﻿ADIRONDACK 
  MAGNETIC 
  IRON 
  ORES 
  - 
  I49 
  

  

  differing 
  in 
  composition 
  but 
  of 
  the 
  same 
  genesis 
  as 
  the 
  anorthosite 
  

   and 
  gabbro. 
  The 
  magnetite 
  and 
  ilmenite 
  of 
  which 
  they 
  are 
  aggre- 
  

   gates 
  exist 
  in 
  the 
  country 
  rocks 
  as 
  accessory 
  constituents. 
  A 
  

   ■concentration 
  that 
  took 
  place 
  probably 
  during 
  the 
  cooling 
  of 
  the 
  

   magma 
  effected 
  the 
  segregation 
  of 
  the 
  heavy 
  minerals 
  into 
  com- 
  

   pact 
  masses 
  forming 
  ore 
  bodies 
  of 
  variable 
  size 
  and 
  richness. 
  This 
  

   view 
  of 
  the 
  relation 
  of 
  the 
  Adirondack 
  ores 
  has 
  been 
  clearly 
  brought 
  

   out 
  by 
  Professor 
  Kemp 
  1 
  in 
  the 
  following 
  terms: 
  

  

  In 
  the 
  preceding 
  pages 
  the 
  point 
  of 
  view 
  has 
  been 
  consistently 
  

   maintained 
  that 
  the 
  ore 
  bodies 
  are 
  integral 
  portions 
  of 
  the 
  igneous 
  

   rocks 
  in 
  which 
  they 
  occur 
  and 
  are 
  merely 
  local 
  enrichments 
  of 
  

   the 
  mass 
  with 
  unusual 
  amounts 
  of 
  one 
  of 
  its 
  normal 
  constituent 
  

   minerals. 
  This 
  has 
  not 
  been 
  done 
  with 
  the 
  purpose 
  of 
  advocating 
  

   one 
  conception 
  of 
  the 
  relations 
  of 
  the 
  ore 
  and 
  wall 
  rock 
  to 
  the 
  

   exclusion 
  of 
  others, 
  but 
  because 
  the 
  observed 
  phenomena 
  admit 
  

   of 
  no 
  other 
  reasonable 
  interpretation. 
  There 
  is 
  no 
  evidence 
  of 
  

   the 
  replacement 
  of 
  preexisting 
  material 
  by 
  an 
  entering 
  foreign 
  sub- 
  

   stance, 
  nor 
  of 
  faults 
  and 
  vein 
  formation, 
  nor 
  of 
  crushed 
  zones 
  

   different 
  from 
  the 
  neighboring 
  walls 
  ; 
  nor 
  are 
  the 
  ores 
  at 
  the 
  con- 
  

   tacts 
  of 
  intrusions 
  with 
  country 
  rock. 
  On 
  the 
  contrary, 
  the 
  masses 
  

   of 
  ore, 
  of 
  irregular 
  shape, 
  are 
  far 
  within 
  the 
  intrusions, 
  and 
  especi- 
  

   ally 
  in 
  the 
  gabbros 
  they 
  vary 
  from 
  rich 
  titaniferous 
  iron 
  oxide, 
  

   through 
  leaner 
  and 
  leaner 
  examples, 
  until 
  normal 
  gabbro 
  is 
  reached. 
  

   No 
  minerals 
  or 
  elements 
  occur 
  in 
  notable 
  amounts 
  in 
  the 
  ores 
  which 
  

   are 
  not 
  characteristic 
  components 
  of 
  the 
  wall 
  rock. 
  The 
  difference 
  

   between 
  ore 
  and 
  rock 
  is 
  one 
  of 
  degree 
  and 
  not 
  of 
  kind. 
  At 
  

   Calamity 
  brook 
  the 
  ore 
  itself 
  forms 
  a 
  series 
  of 
  dikes 
  in 
  country 
  

   rock 
  of 
  a 
  different 
  kind. 
  

  

  The 
  causes 
  acting 
  to 
  produce 
  such 
  a 
  concentration 
  or 
  magmatic 
  

   differentiation 
  are 
  little 
  understood. 
  Gravity, 
  convection 
  cur- 
  

   rents, 
  magnetism, 
  and 
  diffusion 
  consequent 
  upon 
  variation 
  in 
  the 
  

   rate 
  of 
  cooling 
  are 
  some 
  of 
  the 
  agencies 
  that 
  have 
  been 
  appealed 
  

   to 
  by 
  the 
  leading 
  investigators 
  to 
  account 
  for 
  the 
  accumulation 
  

   of 
  the 
  deposits. 
  

  

  It 
  is 
  of 
  interest 
  to 
  note 
  that 
  the 
  igneous 
  theory 
  of 
  derivation 
  

   for 
  these 
  ores 
  which 
  has 
  come 
  into 
  prominence 
  in 
  recent 
  years 
  

   and 
  is 
  now 
  generally 
  accepted 
  by 
  geologists 
  the 
  world 
  over, 
  was 
  

   foreshadowed 
  by 
  Professor 
  Emmons 
  in 
  his 
  report 
  on 
  the 
  Adiron- 
  

   dack 
  region 
  for 
  1842. 
  The 
  ore 
  occurrences 
  at 
  Lake 
  Sanford 
  were 
  

   designated 
  by 
  him 
  as 
  " 
  masses," 
  to 
  distinguish 
  them 
  from 
  the 
  

   " 
  veins 
  " 
  or 
  tabular 
  bodies 
  occurring 
  in 
  the 
  gneisses, 
  and 
  they 
  

   are 
  described 
  as 
  of 
  contemporaneous 
  origin 
  with 
  the 
  inclosing 
  

   rocks 
  which 
  he 
  recognized 
  to 
  be 
  igneous. 
  

  

  1 
  Titaniferous 
  Iron 
  Ores 
  of 
  the 
  Adirondaeks, 
  p. 
  417. 
  

  

  