﻿ADIRONDACK 
  MAGNETIC 
  IRON 
  ORES 
  91 
  

  

  General 
  geology 
  

  

  The 
  higher 
  Adirondack 
  ridges 
  do 
  not 
  extend 
  much 
  beyond 
  the 
  

   Clinton 
  county 
  line. 
  The 
  Ausable 
  in 
  its 
  course 
  from 
  the 
  east 
  and 
  

   west 
  branches 
  to 
  Lake 
  Champlain 
  marks 
  the 
  limit 
  between 
  the 
  

   region 
  of 
  main 
  uplift 
  and 
  the 
  bordering 
  foothills. 
  South 
  of 
  the 
  river 
  

   the 
  surface 
  rises 
  quickly 
  to 
  the 
  level 
  of 
  the 
  flanking 
  ridges 
  which 
  is 
  

   less 
  than 
  1500 
  feet, 
  and 
  thence 
  abruptly 
  with 
  frequent 
  rock 
  scarps 
  

   to 
  the 
  interior 
  prominences 
  which 
  increase 
  in 
  hight 
  toward 
  the 
  

   southwest 
  and 
  merge 
  into 
  the 
  central 
  dominating 
  range 
  of 
  Essex 
  

   county. 
  On 
  the 
  north 
  side, 
  a 
  terraced 
  sand 
  plain 
  intervenes 
  between 
  

   the 
  river 
  and 
  the 
  first 
  ridge 
  forming 
  the 
  valley 
  wall. 
  In 
  the 
  stretch 
  

   from 
  Ausable 
  Forks 
  to 
  Clintonville 
  it 
  is 
  from 
  1 
  to 
  2 
  miles 
  wide 
  but 
  

   contracts 
  below 
  the 
  latter 
  place 
  where 
  the 
  valley 
  becomes 
  very 
  

   narrow. 
  The 
  hight 
  of 
  the 
  ridge 
  on 
  which 
  the 
  mines 
  are 
  situated 
  

   for 
  the 
  most 
  part 
  averages 
  about 
  11 
  00 
  feet 
  or 
  500 
  feet 
  above 
  the 
  

   level 
  of 
  the 
  plain. 
  4 
  

  

  The 
  anorthosites 
  and 
  associated 
  gabbros 
  which 
  are 
  so 
  widely 
  

   developed 
  to 
  the 
  south 
  do 
  not 
  occur 
  in 
  force 
  across 
  the 
  Clinton 
  

   county 
  line. 
  They 
  compose, 
  however, 
  the 
  higher 
  prominences 
  

   within 
  a 
  short 
  distance 
  of 
  the 
  Ausable 
  and 
  in 
  the 
  vicinity 
  of 
  Keese- 
  

   ville, 
  east 
  of 
  Clintonville, 
  even 
  extend 
  somewhat 
  over 
  the 
  line 
  as 
  a 
  

   narrow 
  tongue 
  diminishing 
  in 
  width 
  toward 
  the 
  north. 
  They 
  have 
  

   no 
  bearing 
  upon 
  the 
  iron 
  ores 
  and 
  will 
  not 
  be 
  further 
  considered. 
  

  

  Gneiss 
  series. 
  The 
  area 
  surrounding 
  the 
  ore 
  bodies 
  is 
  underlain 
  

   chiefly 
  by 
  an 
  acid 
  augite 
  gneiss, 
  a 
  part 
  of 
  the 
  basal 
  gneiss 
  series 
  

   (Saranac 
  formation) 
  which 
  borders 
  the 
  northeastern 
  Adirondacks 
  

   and 
  shows 
  much 
  uniformity 
  of 
  character 
  throughout 
  the 
  area. 
  

   Bands 
  of 
  darker 
  gneiss 
  and 
  pyritous 
  schists 
  that 
  can 
  be 
  referred 
  

   to 
  the 
  sedimentary 
  or 
  Grenville 
  series 
  occur 
  rarely 
  and 
  in 
  limited 
  

   outcrops. 
  Of 
  recognizable 
  igneous 
  rocks 
  there 
  are 
  small 
  exposures 
  

   of 
  syenite, 
  gabbro 
  and 
  diabase, 
  all 
  intrusive 
  in 
  the 
  gneiss 
  and 
  thus 
  

   of 
  later 
  age. 
  

  

  The 
  gneiss 
  presents 
  some 
  variations 
  from 
  place 
  to 
  place, 
  but 
  the 
  

   differences 
  either 
  in 
  structure 
  or 
  composition 
  are 
  seldom 
  so 
  pro- 
  

   nounced 
  that 
  a 
  basis 
  for 
  a 
  classification 
  is 
  afforded. 
  The 
  extremes 
  

   are 
  connected, 
  moreover, 
  by 
  transition 
  phases 
  and 
  are 
  intimately 
  

   associated 
  in 
  their 
  field 
  occurrence. 
  

  

  In 
  its 
  composition, 
  feldspar, 
  augite 
  and 
  quartz 
  partake 
  most 
  

   largely. 
  The 
  feldspars 
  may 
  be 
  microperthite, 
  orthoclase 
  or 
  micro- 
  

   cline 
  among 
  the 
  alkaline 
  varieties 
  which 
  are 
  the 
  prevailing 
  ones 
  Or 
  an 
  

   acid 
  plagioclase. 
  Microperthite 
  and 
  orthoclase 
  are 
  commoner 
  than 
  

   the 
  other 
  varieties 
  and 
  their 
  reddish 
  color 
  gives 
  the 
  predominant 
  

  

  