﻿536 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  gradual 
  easterly 
  slope 
  of 
  the 
  hills, 
  and 
  to 
  their 
  steep 
  westerly 
  

   fronts, 
  the 
  same 
  relation 
  noted 
  around 
  Lake 
  Champlain. 
  Ap- 
  

   parently 
  the 
  Hudson 
  in 
  this 
  part 
  of 
  its 
  course, 
  follows 
  along 
  a 
  

   fault 
  line 
  whose 
  western 
  half 
  has 
  dropped. 
  

  

  Series 
  1. 
  The 
  prevailing 
  gneisses 
  in 
  Chester 
  are 
  coarsely 
  lami- 
  

   nated, 
  biotitic 
  varieties, 
  with 
  feldspar 
  as 
  a 
  rule 
  in 
  considerable 
  

   excess 
  and 
  with 
  abundant 
  garnets. 
  They 
  exhibit 
  many 
  evi- 
  

   dences 
  of 
  mashing 
  and 
  the 
  . 
  micaceous 
  streaks 
  forcibly 
  suggest 
  

   slipping 
  surfaces. 
  More 
  basic 
  varieties 
  with 
  abundant, 
  or 
  it 
  may 
  

   be, 
  predominant 
  hornblende 
  have 
  been 
  noted 
  in 
  a 
  few 
  places, 
  and 
  

   they 
  seem 
  to 
  constitute 
  subordinate 
  streaks 
  in 
  the 
  gneiss. 
  

  

  At 
  a 
  point 
  about 
  midway 
  between 
  the 
  north 
  end 
  of 
  Loon 
  lake 
  

   and 
  the 
  Schroon 
  river, 
  a 
  stratum 
  of 
  dark 
  gray 
  quartz 
  about 
  20 
  

   feet 
  thick 
  was 
  found 
  interbedded 
  in 
  the 
  gneiss, 
  and 
  having 
  sharp 
  

   contacts 
  with 
  it. 
  Many 
  little 
  flecks 
  of 
  pyrites 
  are 
  distributed 
  

   through 
  the 
  bed, 
  and 
  some 
  mica 
  and 
  garnets. 
  We 
  regard 
  it 
  as 
  

   a 
  thoroughly 
  recrystallized 
  quartzite. 
  The 
  clastic 
  character 
  has 
  

   been 
  destroyed 
  and 
  the 
  rock 
  now 
  gives 
  the 
  impression 
  of 
  vein 
  

   quartz. 
  

  

  Pegmatite 
  dikes 
  have 
  been 
  noted 
  in 
  one 
  or 
  two 
  places, 
  and 
  in 
  

   one 
  instance 
  a 
  dike 
  was 
  the 
  basis 
  of 
  an 
  unsuccessful 
  mining 
  

   venture 
  for 
  mica. 
  The 
  dike 
  is 
  near 
  a 
  gabbro 
  intrusion 
  on 
  a 
  hill- 
  

   top 
  about 
  three 
  miles 
  south 
  and 
  a 
  little 
  east 
  of 
  Ohestertown. 
  

  

  Series 
  2. 
  The 
  crystalline 
  limestones 
  outcrop 
  at 
  two 
  points, 
  one 
  

   at 
  the 
  northern 
  end 
  of 
  Loon 
  lake, 
  just 
  east 
  of 
  the 
  outlet 
  and 
  one 
  

   at 
  the 
  extreme 
  northwest 
  corner 
  of 
  the 
  township 
  opposite 
  North 
  

   river. 
  The 
  former 
  is 
  charged 
  with 
  pyroxene, 
  graphite 
  and 
  

   quartz, 
  and 
  the 
  latter 
  is 
  very 
  thickly 
  set 
  with 
  pyroxene, 
  but 
  both 
  

   appear 
  to 
  be 
  interbedded 
  in 
  the 
  gneisses. 
  The 
  latter 
  will 
  be 
  

   again 
  referred 
  to 
  under 
  Minerva. 
  

  

  Series 
  3. 
  Three 
  exposures 
  of 
  gabbro 
  have 
  been 
  met 
  in 
  the 
  cen- 
  

   tral 
  part 
  of 
  the 
  town, 
  near 
  the 
  two 
  lakes, 
  Friends 
  and 
  Loon. 
  The 
  

   one 
  just 
  west 
  of_Friends 
  lake, 
  is 
  associated 
  with 
  pegmatites 
  con- 
  

   taining 
  tourmaline. 
  The 
  one 
  southwest 
  of 
  Loon 
  lake 
  in 
  a 
  coarse 
  

   variety, 
  with 
  lath-shaped 
  feldspars 
  which 
  have 
  the 
  pyroxenes 
  

   of 
  irregular 
  outline 
  packed 
  in 
  between 
  them, 
  after 
  the 
  manner 
  

  

  