﻿Notes 
  upon 
  the 
  Lithology 
  of 
  the 
  Adieokdacks. 
  101 
  

  

  The 
  quantivalents 
  ratios 
  for 
  R? 
  : 
  R 
  YI 
  : 
  Si 
  IV 
  are 
  for 
  1, 
  1 
  : 
  3 
  : 
  6.6, 
  

   in 
  II, 
  0.9 
  : 
  3 
  : 
  6.9, 
  in 
  III, 
  — 
  : 
  3 
  : 
  6.2, 
  in 
  IV, 
  0.84 
  : 
  3 
  : 
  6.2. 
  It 
  

   will 
  be 
  seen 
  that 
  these 
  ratios 
  differ 
  from 
  the 
  ratio, 
  1:3:6, 
  

   which 
  is 
  the 
  mean 
  for 
  the 
  labradorite 
  species, 
  by 
  an 
  excess 
  in 
  

   the 
  silicium. 
  This 
  is 
  due, 
  probably, 
  to 
  the 
  same 
  excess 
  of 
  

   uncombined 
  silica 
  over 
  the 
  amount 
  needed 
  to 
  form 
  the 
  labra- 
  

   dorite, 
  as 
  we 
  have 
  previously 
  noticed 
  was 
  characteristic 
  of 
  the 
  

   Adirondack 
  norian 
  labradorites. 
  The 
  atomic 
  ratios 
  are 
  for 
  : 
  — 
  

  

  Na 
  : 
  Ca 
  Al 
  : 
  Si 
  

  

  I. 
  1 
  : 
  1.8 
  1 
  : 
  3.2 
  

  

  II. 
  1 
  : 
  2.3 
  1 
  : 
  3.5 
  

  

  III. 
  1 
  : 
  3.2 
  

  

  IV. 
  1 
  : 
  5.8 
  1 
  : 
  3.1 
  

  

  But 
  these 
  numbers 
  do 
  not 
  permit 
  a 
  structura 
  formula 
  made 
  

   up 
  of 
  n 
  molecules 
  of 
  anorthite 
  and 
  one 
  of 
  albite. 
  They 
  are, 
  

   however, 
  entirely 
  compatible 
  with 
  Hunt's 
  original 
  theorem, 
  

   which, 
  freed 
  from 
  the 
  misconceptions 
  that 
  have 
  since 
  impaired 
  

   its 
  value 
  and 
  significance 
  is 
  — 
  That 
  the 
  triclinic 
  feldspars, 
  of 
  

   which 
  albite 
  and 
  anorthite 
  are 
  the 
  representatives, 
  are 
  members 
  

   of 
  a 
  series, 
  whose 
  composition 
  and 
  densities 
  are 
  such 
  that 
  they 
  

   all 
  enter 
  into 
  the 
  same 
  general 
  formula 
  with 
  them, 
  and 
  have 
  

   the 
  same 
  equivalent 
  volume, 
  and 
  it 
  is 
  probable 
  that 
  many, 
  if 
  

   not 
  all 
  of 
  them, 
  are 
  but 
  variable 
  mixtures 
  of 
  albite 
  and 
  anorthite. 
  

  

  The 
  only 
  feldspar 
  in 
  the 
  series 
  collected, 
  which 
  differed 
  so 
  

   strikingly 
  in 
  its 
  characters 
  from 
  those 
  whose 
  analyses 
  are 
  given 
  

   as 
  to 
  demand 
  a 
  separate 
  quantitative 
  analysis, 
  was 
  that 
  forming 
  

   the 
  non-norite 
  rock 
  (a), 
  which 
  we 
  have 
  already 
  found 
  was 
  

   excluded 
  from 
  the 
  category 
  given 
  in 
  Part 
  II, 
  and 
  formed 
  as 
  a 
  

   base, 
  along 
  with 
  quartz, 
  a 
  red 
  granitic 
  rock. 
  Its 
  composition 
  is 
  

  

  Silica 
  76.18 
  

  

  A1 
  2 
  3 
  12.41 
  

  

  Fe 
  2 
  3 
  2.97 
  

  

  CaO 
  0.11 
  

  

  MgO 
  0.22 
  

  

  K 
  2 
  5.19 
  

  

  Na 
  2 
  3.23 
  

  

  100.31 
  

  

  