﻿Composition 
  of 
  the 
  Trap 
  of 
  Ixocky 
  Hill, 
  N. 
  J. 
  283 
  

  

  In 
  this 
  feldspar 
  the 
  albite 
  molecule 
  is 
  to 
  the 
  anorthite 
  mole- 
  

   cule 
  as 
  1 
  : 
  1+ 
  or 
  the 
  feldspar 
  is 
  a 
  normal 
  labradorite, 
  which 
  

   agrees 
  well 
  with 
  the 
  optical 
  properties 
  as 
  found 
  in 
  quarry 
  ISTo. 
  2. 
  

  

  lY 
  gives 
  the 
  theoretical 
  percentage 
  composition 
  of 
  a 
  labra- 
  

   dorite 
  of 
  the 
  proportion 
  of 
  3 
  molecules 
  of 
  albite 
  to 
  4 
  molecules 
  

   of 
  anorthite". 
  

  

  II. 
  Gravity 
  <2-69. 
  Ratio 
  of 
  

   R 
  O 
  : 
  RO 
  : 
  RO, 
  : 
  SiO„ 
  

  

  140 
  : 
  119 
  : 
  219 
  : 
  1-037. 
  

  

  This 
  would 
  represent 
  a 
  feldspar 
  of 
  the 
  composition 
  of 
  albite 
  

   to 
  anorthite 
  in 
  the 
  proportion 
  of 
  5:2+ 
  and 
  would 
  be 
  that 
  of 
  an 
  

   oligoclase. 
  

  

  Y 
  represents 
  the 
  composition 
  and 
  gravity 
  of 
  an 
  oligoclase 
  

   of 
  the 
  proportion 
  of 
  3Ab 
  : 
  lAn.'' 
  

  

  Feldspars 
  frora 
  Quarry 
  Xo. 
  3. 
  

  

  

  

  

  I. 
  

  

  II 
  

  

  

  III. 
  

  

  

  lY. 
  

  

  

  

  Gravity 
  

  

  > 
  2-69. 
  

   Ratio. 
  

  

  Gravity 
  

  

  <2-69. 
  

   Ratio. 
  

  

  Gravity 
  < 
  2-60. 
  

   Ratio. 
  

  

  Gravity 
  

   2-577. 
  

  

  SiO,.... 
  

  

  

  

  66-84 
  

  

  i^no 
  

  

  71-68 
  

  

  1-195 
  

  

  66^28 
  1 
  

  

  •104 
  

  

  66-79 
  

  

  Al 
  

  

  

  17-98 
  

   2-60 
  

   4-02 
  

  

  •176 
  

   •016 
  

   •071 
  

  

  15-02 
  

  

  2-48 
  

   3^86 
  

  

  •147 
  

   •015 
  

  

  •068 
  

  

  16^79 
  

  

  1-60 
  

  

  •71 
  

  

  •164 
  

   •010 
  

   •012 
  

  

  19-36 
  

  

  FeO 
  - 
  

  

  

  •91 
  

  

  CaO-... 
  

  

  

  -80 
  

  

  M^O 
  . 
  . 
  

  

  

  •48 
  

  

  •012 
  

  

  •12 
  

  

  •003 
  

  

  •13 
  

  

  •003 
  

  

  •13 
  

  

  Na,03 
  -- 
  

  

  

  5-46 
  

  

  •088 
  

  

  5.52 
  

  

  •076 
  

  

  9-76 
  

  

  •057 
  

  

  7^34 
  

  

  k6 
  .. 
  

  

  

  1-72 
  

   •72 
  

  

  •018 
  

  

  1-37 
  

   •00 
  

  

  •014 
  

  

  5-31 
  

   •49 
  

  

  •056 
  

  

  4^95 
  

  

  IgnitiOD 
  

  

  

  

  

  

  99-82 
  

  

  100-05 
  

  

  101-07 
  

  

  100^28 
  

  

  I. 
  

  

  R,0 
  

  

  106 
  

  

  : 
  RO 
  : 
  

  

  : 
  83 
  : 
  

  

  R.O3 
  •• 
  

  

  192 
  : 
  

  

  SiO, 
  ) 
  

   1-110 
  \ 
  

  

  = 
  9 
  Ab 
  

  

  : 
  3-5 
  An 
  

  

  

  

  11. 
  

  

  R,0 
  

  

  90 
  

  

  : 
  RO 
  : 
  

  

  : 
  -71 
  : 
  

  

  162 
  : 
  

  

  SiO, 
  ) 
  

   1195 
  \ 
  

  

  = 
  5 
  Ab 
  

  

  : 
  2 
  Au. 
  

  

  

  

  III. 
  

  

  R,0 
  

  

  213 
  

  

  : 
  RO 
  : 
  

  

  : 
  15 
  : 
  

  

  174 
  : 
  

  

  SiO, 
  ) 
  

   1104 
  \ 
  

  

  = 
  6 
  0, 
  

  

  : 
  22 
  Ab 
  

  

  : 
  1 
  An. 
  

  

  

  

  K.O 
  

  

  Na,0 
  

  

  

  

  

  

  

  

  

  56 
  

  

  157 
  

  

  

  

  

  

  

  lY 
  is 
  the 
  composition 
  of 
  an 
  anorthoclase."* 
  In 
  the 
  analyses 
  

   of 
  the 
  feldspars 
  from 
  quarry 
  No. 
  3 
  it 
  was 
  impossible 
  to 
  get 
  

   good 
  samples, 
  from 
  the 
  fact 
  that 
  they 
  are 
  considerably 
  decom- 
  

   posed 
  and 
  stained 
  by 
  infiltration 
  of 
  iron 
  ; 
  in 
  addition 
  to 
  this 
  all 
  

   the 
  quartz 
  found 
  in 
  this 
  locality 
  will 
  be 
  included 
  in 
  II, 
  and 
  for 
  

   that 
  reason 
  the 
  percentage 
  of 
  Si02 
  here 
  runs 
  up 
  to 
  71. 
  While 
  

   the 
  above 
  analyses 
  cannot 
  strictly 
  be 
  taken 
  to 
  represent 
  the 
  

   composition 
  of 
  pure 
  feldspars, 
  they 
  will 
  represent, 
  however, 
  

   the 
  relation 
  of 
  K^O, 
  I^a^O 
  and 
  Cat) 
  in 
  the 
  feldspars 
  of 
  this 
  

   position 
  in 
  the 
  dike, 
  and 
  will 
  also 
  enable 
  us 
  to 
  make 
  a 
  com- 
  

   parison 
  with 
  the 
  feldspars 
  of 
  No. 
  2 
  crystallizing 
  earlier. 
  

  

  