﻿CRYSTALLINE 
  ROCKS 
  OF 
  THE 
  WESTERN 
  ADIRONDACK 
  REGION 
  491 
  

  

  green 
  hornblende, 
  with 
  accessory 
  zircon, 
  magnetite, 
  etc. 
  Not 
  un- 
  

   commonly 
  a 
  grayish 
  green, 
  monoclinic 
  pyroxene 
  appears 
  with 
  or 
  

   instead 
  of 
  the 
  hornblende, 
  and 
  biotite 
  is 
  occasionally 
  present. 
  

   The 
  microperthite 
  rarely 
  gives 
  place 
  to 
  a 
  plagloclase 
  feldspar. 
  

   The 
  quartz 
  is 
  on 
  the 
  whole 
  the 
  most 
  variable 
  mineral 
  as 
  to 
  quan- 
  

   tity, 
  usually 
  being 
  present 
  in 
  abundance 
  but 
  sometimes 
  quite 
  in- 
  

   conspicuous. 
  Cataclastic 
  structure 
  is 
  notably 
  rare, 
  having 
  been 
  

   obliterated 
  if 
  ever 
  present 
  by 
  recrystallization. 
  

  

  Gneissic 
  rocks 
  differing 
  in 
  a 
  more 
  or 
  less 
  marked 
  degree 
  from 
  

   the 
  last 
  occur 
  on 
  a 
  small 
  scale, 
  and 
  in 
  some 
  cases 
  are 
  doubtless 
  

   peculiar 
  modifications 
  of 
  the 
  hornblende 
  gneiss, 
  while 
  in 
  others 
  

   they 
  must 
  be 
  regarded 
  as 
  quite 
  distinct. 
  Of 
  the 
  latter 
  class 
  is 
  a 
  

   very 
  dark 
  colored 
  rock 
  outcropping 
  on 
  the 
  recently 
  constructed 
  

   road 
  from 
  Fourth 
  lake 
  to 
  Mohican 
  lake 
  about 
  two 
  miles 
  west 
  of 
  

   the 
  latter. 
  This 
  rock 
  is 
  composed 
  of 
  strongly 
  pleochroic 
  hypers- 
  

   thene 
  and 
  basic 
  plagioclase 
  with 
  an 
  abundance 
  of 
  garnet. 
  In 
  

   mineralogical 
  composition 
  therefore 
  it 
  is 
  garnetiferous 
  norite, 
  but 
  

   as 
  its 
  structural 
  relations 
  are 
  unknown- 
  it 
  can 
  not 
  be 
  classed 
  as 
  

   an 
  igneous 
  rock, 
  being 
  more 
  probably 
  a 
  member 
  of 
  the 
  limestone 
  

   formation. 
  

  

  Another 
  gneiss 
  that 
  appears 
  to 
  be 
  totally 
  distinct 
  from 
  the 
  pre- 
  

   vailing 
  hornblende 
  gneiss 
  occurs 
  on 
  the 
  long 
  point 
  jutting 
  out 
  

   from 
  the 
  western 
  shore 
  of 
  Eaquette 
  lake. 
  This 
  is 
  a 
  rather 
  fine 
  

   grained 
  rock 
  made 
  up 
  of 
  thin 
  alternating 
  pink 
  and 
  green 
  bands. 
  

   Nothing 
  could 
  present 
  a 
  greater 
  contrast 
  to 
  the 
  massive, 
  uni- 
  

   form 
  gray 
  gneiss 
  and 
  it 
  is 
  such 
  a 
  contrast 
  as 
  seems 
  to 
  demand 
  the 
  

   recognition 
  of 
  the 
  two 
  rocks 
  as 
  entirely 
  different 
  formations. 
  

   Still 
  other 
  types 
  of 
  gneiss 
  appear, 
  but 
  those 
  only 
  need 
  be 
  de- 
  

   scribed 
  which 
  occur 
  in 
  connection 
  with 
  the 
  crystalline 
  limestone 
  

   which 
  has 
  been 
  found 
  to 
  have 
  a 
  considerable 
  development 
  in 
  this 
  

   region. 
  

  

  In 
  a 
  previous 
  report 
  the 
  writer 
  stated 
  that, 
  while 
  in 
  passing 
  

   from 
  the 
  large 
  limestone 
  belts 
  of 
  St 
  Lawrence 
  co. 
  toward 
  the 
  

   southeast 
  the 
  amount 
  of 
  limestone 
  decreased, 
  it 
  was 
  probable 
  

   that 
  scattered 
  areas 
  would 
  be 
  found 
  all 
  through 
  the 
  Adirondack 
  

   region. 
  This 
  is 
  borne 
  out 
  by 
  the 
  presence 
  of 
  several 
  such 
  areas 
  

  

  