﻿CRYSTALLINE 
  ROCKS 
  OF 
  THE 
  WESTERN 
  ADIRONDACK 
  REGION 
  489 
  

  

  From 
  the 
  genetic 
  point 
  of 
  view 
  the 
  ore 
  presents 
  an 
  interesting 
  

   but 
  troublesome 
  problem. 
  The 
  basis 
  of 
  known 
  facts 
  is 
  so 
  meager 
  

   as 
  to 
  make 
  any 
  conclusion 
  very 
  hypothetical, 
  for 
  even 
  the 
  nature 
  

   of 
  the 
  country 
  rock 
  is 
  uncertain. 
  But 
  whether 
  this 
  rock 
  is 
  igne- 
  

   ous 
  or 
  a 
  very 
  intensely 
  metamorphosed 
  sediment, 
  it 
  seems 
  to 
  the 
  

   writer 
  that 
  we 
  are 
  forced 
  to 
  about 
  the 
  same 
  explanation 
  for 
  the 
  

   ore 
  body. 
  

  

  Assuming 
  the 
  rock 
  to 
  be 
  as 
  it 
  probably 
  is 
  igneous, 
  the 
  structure, 
  

   composition 
  and 
  mode 
  of 
  occurrence 
  of 
  the 
  pegmatite 
  are 
  opposed 
  

   to 
  the 
  idea 
  that 
  it 
  is 
  a 
  strictly 
  primary 
  igneous 
  segregation. 
  In- 
  

   stead 
  it 
  is 
  much 
  more 
  likely 
  to 
  have 
  resulted 
  from 
  the 
  action 
  of 
  

   hot 
  solutions, 
  aided 
  perhaps 
  by 
  vapors, 
  acting 
  during 
  the 
  cooling 
  

   of 
  the 
  rock. 
  

  

  If 
  on 
  the 
  other 
  hand 
  the 
  country 
  rock 
  is 
  of 
  sedimentary 
  origin, 
  

   it 
  has 
  undergone 
  such 
  intense 
  metamorphism 
  as 
  to 
  be 
  con- 
  

   verted 
  into 
  a 
  rock 
  having 
  all 
  the 
  structural 
  peculiarities 
  of 
  a 
  

   granite. 
  Even 
  if 
  such 
  a 
  complete 
  change 
  can 
  be 
  effected 
  with- 
  

   out 
  fusion, 
  it 
  can 
  hardly 
  result 
  without 
  the 
  production 
  of 
  much 
  

   heat 
  and 
  in 
  consequence 
  heated 
  solutions 
  would 
  play 
  an 
  active 
  

   part 
  in 
  the 
  process 
  of 
  crystallization. 
  

  

  It 
  is 
  to 
  these 
  solutions 
  that 
  we 
  must 
  look 
  for 
  the 
  formation 
  of 
  

   the 
  ore 
  deposits, 
  and 
  thus 
  we 
  are 
  led 
  to 
  accept 
  a 
  process 
  quite 
  

   similar 
  to 
  that 
  first 
  suggested. 
  In 
  either 
  case 
  the 
  ore 
  is 
  regarded 
  

   as 
  concentrated 
  by 
  hot 
  solutions 
  from 
  the 
  immediately 
  adjacent 
  

   rocks. 
  

  

  That 
  the 
  ore 
  was 
  formed 
  by 
  one 
  of 
  the 
  processes 
  mentioned 
  and 
  

   most 
  probably 
  by 
  the 
  first 
  seems 
  to 
  the 
  writer 
  a 
  natural 
  and 
  jus- 
  

   tifiable 
  inference 
  from 
  the 
  phenomena 
  presented 
  in 
  the 
  deposit, 
  

   though 
  with 
  the 
  scanty 
  data 
  at 
  hand 
  it 
  is 
  impossible 
  to 
  follow 
  

   the 
  process 
  in 
  detail 
  or 
  even 
  to 
  be 
  certain 
  of 
  its 
  truth 
  in 
  a 
  general 
  

   way. 
  

  

  It 
  is 
  interesting 
  to 
  note 
  that 
  with 
  this 
  as 
  with 
  the 
  other 
  mag- 
  

   netite 
  deposits 
  thus 
  far 
  seen 
  in 
  the 
  western 
  Adirondacks 
  there 
  is 
  

   nothing 
  to 
  suggest 
  its 
  origin 
  as 
  a 
  contact 
  deposit 
  where 
  gabbro 
  

   is 
  intruded 
  into 
  gneiss, 
  as 
  Prof. 
  Kemp 
  has 
  shown 
  to 
  be 
  prob- 
  

   able 
  in 
  the 
  case 
  of 
  the 
  large 
  bodies 
  of 
  magnetite 
  in 
  the 
  gneisses 
  

  

  