﻿150 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Shape 
  of 
  the 
  ore 
  bodies 
  

  

  The 
  form 
  assumed 
  by 
  the 
  ore 
  bodies 
  is 
  not 
  always 
  apparent 
  

   from 
  the 
  field 
  evidence. 
  It 
  is 
  only 
  the 
  smaller 
  ones 
  as 
  a 
  rule 
  that 
  

   are 
  well 
  exposed 
  in 
  outcrop. 
  The 
  large 
  bodies 
  have 
  nowhere 
  been 
  

   uncovered 
  or 
  explored 
  sufficiently 
  to 
  afford 
  an 
  idea 
  as 
  to 
  their 
  

   precise 
  outlines. 
  The 
  smaller 
  bodies, 
  with 
  a 
  few 
  exceptions 
  found 
  

   at 
  Lake 
  Sanford, 
  occur 
  in 
  gabbro 
  which 
  generally 
  appears 
  in 
  

   dikes 
  cutting 
  the 
  anorthosite, 
  and 
  partake 
  of 
  the 
  usual 
  tabular 
  

   form 
  with 
  the 
  longer 
  axis 
  parallel 
  to 
  the 
  strike 
  of 
  the 
  dikes. 
  They 
  

   show 
  gradation 
  at 
  the 
  edges 
  into 
  the 
  normal 
  gabbro 
  and 
  their 
  

   materials 
  have 
  no 
  doubt 
  come 
  up 
  with 
  it 
  from 
  a 
  common 
  reser- 
  

   voir 
  below. 
  As 
  to 
  the 
  deposits 
  inclosed 
  by 
  the 
  anorthosite, 
  it 
  is 
  

   not 
  conclusive 
  whether 
  the 
  ores 
  have 
  separated 
  in 
  place 
  from 
  the 
  

   surrounding 
  rock, 
  or 
  whether 
  they 
  represent 
  later 
  concentrations 
  

   in 
  the 
  interior 
  that 
  have 
  been 
  intruded 
  into 
  the 
  anorthosite 
  after 
  

   its 
  partial 
  solidification. 
  In 
  the 
  former 
  case 
  we 
  should 
  expect 
  

   the 
  bodies 
  to 
  be 
  quite 
  irregular, 
  with 
  no 
  well 
  defined 
  walls, 
  and 
  

   to 
  shade 
  off 
  at 
  the 
  borders 
  with 
  a 
  gradual 
  increase 
  in 
  the 
  propor- 
  

   tions 
  of 
  gangue 
  material 
  or 
  rock. 
  From 
  the 
  evidence 
  at 
  hand, 
  

   the 
  large 
  bodies 
  like 
  the 
  Lake 
  Sanford 
  would 
  appear 
  to 
  be 
  allied 
  

   rather 
  to 
  that 
  type 
  than 
  to 
  the 
  dike 
  form. 
  

  

  Mineralogy 
  of 
  the 
  magnetites 
  

  

  The 
  titaniferous 
  ores 
  of 
  the 
  Adirondacks 
  are 
  essentially 
  aggre- 
  

   gates 
  of 
  magnetite 
  and 
  ilmenite. 
  The 
  richest 
  ores 
  contain 
  little 
  else 
  

   than 
  these 
  minerals 
  and 
  shoiv 
  on 
  analysis 
  60 
  per 
  cent 
  or 
  slightly 
  more 
  

   of 
  iron, 
  the 
  maximum 
  percentage 
  being 
  somewhat 
  below 
  that 
  of 
  

   the 
  high-grade 
  nontitaniferous 
  magnetites. 
  From 
  such 
  pure 
  aggre- 
  

   gates 
  there 
  may 
  be 
  traced 
  a 
  continuous 
  series 
  of 
  gradations, 
  by 
  the 
  

   entering 
  of 
  gangue 
  minerals 
  in 
  greater 
  and 
  greater 
  proportions, 
  to 
  

   the 
  limiting 
  wall 
  rocks 
  which 
  hold 
  only 
  subordinate 
  amounts 
  of 
  

   magnetite 
  and 
  ilmenite. 
  

  

  The 
  relations 
  of 
  the 
  two 
  iron 
  minerals 
  have 
  received, 
  hitherto, 
  

   little 
  attention. 
  The 
  presence 
  of 
  ilmenite 
  has 
  been 
  inferred 
  from 
  the 
  

   results 
  of 
  chemical 
  analyses; 
  its 
  identification 
  by 
  the 
  usual 
  optical 
  

   methods 
  of 
  petrography 
  is 
  difficult 
  owing 
  to 
  its 
  opacity 
  and 
  simi- 
  

   larity 
  of 
  appearance 
  to 
  the 
  magnetite 
  with 
  which 
  it 
  is 
  intimately 
  

   associated. 
  

  

  Ilmenite 
  is 
  not 
  uniform 
  in 
  its 
  composition 
  and 
  its 
  chemical 
  

   nature 
  has 
  been 
  the 
  source 
  of 
  considerable 
  perplexity 
  to 
  mineral- 
  

   ogists. 
  The 
  view 
  that 
  it 
  is 
  a 
  metatitanate 
  Fe 
  Ti0 
  3 
  has 
  the 
  support 
  

  

  