﻿GEOLOGY 
  OF 
  SARATOGA 
  SPRINGS 
  AND 
  VICINITY 
  IO, 
  

  

  somewhat, 
  clay 
  shales 
  alternating 
  with 
  sandy 
  shales, 
  and 
  these 
  with 
  

   calcareous 
  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 
  quadrangle, 
  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 
  Grenville 
  rocks 
  as 
  to 
  make 
  it 
  highly 
  probable 
  that 
  it 
  repre- 
  

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

   These 
  bands 
  often 
  appear 
  to 
  grade 
  into 
  the 
  general 
  schists 
  which 
  

   are 
  interbedded 
  with 
  them. 
  On 
  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. 
  Amphibolites 
  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, 
  especially 
  

   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 
  quadrangle 
  through 
  Greenfield 
  

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

   is 
  not 
  a 
  belt 
  of 
  solid 
  quartzite, 
  but 
  consists 
  of 
  numerous 
  beds 
  of 
  

   quartzite, 
  interbanded 
  with 
  various 
  schists 
  and 
  with 
  thin 
  beds 
  of 
  

   crystalline 
  limestone. 
  The 
  central 
  part 
  of 
  the 
  belt, 
  downfaulted 
  

   into 
  the 
  Kayaderosseras 
  valley, 
  is 
  covered 
  by 
  younger 
  rocks. 
  

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

   thin 
  bands 
  elsewhere, 
  the 
  Grenville 
  quartzite 
  and 
  limestone 
  of 
  the 
  

   quadrangle 
  are 
  practically 
  confined 
  to 
  this 
  belt. 
  

  

  The 
  quartzites 
  present 
  substantially 
  the 
  same 
  varieties 
  as 
  are 
  

   common 
  elsewhere 
  in 
  the 
  Adirondacks. 
  There 
  are 
  beds 
  of 
  coarsely 
  

   crystalline, 
  glassy 
  looking 
  quartz 
  rocks, 
  in 
  which 
  quartz 
  constitutes 
  

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

   spar. 
  The 
  finer 
  grained 
  quartzites 
  are 
  usually 
  less 
  quartzose, 
  though 
  

   with 
  quartz 
  always 
  forming 
  50 
  per 
  cent 
  or 
  more 
  of 
  the 
  rock. 
  They 
  

   are 
  usually 
  quartz-feldspar 
  or 
  quartz-pyroxene 
  rocks. 
  The 
  latter 
  

  

  