﻿ADIRONDACK 
  MAGNETIC 
  IRON 
  ORES 
  9 
  

  

  2000 
  feet, 
  to 
  the 
  St 
  Lawrence. 
  The 
  valley 
  of 
  the 
  St 
  Lawrence 
  in 
  

   this 
  section 
  has 
  been 
  worn 
  down 
  through 
  the 
  Paleozoic 
  strata 
  

   exposing 
  the 
  underlying 
  crystallines 
  in 
  belts 
  that 
  extend 
  to 
  the 
  

   river 
  itself. 
  

  

  The 
  history 
  of 
  the 
  Adirondack 
  topography 
  is 
  very 
  involved. 
  

   The 
  mountains 
  were 
  upraised 
  and 
  folded 
  long 
  before 
  Potsdam 
  

   time, 
  while 
  they 
  have 
  been 
  since 
  subjected 
  to 
  long 
  cycles 
  of 
  erosion 
  

   and 
  to 
  renewed 
  uplifts. 
  The 
  whole 
  region 
  appears 
  to 
  have 
  been 
  

   planed 
  nearly 
  level 
  in 
  the 
  early 
  Cambric 
  period. 
  It 
  probably 
  par- 
  

   ticipated 
  in 
  the 
  general 
  Appalachian 
  upheaval 
  and 
  has 
  subse- 
  

   quently 
  undergone 
  more 
  or 
  less 
  movement. 
  Local 
  faults 
  have 
  mod- 
  

   ified 
  the 
  erosional 
  features, 
  giving 
  rise 
  to 
  abrupt 
  rock 
  scarps, 
  serrated 
  

   ridges 
  which 
  appear 
  to 
  be 
  due 
  to 
  block 
  tilting, 
  and 
  to 
  wild 
  passes 
  

   and 
  gorgelike 
  valleys. 
  The 
  numerous 
  belts 
  of 
  crystalline 
  limestone 
  

   that 
  are 
  interfolded 
  with 
  the 
  other 
  crystallines 
  have 
  also 
  influenced 
  

   the 
  development 
  of 
  relief 
  by 
  their 
  more 
  rapid 
  wear. 
  The 
  valleys 
  

   floored 
  by 
  the 
  limestone 
  always 
  have 
  a 
  rounded 
  open 
  character, 
  in 
  

   contrast 
  with 
  the 
  usual 
  narrow 
  steep 
  sided 
  valleys 
  found 
  in 
  the 
  

   gneiss. 
  

  

  The 
  Labrador 
  ice 
  sheet 
  invaded 
  the 
  Adirondacks 
  from 
  the 
  north- 
  

   east 
  and 
  north, 
  scoured 
  the 
  ridges 
  to 
  the 
  summits 
  and 
  removed 
  the 
  

   products 
  of 
  rock 
  weathering 
  that 
  must 
  have 
  accumulated 
  in 
  great 
  

   thickness 
  during 
  the 
  long 
  period 
  in 
  which 
  the 
  region 
  had 
  been 
  

   exposed 
  to 
  subaerial 
  decay. 
  Residual 
  sands 
  and 
  clays 
  from 
  the 
  

   decomposition 
  of 
  rocks 
  in 
  place 
  are 
  practically 
  absent. 
  In 
  turn 
  

   the 
  ice 
  spread 
  over 
  the 
  region 
  enormous 
  quantities 
  of. 
  transported 
  

   materials 
  — 
  boulders, 
  gravels, 
  sands 
  and 
  clays. 
  The 
  preglacial 
  val- 
  

   leys 
  are 
  often 
  buried 
  beneath 
  hundreds 
  of 
  feet 
  of 
  such 
  materials. 
  It 
  

   is 
  to 
  obstructions 
  of 
  this 
  kind 
  that 
  many 
  of 
  the 
  lakes, 
  which 
  afford 
  

   one 
  of 
  the 
  most 
  attractive 
  scenic 
  features 
  of 
  the 
  Adirondacks, 
  owe 
  

   their 
  existence. 
  

  

  The 
  mineral 
  deposits 
  constitute 
  one 
  of 
  the 
  main 
  industrial 
  

   resources 
  of 
  the 
  region. 
  They 
  are 
  perhaps 
  second 
  in 
  importance 
  

   only 
  to 
  the 
  forests, 
  as 
  measured 
  by 
  value 
  of 
  the 
  output. 
  In 
  

   addition 
  to 
  the 
  iron 
  ores, 
  there 
  are 
  workable 
  deposits 
  of 
  talc, 
  

   graphite, 
  garnet, 
  feldspar 
  and 
  pyrite 
  in 
  different 
  parts 
  of 
  the 
  region. 
  

   The 
  quarry 
  materials, 
  of 
  which 
  there 
  are 
  inexhaustible 
  supplies, 
  

   include 
  granite, 
  syenite, 
  anorthosite, 
  trap, 
  limestone 
  and 
  marble, 
  

   suitable 
  for 
  building, 
  construction 
  or 
  ornamental 
  purposes. 
  

  

  