﻿ADIRONDACK 
  MAGNETIC 
  IRON 
  ORES 
  45 
  

  

  undertaken 
  by 
  the 
  Oliver 
  Iron 
  Mining 
  Co., 
  for 
  the 
  purpose 
  of 
  

   establishing 
  a 
  basis 
  for 
  exploratory 
  operations 
  with 
  the 
  diamond 
  

   drill. 
  The 
  field 
  work 
  was 
  carried 
  on 
  during 
  the 
  summer 
  of 
  1906 
  

   under 
  charge 
  of 
  Mr 
  M. 
  H. 
  Newman, 
  who 
  has 
  afforded 
  the 
  writer 
  

   every 
  opportunity 
  to 
  keep 
  in 
  touch 
  with 
  its 
  progress 
  and 
  likewise 
  

   to 
  make 
  use 
  of 
  the 
  results. 
  The 
  district 
  is 
  extremely 
  complex 
  

   geologically 
  by 
  reason 
  of 
  the 
  great 
  variety 
  of 
  rock 
  formations 
  

   represented, 
  which 
  involve 
  practically 
  the 
  whole 
  series 
  of 
  Adiron- 
  

   dack 
  crystallines, 
  and 
  the 
  intricate 
  structural 
  relations 
  resulting 
  

   from 
  plication, 
  faulting 
  and 
  the 
  intrusion 
  of 
  igneous 
  masses. 
  

  

  The 
  formations 
  may 
  be 
  divided 
  in 
  a 
  general 
  way 
  into 
  the 
  Ham- 
  

   mond 
  ville 
  or 
  ore-bearing 
  gneiss, 
  which 
  is 
  a 
  quartz-plagioclase 
  

   gneiss 
  of 
  doubtful 
  relationships; 
  a 
  group 
  of 
  metamorphosed 
  sedi- 
  

   ments 
  including 
  crystalline 
  limestone 
  and 
  hornblendic 
  and 
  mica- 
  

   ceous 
  gneisses 
  and 
  schists, 
  and 
  an 
  igneous 
  series 
  composed 
  of 
  

   anorthosite, 
  gabbro, 
  diabase, 
  syenite 
  and 
  granite. 
  This 
  is 
  essen- 
  

   tially 
  the 
  classification 
  proposed 
  by 
  Dr 
  Ogilvie 
  except 
  that 
  the 
  

   Hammondville 
  type 
  of 
  gneiss 
  is 
  considered 
  by 
  her 
  to 
  be 
  eruptive 
  

   and 
  is 
  mapped 
  with 
  the 
  granites. 
  

  

  Hammondville 
  gneiss. 
  The 
  rock 
  inclosing 
  the 
  deposits 
  is 
  dis- 
  

   tinguished 
  by 
  a 
  finely 
  granular 
  cataclastic 
  texture 
  and 
  almost 
  

   entire 
  absence 
  of 
  dark 
  minerals 
  except 
  magnetite. 
  It 
  has 
  a 
  homo- 
  

   geneous 
  character 
  for 
  the 
  most 
  part, 
  in 
  contrast 
  with 
  the 
  recog- 
  

   nizable 
  members 
  of 
  the 
  sedimentary 
  gneisses 
  which 
  vary 
  greatly 
  

   from 
  place 
  to 
  place. 
  Of 
  the 
  igneous 
  rocks 
  exposed 
  in 
  the 
  district, 
  

   it 
  most 
  closely 
  resembles 
  the 
  granite, 
  but 
  differs 
  in 
  some 
  particu- 
  

   lars 
  of 
  mineral 
  composition 
  and 
  in 
  the 
  more 
  intense 
  crushing 
  

   effects 
  which 
  it 
  exhibits. 
  

  

  Mineralogically 
  it 
  consists 
  almost 
  wholly 
  of 
  plagioclase 
  feldspar 
  

   and 
  quartz. 
  The 
  ferromagnesian 
  constituents 
  are 
  limited 
  to 
  

   occasional 
  shreds 
  of 
  biotite 
  and 
  a 
  little 
  green 
  hornblende, 
  forming 
  

   an 
  inconsiderable 
  proportion 
  of 
  the 
  mass. 
  Magnetite 
  is 
  fairly 
  

   abundant, 
  in 
  many 
  specimens 
  richly 
  so. 
  Apatite, 
  titanite 
  and 
  

   zircon 
  are 
  the 
  remaining 
  components. 
  

  

  The 
  rock 
  has 
  uniformly 
  a 
  grayish 
  color 
  on 
  unweathered 
  surfaces, 
  

   changing 
  to 
  brown 
  in 
  exposures, 
  with 
  sometimes 
  a 
  reddish 
  stain 
  

   from 
  a 
  little 
  included 
  pyrite. 
  In 
  the 
  finely 
  crushed 
  phases 
  it 
  looks 
  

   much 
  like 
  a 
  feldspathic 
  quart 
  zite. 
  In 
  the 
  percentage 
  of 
  silica 
  

   present 
  it 
  corresponds 
  to 
  an 
  acid 
  granite 
  with 
  an 
  indicated 
  content 
  

   of 
  70 
  per 
  cent 
  or 
  more, 
  but 
  it 
  differs 
  from 
  usual 
  granites 
  in 
  the 
  pre- 
  

   dominance 
  of 
  the 
  soda 
  feldspar, 
  the 
  potash 
  varieties 
  being 
  practi- 
  

   cally 
  absent. 
  The 
  magnesia 
  and 
  iron 
  are 
  below 
  the 
  average 
  for 
  

  

  