48 NEW YORK STATE MX'SEUM 



Near the railroad track and again on the 480-foot knoll four- 

 tenths of a mile east of the mouth of the small tributary entering 

 the Grass river from the southeast at a point one and eight-tenths 

 m.iles below the trestle, are found outcrops of a white vitreous 

 quartzite similar to the larger occurrence hrst described. The sec- 

 ond of these is also capped by a remnant of Potsdam conglomerate. 

 The shape and geological relations of both of these bodies are, how- 

 ever, unknown, and they are therefore conventionally mapped as 

 separate lenticular masses. Quartzite being in general a brittle 

 formation, and under conditions of crustal deformation a much 

 more competent member than the associated Grenville limestone, it 

 is thought not unlikely that these various occurrences are actually 

 distinct, and that if the formation was originally continuous, it has 

 been broken into a number of pieces and the intervening spaces 

 filled with the more plastic limestone. 



Occasionally a thinner layer 8 to 10 inches thick is found inter- 

 banded (tliat is, interbedded) with other thin-bedded micaceous 

 schistose material, representing in all probability the metamorphosed 

 equivalents of a series of alternating sandy and shaly strata. The 

 most interesting observed example of such thin interbedded quartz- 

 ose layers is shown in a section exposed on the right bank of the 

 Grass river at the north edge of Canton village. The beds dip 15° 

 northeast and exhibit the following succession, from below upward : 

 8 feet of impure micaceous gneiss. The laminations in the 

 lower part of the stratum average i inch in thickness, in the" 

 upper part 8 to 12 inches. Xear the top are a number of 

 nodules or discs of radiating pyrite i inch in diameter. 



8 inches of light gray laminated quartzite. 



9 inches of impure greenish-gray micaceous material. 



3 feet of massive quartzitic beds with a i>< inch quartz layer 

 at the bottom. 

 A thin section shows the upper siliceous stratum to be composed 

 of predominating quartz, to whose ver\- pronounced recrv'stallization 

 in parallel and elongated elliptical and subelliptical anhedra is due 

 the foliation of the rock. Orthoclase and acid andesine interlock 

 irregularly and in subordinate amount with the quartz. Apatite, 

 a colorless amphibole, associated with serpentine, biotite, rutile and 

 pyrite, comprise the accessory- minerals. It was hoped that such a 

 layer as this, cushioned more or less between micaceous layers, 

 would show some indication of secondary enlargement of the orig- 

 inal sand grains : it was found, however, that intense recrystalliza- 

 tion had obliterated all trace of original texture in the rock. 



