﻿GEOLOGY 
  OF 
  SARATOGA 
  SPRINGS 
  AND 
  VICINITY 
  2? 
  

  

  Hudson 
  cuts 
  through 
  this 
  mass, 
  some 
  quarrying 
  has 
  been 
  done 
  in 
  

   it 
  to 
  furnish 
  masonry 
  for 
  Spiers 
  dam, 
  and 
  hence 
  the 
  general 
  ex- 
  

   hibit 
  of 
  the 
  rock 
  along 
  the 
  river 
  is 
  the 
  best 
  to 
  be 
  found 
  within 
  the 
  

   quadrangles. 
  Up 
  the 
  hill 
  west 
  of 
  Corinth 
  is 
  the 
  southern 
  half 
  to 
  two- 
  

   thirds 
  of 
  another 
  mass 
  running 
  north 
  on 
  to 
  the 
  Luzerne 
  sheet 
  ; 
  and 
  

   the 
  third 
  area 
  runs 
  west 
  from 
  Lake 
  Desolation 
  and 
  Mt 
  Pleasant 
  

   and 
  its 
  western 
  extension 
  may 
  be 
  seen 
  on 
  the 
  map 
  of 
  the 
  Broadalbin 
  

   quadrangle. 
  1 
  It 
  should 
  be 
  clearly 
  understood 
  that 
  the 
  boundaries 
  

   between 
  the 
  syenite 
  and 
  the 
  Grenville, 
  as 
  drawn 
  on 
  the 
  maps, 
  are 
  

   of 
  the 
  most 
  vague 
  description. 
  A 
  multitude 
  of 
  dikes 
  run 
  out 
  from 
  

   the 
  syenite 
  into 
  the 
  Grenville 
  ; 
  the 
  syenite 
  is 
  full 
  of 
  inclusions 
  of 
  

   Grenville 
  and 
  the 
  whole 
  combination 
  has 
  been 
  much 
  deformed. 
  

   There 
  is 
  plenty 
  of 
  syenite 
  outside 
  the 
  areas 
  mapped 
  as 
  such 
  and 
  

   there 
  is 
  much 
  Grenville 
  within 
  the 
  areas 
  mapped 
  as 
  syenite. 
  The 
  

   best 
  that 
  can 
  be 
  done 
  on 
  maps 
  of 
  this 
  scale 
  is 
  to 
  endeavor 
  to 
  map 
  

   as 
  syenite, 
  areas 
  in 
  which 
  this 
  rock 
  constitutes 
  more 
  than 
  50 
  per 
  

   cent 
  of 
  the 
  whole, 
  and 
  as 
  Grenville 
  those 
  in 
  which 
  the 
  syenite 
  con- 
  

   stitutes 
  less 
  than 
  50 
  per 
  cent. 
  

  

  The 
  syenites 
  have 
  been 
  described 
  in 
  detail, 
  with 
  chemical 
  analyses 
  

   in 
  so 
  many 
  of 
  the 
  New 
  York 
  State 
  Museum 
  bulletins 
  that 
  it 
  seems 
  

   superfluous 
  to 
  repeat 
  the 
  discussion 
  here. 
  2 
  As 
  shown 
  on 
  the 
  quad- 
  

   rangle, 
  they 
  are 
  usually 
  greenish 
  gray 
  rocks, 
  sometimes 
  blotched 
  

   with 
  red 
  and 
  grading 
  into 
  varieties 
  richer 
  in 
  quartz 
  and 
  wholly 
  

   red. 
  The 
  rock 
  is 
  thoroughly 
  gneissoid. 
  The 
  most 
  interesting 
  thing 
  

   about 
  it 
  is 
  the 
  way 
  in 
  which 
  it 
  uniformly 
  runs 
  over 
  into 
  coarsely, 
  

   porphyritic 
  varieties 
  at 
  the 
  margins 
  and 
  in 
  the 
  dikes 
  of 
  syenite 
  in 
  

   the 
  Grenville. 
  The 
  porphyritic 
  crystals, 
  usually 
  called 
  augen. 
  are 
  

   often 
  large, 
  reaching 
  a 
  length 
  of 
  2 
  inches, 
  while 
  those 
  of 
  an 
  inch 
  

   in 
  length 
  are 
  very 
  common 
  ; 
  the 
  feldspar 
  of 
  these 
  augen 
  is 
  usually 
  

   red, 
  the 
  augen 
  are 
  aligned 
  parallel 
  to 
  the 
  foliation, 
  and 
  in 
  many 
  

   cases 
  are 
  partly 
  or 
  wholly 
  crushed 
  or 
  granulated. 
  In 
  the 
  body 
  of 
  

   the 
  rock, 
  mica 
  has 
  developed 
  in 
  quantity 
  and 
  the 
  resemblance 
  to 
  a 
  

   metamorphosed 
  conglomerate 
  is 
  strong. 
  The 
  rock 
  is 
  considerably 
  

   more 
  quartzose 
  and 
  acid 
  than 
  the 
  main 
  body 
  of 
  the 
  syenite. 
  

  

  In 
  the 
  description 
  of 
  the 
  Alexandria 
  syenite 
  of 
  the 
  Alexandria 
  

   quadrangle, 
  a 
  similar 
  porphyritic, 
  marginal 
  phase 
  of 
  the 
  rock 
  was 
  

   described, 
  but 
  some 
  doubt 
  was 
  expressed 
  as 
  to 
  whether 
  it 
  was 
  in 
  

  

  1 
  W. 
  J. 
  Miller, 
  map 
  accompanying 
  N. 
  Y. 
  State 
  Mus. 
  Bui. 
  153. 
  

   -Bui. 
  95, 
  p. 
  312-40; 
  Bui. 
  115, 
  p. 
  512-25; 
  Bui. 
  138, 
  p. 
  44-52; 
  Bui. 
  145, 
  p. 
  

   182-84; 
  Bui. 
  153, 
  p. 
  14-21. 
  

  

  