﻿ECONOMIC 
  GEOLOGY 
  217 
  

  

  beds 
  of 
  considerable 
  extent 
  and 
  thickne&s. 
  Accordingly 
  as 
  it 
  is 
  

   more 
  or 
  le&s 
  free 
  from 
  foreign 
  minerals 
  it 
  is 
  rich 
  or 
  lean, 
  varying 
  

   from 
  the 
  pure 
  magnetic 
  iron 
  ore 
  wMch 
  contains 
  72.4^ 
  of 
  iron 
  

   to 
  rock 
  containing 
  only 
  traces 
  of 
  iron 
  in 
  its 
  mineralogi- 
  

   cal 
  composition. 
  The 
  beds 
  of 
  ore 
  show 
  lamination 
  and 
  

   are 
  faulted, 
  folded 
  and 
  contorted 
  as 
  the 
  inclosing 
  strata 
  

   of 
  rock, 
  and 
  have 
  the 
  same 
  general 
  strike 
  and 
  dip 
  in 
  common 
  

   with 
  the 
  latter. 
  They 
  are 
  generally 
  of 
  irregular 
  form, 
  in 
  placea 
  

   widening 
  into 
  thick 
  deposits 
  or 
  lenticular 
  shaped 
  masses, 
  in 
  

   others 
  contracted 
  in 
  thin 
  sheets, 
  which 
  are 
  not 
  mined 
  profitatoly. 
  

   The 
  ore 
  is 
  found 
  in 
  some 
  cases 
  to 
  separate 
  into 
  thin 
  layers, 
  and 
  

   masses 
  ,of 
  rock 
  {' 
  horses 
  ') 
  are 
  met 
  with 
  entirely 
  suTrounded 
  by 
  

   the 
  ore. 
  The 
  phases 
  of 
  variation 
  are 
  almost 
  as 
  many 
  as 
  there 
  

   are 
  mines, 
  where 
  they 
  can 
  be 
  studied. 
  In 
  the 
  larger 
  and 
  older 
  

   mines 
  the 
  ore 
  has 
  been 
  followed 
  for 
  thousand's 
  of 
  feet 
  in 
  the 
  line 
  

   of 
  strike 
  or 
  on 
  the 
  course 
  of 
  the 
  ore, 
  and 
  for 
  hundreds 
  of 
  feet 
  in 
  

   depth 
  (on 
  the 
  line 
  of 
  dip) 
  without 
  reaching 
  its 
  limits. 
  Owing 
  to 
  

   the 
  unprofitable 
  nature 
  of 
  working 
  such 
  thin 
  ore 
  beds, 
  they 
  are 
  

   often 
  not 
  followed 
  to 
  the 
  end, 
  and 
  the 
  real 
  extent 
  of 
  few 
  of 
  these 
  

   ore 
  deposits 
  is 
  known. 
  In 
  general, 
  it 
  may 
  be 
  stated 
  that 
  in 
  this 
  

   region 
  tlie 
  ore 
  beds 
  stand 
  nearly 
  on 
  edge 
  and 
  have 
  a 
  noritheast 
  

   and 
  southwest 
  strike 
  and 
  a 
  descent 
  or 
  dip 
  at 
  a 
  steep 
  angle 
  to 
  the 
  

   southeast. 
  In 
  consequence 
  of 
  their 
  highly 
  inclined 
  posi'tion 
  and 
  

   their 
  irregular 
  shape 
  these 
  ore 
  bodies 
  are 
  called 
  ^ 
  veins,' 
  less 
  fre- 
  

   quently 
  ' 
  chimneys 
  ' 
  and 
  ' 
  shootis 
  ' 
  of 
  ore. 
  

  

  The 
  magnetic 
  iron 
  ore 
  has 
  not 
  been 
  found 
  distributed 
  uni- 
  

   formly 
  throughout 
  the 
  Highlands. 
  There 
  appear 
  to 
  be 
  certain 
  

   ore 
  ranges 
  or 
  belts 
  in 
  which 
  the 
  larger 
  and 
  more 
  productive 
  mines 
  

   are 
  opened. 
  There 
  are 
  mine 
  groups 
  also, 
  as 
  the 
  Sterling 
  Iron 
  and 
  

   Railway 
  Oomipany's 
  mines, 
  the 
  Greenwood 
  mines, 
  in 
  Orange 
  

   county; 
  the 
  Todd-Croft 
  and 
  Sunk 
  mines, 
  and 
  the 
  Oroton- 
  

   Brewster 
  ranges 
  in 
  Putnam 
  county. 
  The 
  boundaries 
  of 
  these 
  

   ore^bearing 
  belts 
  and 
  the 
  intermedialte 
  barren 
  territory 
  have 
  not 
  

   been 
  determined, 
  since 
  the 
  exploration 
  has 
  been 
  largely 
  made 
  by 
  

   individual 
  effort 
  and 
  without 
  any 
  general 
  plan 
  covering 
  the 
  

   whole 
  area. 
  

  

  Mines 
  have 
  been 
  opened 
  in 
  Orange, 
  Rockland, 
  Westchester 
  

  

  