﻿ADIRONDACK 
  MAGNETIC 
  IRON 
  ORES 
  27 
  

  

  There 
  can 
  be 
  no 
  doubt 
  that 
  the 
  form 
  assumed 
  by 
  the 
  ore 
  bodies 
  

   is 
  conditioned 
  by 
  the 
  structures 
  of 
  the 
  inclosing 
  rocks. 
  When 
  the 
  

   latter 
  are 
  foliated 
  to 
  an 
  extent 
  that 
  permits 
  observations 
  of 
  dip 
  

   and 
  strike, 
  the 
  contours 
  follow 
  the 
  changes 
  closely, 
  even 
  the 
  sub- 
  

   ordinate 
  ones. 
  This 
  feature 
  is 
  least 
  apparent 
  in 
  the 
  gneisses 
  of 
  the 
  

   igneous 
  series, 
  the 
  structures 
  of 
  which 
  are 
  often 
  only 
  faintly 
  indi- 
  

   cated, 
  and 
  most 
  evident 
  in 
  the 
  banded 
  gneisses 
  and 
  schists 
  of 
  the 
  

   Grenville. 
  The 
  ores 
  consequently 
  must 
  have 
  been 
  deposited 
  

   before 
  the 
  great 
  regional 
  disturbances 
  took 
  place, 
  or 
  at 
  least 
  before 
  

   the 
  rocks 
  received 
  their 
  present 
  structural 
  arrangement. 
  They 
  

   have 
  passed 
  through 
  all 
  the 
  vicissitudes 
  of 
  squeezing, 
  folding 
  and 
  

   other 
  deformations 
  that 
  have 
  been 
  impressed 
  upon 
  their 
  walls. 
  

  

  In 
  their 
  original 
  condition 
  the 
  ore 
  bodies 
  were 
  probably 
  tabular 
  

   masses, 
  like 
  those 
  now 
  existing 
  in 
  the 
  regions 
  of 
  least 
  disturbance. 
  

   From 
  such 
  masses, 
  a 
  complete 
  sequence 
  may 
  be 
  traced 
  into 
  lenses, 
  

   shoots 
  and 
  the 
  more 
  complicated 
  structures 
  that 
  have 
  been 
  devel- 
  

   oped 
  by 
  operation 
  of 
  mechanical 
  processes. 
  

  

  Associated 
  rocks 
  

  

  There 
  is 
  no 
  constant 
  type 
  or 
  formation 
  that 
  is 
  characteristic 
  for 
  

   the 
  nontitaniferous 
  ores 
  as 
  a 
  whole. 
  The 
  wall 
  rocks 
  include 
  gneisses 
  

   of 
  granitic, 
  syenitic 
  and 
  dioritic 
  composition, 
  acid 
  pyritic, 
  gar- 
  

   netiferous 
  gneisses, 
  hornblende 
  and 
  biotite 
  schists, 
  amphibolites 
  

   and 
  occasionally 
  crystalline 
  limestones. 
  

  

  From 
  considerations 
  of 
  their 
  probable 
  origin, 
  they 
  may 
  be 
  

   divided 
  into 
  (i) 
  igneous 
  derivatives 
  and 
  those 
  closely 
  allied 
  to 
  the 
  

   characteristic 
  intrusive 
  masses 
  of 
  the 
  Adirondacks; 
  (2) 
  members 
  

   of 
  the 
  sedimentary 
  or 
  Grenville 
  group. 
  Nearly 
  all 
  of 
  the 
  magnetite- 
  

   bearing 
  rocks 
  may 
  be 
  referred 
  with 
  a 
  degree 
  of 
  certainty 
  to 
  the 
  one 
  

   or 
  the 
  other 
  of 
  the 
  two 
  classes. 
  For 
  a 
  few 
  occurrences, 
  however, 
  

   the 
  evidences 
  of 
  relationships 
  that 
  have 
  been 
  found 
  thus 
  far 
  are 
  too 
  

   obscure 
  to 
  admit 
  any 
  definite 
  conclusions, 
  though 
  it 
  is 
  probable 
  

   that 
  the 
  rocks 
  are 
  uniform 
  with 
  the 
  others, 
  rather 
  than 
  character- 
  

   istic 
  of 
  a 
  distinct 
  class. 
  

  

  1 
  Igneous 
  group. 
  The 
  more 
  acid 
  members 
  of 
  the 
  igneous 
  series 
  

   constitute 
  the 
  country 
  of 
  the 
  Clinton 
  county 
  mines, 
  all 
  of 
  which 
  

   occur 
  within 
  the 
  belt 
  of 
  alkali-feldspar 
  gneisses 
  known 
  as 
  the 
  Saranac 
  

   formation. 
  At 
  Lyon 
  Mountain, 
  the 
  country 
  consists 
  of 
  a 
  massive 
  

   reddish 
  variety 
  composed 
  of 
  microperthite, 
  oligoclase, 
  green 
  augite, 
  

   hornblende 
  and 
  magnetite 
  with 
  a 
  small 
  amount 
  of 
  quartz. 
  Mineral- 
  

   ogically 
  it 
  lies 
  on 
  the 
  border 
  between 
  the 
  syenite 
  and 
  granite 
  rock 
  

  

  