﻿GEOLOGY 
  OF 
  SARATOGA 
  SPRINGS 
  AND 
  VICINITY 
  127 
  

  

  All 
  the 
  slides 
  contain 
  crystals 
  of 
  black, 
  opaque 
  material. 
  There 
  

   are 
  occasional 
  small 
  crystals 
  of 
  pyrite. 
  There 
  is 
  much 
  minute, 
  

   dustlike 
  material, 
  especially 
  in 
  the 
  glass, 
  which 
  may 
  be 
  magnetite, 
  

   though 
  it 
  wholly 
  lacks 
  metallic 
  luster, 
  perhaps 
  because 
  of 
  its 
  min- 
  

   uteness. 
  There 
  is 
  also 
  much 
  somewhat 
  coarser 
  material, 
  of 
  irreg- 
  

   ular 
  outline 
  which 
  we 
  should 
  like 
  to 
  identify 
  as 
  graphite. 
  The 
  

   chemical 
  analysis 
  indicates 
  a 
  large 
  content 
  of 
  carbon 
  in 
  some 
  form, 
  

   but 
  in 
  reflected 
  light 
  this 
  material 
  does 
  not 
  show 
  a 
  metallic 
  luster 
  

   such 
  as 
  graphite 
  possesses, 
  but 
  takes 
  on 
  an 
  even, 
  whitish 
  sheen 
  

   which 
  we 
  are 
  unable 
  to 
  compare 
  with 
  anything 
  we 
  have 
  ever 
  seen 
  

   in 
  thin 
  section. 
  It 
  seems 
  present 
  in 
  the 
  slides 
  in 
  about 
  the 
  proper 
  

   quantity 
  to 
  account 
  for 
  the 
  carbon 
  shown 
  by 
  the 
  analysis 
  and 
  may 
  

   be 
  graphitoid, 
  or 
  some 
  other 
  carbonaceous 
  residue, 
  instead 
  of 
  

   graphite. 
  

  

  All 
  the 
  slides 
  contain 
  much 
  calcite. 
  It 
  fills 
  the 
  amygdules, 
  it 
  

   occurs 
  in 
  irregular 
  patches 
  throughout 
  the 
  balls, 
  and 
  it 
  solidly 
  

   welds 
  up 
  the 
  numerous 
  cracks 
  which 
  run 
  everywhere 
  through 
  

   the 
  lava. 
  

  

  The 
  calcite 
  in 
  the 
  cracks 
  gives 
  clear 
  evidence 
  of 
  the 
  deformation 
  

   to 
  which 
  the 
  rock 
  has 
  been 
  subjected 
  since 
  it 
  solidified. 
  It 
  shows 
  

   everywhere 
  the 
  close-set, 
  multiple 
  twinning, 
  and 
  the 
  undulatory 
  

   extinction 
  produced 
  by 
  the 
  deforming 
  stresses. 
  

  

  At 
  the 
  borders 
  of 
  the 
  limestone 
  inclusions 
  in 
  the 
  balls 
  a 
  slight 
  

   chilling 
  effect 
  is 
  manifest, 
  and 
  a 
  narrow 
  zone 
  of 
  glass 
  containing 
  

   much 
  finely 
  divided, 
  black, 
  opaque 
  matter 
  has 
  developed. 
  A 
  slight 
  

   amount 
  of 
  corrosion 
  has 
  also 
  occurred, 
  small 
  fragments 
  of 
  the 
  

   limestone 
  appearing 
  separated 
  from 
  the 
  main 
  mass 
  and 
  in 
  all 
  

   stages 
  o'f 
  solution 
  in 
  the 
  lava, 
  the 
  resulting 
  product 
  being 
  a 
  clear, 
  

   light 
  green 
  glass. 
  Examples 
  of 
  partially 
  corroded 
  limestone 
  sur- 
  

   rounded 
  by 
  such 
  glass 
  are 
  shown, 
  together 
  with 
  others 
  which 
  

   suggest 
  the 
  utter 
  disappearance 
  of 
  the 
  limestone 
  fragments, 
  the 
  

   glass 
  indicating 
  their 
  original 
  presence. 
  The 
  limestone 
  has 
  also 
  

   been 
  recrystallized 
  by 
  the 
  action 
  of 
  the 
  lava, 
  the 
  border 
  of 
  the 
  

   inclusion 
  being 
  more 
  coarsely 
  crystalline 
  than 
  the 
  interior. 
  

  

  The 
  . 
  pitchstone 
  which 
  constitutes 
  the 
  intervening 
  material 
  is 
  

   black, 
  but 
  becomes 
  a 
  clear, 
  light 
  green 
  glass 
  in 
  thin 
  section. 
  It 
  is 
  

   perfectly 
  clear 
  and 
  unaltered, 
  a 
  matter 
  of 
  some 
  surprise 
  when 
  it 
  

   is 
  recalled 
  how 
  completely 
  the 
  olivines 
  are 
  altered. 
  Except 
  in 
  the 
  

   vicinity 
  of 
  limestone 
  inclusions, 
  it 
  has 
  been 
  sheared 
  and 
  shows 
  

   its 
  condition 
  of 
  strain 
  by 
  being 
  doubly 
  refracting. 
  It 
  is 
  locally 
  

  

  