondary quartz. There are large 

 scales of muscovite and of a chloritic mineral, scarcely dichroic, and under 

 polarized light a bluish green or prussian blue, with little or no change in 

 rotation. More conspicuous and typical of the rock are scales from 0.043 to 

 0.130 by 0.020 millimeter, frequently bent, pale green, markedly dichroic, and 

 under polarized light olive or slightly bluish green. These scales contain 

 bands of a colorless mineral parallel to their cleavage, which measure 0.0043 

 in width and polarize in brilliant orange, emerald or blue. Extinction in 

 both about (if not quite) parallel to cleavage and bands. Finally, there are 

 grains or crystals of a muddy yellow under incident light, probably limonite 

 and that after hematite. The scales of hematite, sometimes graphite, can be 

 made out with a magnifying glass. 



This characteristic rock can usually be identified at a distance by the 

 peculiar pale brick-red color of its weathered surface, and, on closer in- 

 spection, by the minute spangles and the olive color of the fresh surface. 



The olive grit has not furnished any fossils, but it was found 

 full of carbonaceous blotches, suggesting seaweeds, and large worm 

 trails. It is apparently a shallow water deposit. 



The belts of heavier grit beds alternate with belts of more slaty, 

 often brownish weathering beds, apparently resulting from the grit 

 through a stronger development of the cleavage. These belts were 

 found to be worn down more, forming the depressions between the 

 ridges of harder grit. 



The hills composed of this rock are frequently discerned from a 

 distance through the reddish color of the soil they furnish. The 

 Georgian limestones were also found to weather into soils of reddish 

 tints so that as a whole the Georgian areas of this region can, to a 

 large degree, be distinguished from the Ordovicic shale areas by 

 the soils, wherever the drift is thin or its lower portion exposed, for, 

 as a rule, this also contains so much material derived from the under- 

 lying rocks that it partakes of the reddish color. The olive grit forms 

 a belt beginning at the projecting southeast corner of the Georgian 

 area south of Louse hill, continuing over Louse hill and exposed 

 on its north slope, on the banks of the Batten kill, continuing north 

 of Greenwich to the central and eastern peaks of the Bald mountain 

 ridge. - - 



South and east of Louse hill the olive grit or the Bomoseen is 

 flanked by massive ledges of gray quartzite speckled with brown 

 spots of limonite. We consider this bed as corresponding to the 

 massive beds of quartzite found farther east by Dale in association 

 with the Bomoseen grit. On the centre peak of Bald mountain, the 

 Bomoseen grit is flanked on both sides by quartzite beds which are 



