﻿6 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  magnetites, 
  (2) 
  titaniferous 
  magnetites, 
  and 
  (3) 
  hematites. 
  Of 
  

   the 
  three 
  classes 
  the 
  nontitaniferous 
  magnetites 
  are 
  the 
  character- 
  

   istic 
  product 
  of 
  the 
  region 
  and 
  have 
  afforded 
  by 
  far 
  the 
  greater 
  

   part 
  of 
  the 
  output. 
  

  

  The 
  occurrence 
  of 
  limonite 
  deserves 
  some 
  notice, 
  perhaps, 
  

   though 
  "it 
  can 
  hardly 
  be 
  considered 
  as 
  an 
  available 
  resource 
  at 
  the 
  

   present 
  time. 
  It 
  is 
  limited 
  to 
  surficial 
  accumulations 
  of 
  impure 
  

   bog 
  ore 
  doubtless 
  derived 
  from 
  solution 
  by 
  ground 
  water 
  of 
  the 
  iron 
  

   minerals 
  that 
  accompany 
  the 
  crystalline 
  rocks. 
  The 
  ore 
  is 
  only 
  

   occasionally 
  found 
  in 
  deposits 
  of 
  any 
  size 
  and 
  is 
  then 
  usually 
  too 
  

   lean 
  to 
  be 
  marketable. 
  It 
  has 
  been 
  exploited 
  on 
  a 
  small 
  scale 
  at 
  

   times 
  when 
  conditions 
  were 
  specially 
  favorable. 
  

  

  The 
  two 
  kinds 
  of 
  magnetites 
  mentioned 
  form 
  the 
  basis 
  of 
  the 
  

   present 
  report. 
  They 
  are 
  quite 
  distinct 
  in 
  respect 
  to 
  commercial 
  

   considerations, 
  as 
  well 
  as 
  in 
  the 
  particulars 
  of 
  their 
  geological 
  

   associations 
  and 
  local 
  distribution, 
  wherefore 
  it 
  has 
  been 
  thought 
  

   advisable 
  for 
  purposes 
  of 
  description 
  to 
  place 
  them 
  in 
  separate 
  

   divisions. 
  

  

  The 
  hematite 
  ores 
  are 
  practically 
  confined 
  to 
  a 
  single 
  district 
  

   on 
  the 
  west 
  side 
  of 
  the 
  Adirondacks. 
  They 
  have 
  been 
  mined 
  for 
  

   over 
  50 
  years 
  and 
  still 
  supply 
  a 
  considerable 
  output. 
  They 
  occur 
  

   within 
  metamorphosed 
  Precambric 
  sediments, 
  mainly 
  quart 
  zose 
  

   schists 
  and 
  limestones, 
  where 
  they 
  have 
  been 
  formed 
  by 
  a 
  process 
  

   of 
  chemical 
  replacement. 
  Their 
  detailed 
  description 
  is 
  reserved 
  

   for 
  a 
  future 
  paper. 
  x\n 
  isolated 
  deposit 
  of 
  hematite, 
  the 
  only 
  

   one 
  that 
  has 
  been 
  worked 
  outside 
  of 
  the 
  western 
  district, 
  is 
  found 
  

   near 
  Fort 
  Ticonderoga, 
  on 
  Lake 
  Champlain, 
  the 
  particulars 
  of 
  

   which 
  are 
  given 
  on 
  a 
  subsequent 
  page 
  of 
  the 
  present 
  report. 
  

  

  The 
  magnetite 
  deposits 
  of 
  the 
  Adirondacks 
  have 
  furnished 
  alto- 
  

   gether 
  not 
  less 
  than 
  35,000,000 
  tons 
  of 
  commercial 
  ore, 
  an 
  output 
  

   that 
  ranks 
  them 
  among 
  the 
  more 
  important 
  sources 
  of 
  this 
  class 
  

   of 
  ores 
  in 
  the 
  country. 
  They 
  have 
  been 
  exploited 
  almost 
  con- 
  

   tinuously 
  for 
  the 
  past 
  century, 
  the 
  earliest 
  operations 
  in 
  the 
  Cham- 
  

   plain 
  valley 
  dating 
  back 
  to 
  about 
  1800. 
  Though 
  some 
  deposits 
  

   have 
  been 
  practically 
  exhausted 
  by 
  past 
  operations, 
  these 
  are 
  

   mostly 
  the 
  smaller 
  ones, 
  many 
  of 
  which 
  would 
  not 
  repay 
  working 
  

   under 
  existing 
  circumstances. 
  The 
  larger 
  mines 
  now 
  operated 
  

   can 
  continue 
  along 
  present 
  lines 
  for 
  an 
  indefinite 
  period, 
  so 
  far 
  

   as 
  it 
  is 
  possible 
  to 
  judge 
  their 
  ore 
  reserves. 
  

  

  A 
  diminished 
  ore 
  supply, 
  in 
  fact, 
  is 
  of 
  less 
  concern 
  for 
  the 
  future 
  

   progress 
  of 
  mining, 
  than 
  the 
  possible 
  recurrence 
  of 
  a 
  period 
  of 
  

   inactive 
  demand 
  for 
  the 
  ores 
  such 
  as 
  has 
  been 
  felt 
  at 
  different 
  

   times 
  during 
  the 
  past. 
  It 
  is 
  believed, 
  however, 
  that 
  the 
  industry 
  

  

  