(;i:()L(>(;v oi' s\l^\^()(;A si'Rixc.s and \i(i\ir\' 19 



somewhat, cla}- shales alternating with sandy shales, and these with 

 ealcareous shales. These original variations are still discernible 

 in the schists as bands of varying character, whose chief differ- 

 ences from one another are in the relative proportions of- the three 

 common minerals, quartz, feldspar and mica, which compose them. 



Grenville amphibolite. There is not a great quantity of amphib- 

 olite in the Grenville of the Saratoga (juadrangle, and such as 

 there is occurs mingled with the other Grenville rocks in masses 

 of no great size. It occurs in two different ways. On the one 

 hand it forms comparatively thin bands, so interbedded with the 

 other (irenville rocks as to make it highly probal)le that it re])re- 

 sents a band of sediment, a probable original calcareous shale, 

 'iliese bands often appear to grade into the general schists which 

 are interbedded with them. ( )n the other hand it occurs in more 

 or less oval masses which, notwithstanding their small size, seem 

 to cut through the other Grenville rocks, instead of being inter- 

 bedded, and hence to represent igneous rocks of somewhat later 

 age instead of contemporary sediments. The former are com- 

 monly, though not always, heavier, denser and blacker rocks than 

 the latter. Amphi1)olites of both types occur abundantly in the 

 Adirondacks, but it is by no means always possible definitely to 

 determine to which type a given occurrence belongs, esi)ecially 

 when the masses are as small as on this quadrangle. 



Grenville quartzite. The chief belt of Grenville rocks other 

 than schists is an east-west belt about a mile in breadth of surface 

 outcrop, which crosses the Saratoga (juadrangle through Cireenfield 

 township from just west of Kings Station to Mt IMeasant. This 

 is not a belt of solid ([uartzite. but consists of numerous beds of 

 {|uartzite. interbanded with various schists and with thin l)eds of 

 crystalline limestone. 11ie central ])art of the l)elt, downfaulted 

 into the Kayaderosseras valley, is covered by younger rocks. 

 West of Mt Pleasant it is cut out by syenite. Though occurring in 

 thin bands elsewhere, the (irenville quartzite and limestone of the 

 quadrangle are practically confined to this belt. 



The (|uartzites present substantiall)' the same \arielies as are 

 common elsewhere in the Adirondacks. There are beds of coarselv 

 crystalline, glassy looking (juartz rocks, in which (|uarlz constitutes 

 from 70 to 90 per cent of the rock, and the. remainder is chieflv feld- 

 spar. The finer grained ([uartzites are usually less quartzose, though 

 with (|uartz always forming 50 per ceiU or more of tlie rock. The\- 

 are usually (juartz-feldspar or (|uartz-j)yi-()xene rocks. The latter 



