﻿ADIRONDACK 
  MAGNETIC 
  IRON 
  ORES 
  3 
  1 
  

  

  long 
  as 
  the 
  nature 
  of 
  the 
  rocks 
  themselves 
  remained 
  doubtful, 
  the 
  

   problem 
  might 
  be 
  viewed 
  obviously 
  from 
  several 
  standpoints. 
  

  

  The 
  sedimentary 
  theory 
  of 
  origin 
  has 
  been 
  held 
  in 
  most 
  favor 
  

   perhaps 
  by 
  geologists. 
  The 
  condition 
  precedent 
  to 
  its 
  application 
  

   is 
  that 
  the 
  inclosing 
  formations 
  are 
  themselves 
  of 
  sedimentary 
  

   derivation. 
  Different 
  modifications 
  of 
  the 
  general 
  theory 
  are 
  possi- 
  

   ble 
  : 
  the 
  deposits 
  may 
  be 
  considered 
  to 
  have 
  been 
  laid 
  down 
  in 
  the 
  

   form 
  of 
  magnetite, 
  in 
  which 
  case 
  they 
  represent 
  original 
  surface 
  

   concentrations 
  such 
  as 
  the 
  magnetite 
  sands 
  that 
  are 
  found 
  along 
  

   the 
  shores 
  of 
  lakes 
  and 
  streams; 
  they 
  may 
  have 
  been 
  originally 
  

   limonite 
  or 
  carbonate 
  ores 
  deposited 
  from 
  solution 
  and 
  subse- 
  

   quently 
  changed 
  under 
  the 
  influence 
  of 
  the 
  metamorphism 
  that 
  

   has 
  affected 
  the 
  wall 
  rocks. 
  The 
  apparent 
  conformity 
  between 
  the 
  

   deposits 
  and 
  the 
  foliation 
  of 
  the 
  gneisses, 
  their 
  lineal 
  development 
  

   and 
  persistence 
  for 
  Jong 
  distances 
  on 
  the 
  strike 
  are 
  supporting 
  

   arguments 
  for 
  the 
  sedimentary 
  theory. 
  

  

  In 
  a 
  previous 
  paper 
  on 
  the 
  Mineville 
  deposits, 
  1 
  Professor 
  Kemp 
  

   gave 
  the 
  first 
  detailed 
  account 
  of 
  the 
  geological 
  surroundings 
  of 
  the 
  

   magnetites. 
  As 
  a 
  result 
  of 
  his 
  investigations, 
  he 
  was 
  led 
  to 
  ques- 
  

   tion 
  the 
  applicability 
  of 
  the 
  sedimentary 
  theory 
  to 
  the 
  ores 
  of 
  that 
  

   district. 
  The 
  existence 
  of 
  igneous 
  masses 
  in 
  the 
  vicinity 
  and 
  the 
  

   evidences 
  of 
  their 
  agency 
  in 
  the 
  formation 
  of 
  many 
  of 
  the 
  accom- 
  

   panying 
  minerals 
  were 
  remarked 
  and 
  adduced 
  in 
  support 
  of 
  the 
  

   view 
  that 
  the 
  ores 
  have 
  been 
  introduced 
  by 
  processes 
  connected 
  

   with 
  the 
  intrusion 
  of 
  those 
  rocks, 
  more 
  particularly 
  the 
  gabbro 
  of 
  

   Barton 
  hill. 
  In 
  the 
  present 
  contribution 
  it 
  has 
  been 
  possible 
  to 
  

   clear 
  up 
  some 
  doubtful 
  points 
  relating 
  to 
  the 
  geology 
  of 
  the 
  dis- 
  

   trict, 
  with 
  the 
  result 
  that 
  a 
  more 
  immediate 
  source 
  of 
  the 
  iron 
  

   minerals 
  in 
  the 
  augite 
  syenite 
  is 
  indicated. 
  

  

  For 
  the 
  occurrences 
  in 
  the 
  midst 
  of 
  intrusive 
  rocks, 
  which 
  have 
  

   been 
  found 
  to 
  be 
  the 
  prevailing 
  type 
  in 
  the 
  eastern 
  Adirondacks, 
  

   there 
  would 
  seem 
  to 
  be 
  no 
  escape 
  from 
  the 
  conclusion 
  that 
  the 
  ores 
  

   have 
  formed 
  by 
  igneous 
  action. 
  They 
  are 
  related 
  to 
  the 
  wall 
  

   rocks 
  just 
  as 
  the 
  titaniferous 
  ores 
  are 
  related 
  to 
  the 
  gabbros 
  and 
  

   anorthosites. 
  

  

  The 
  processes 
  which 
  led 
  to 
  the 
  accumulation 
  of 
  these 
  deposits 
  

   may 
  have 
  varied 
  in 
  some 
  degree 
  in 
  the 
  different 
  localities. 
  Mag- 
  

   matic 
  differentiation 
  has 
  been, 
  no 
  doubt, 
  a 
  prominent 
  factor 
  in 
  the 
  

   early 
  stages 
  of 
  their 
  formation 
  and 
  perhaps 
  is 
  competent 
  to 
  explain 
  

   the 
  whole 
  course 
  of 
  their 
  development. 
  Yet 
  there 
  is 
  reason 
  for 
  

   believing 
  that 
  other 
  agencies 
  were 
  active 
  in 
  producing 
  the 
  final 
  

  

  1 
  Geology 
  of 
  the 
  Magnetites 
  near 
  Port 
  Henry, 
  N. 
  Y. 
  Am. 
  Inst. 
  Min. 
  Eng. 
  

   Trans, 
  v. 
  27. 
  1898. 
  

  

  