﻿JV. 
  L. 
  Bowen 
  — 
  Sodium- 
  Potassium 
  Nepltelites. 
  129 
  

  

  the 
  strongest 
  additional 
  reasons 
  for 
  stating 
  the 
  composition 
  of 
  

   nephelite 
  in 
  terms 
  of 
  the 
  molecules 
  JS 
  r 
  aAlSi0 
  4 
  , 
  KAlSi0 
  4 
  , 
  

   CaAl 
  2 
  Si 
  2 
  8 
  and 
  NaAlSi 
  3 
  O 
  s 
  . 
  These 
  appear, 
  moreover, 
  to 
  be 
  

   entirely 
  adequate 
  for 
  the 
  purpose, 
  apart 
  from 
  the 
  small 
  iron 
  

   content. 
  In 
  the 
  following 
  are 
  tabulated 
  the 
  percentages 
  by 
  

   weight 
  of 
  the 
  above 
  four 
  constituents 
  in 
  some 
  typical 
  nephe- 
  

   lites. 
  For 
  various 
  reasons 
  the 
  sums 
  of 
  these 
  constituents 
  are 
  

   not 
  100, 
  an 
  important 
  one 
  being 
  that 
  H 
  2 
  seems 
  to 
  replace 
  the 
  

   alkaline 
  oxides 
  to 
  a 
  moderate 
  extent 
  in 
  some 
  nephelites. 
  

  

  

  I 
  

  

  II 
  

  

  III 
  

  

  IV 
  

  

  V 
  

  

  VI 
  

  

  VII 
  

  

  VIII 
  

  

  IX 
  

  

  Ne 
  

  

  . 
  65-0 
  

  

  63-0 
  

  

  56.0 
  

  

  70-0 
  

  

  68-0 
  

  

  64-5 
  

  

  73-5 
  

  

  70-0 
  

  

  9*5 
  

  

  Kp 
  

  

  13-0 
  

  

  12-0 
  

  

  32-0 
  

  

  19*0 
  

  

  19-0 
  

  

  18-5 
  

  

  130 
  

  

  12*0 
  

  

  89*0 
  

  

  An 
  

  

  1-5 
  

  

  15-0 
  

  

  12-0 
  

  

  o-o 
  

  

  2-5 
  

  

  4-0 
  

  

  2-0 
  

  

  4-0 
  

  

  1*5 
  

  

  Ab 
  

  

  _ 
  9-5 
  

  

  2-0 
  

  

  o-o 
  

  

  io-o 
  

  

  9'5 
  

  

  5*0 
  

  

  6*0 
  

  

  11 
  -o 
  

  

  o-o 
  

  

  I. 
  Nephelite 
  from 
  Wausau, 
  Wis. 
  Weidman, 
  Geology 
  of 
  

   North 
  Central 
  Wisconsin, 
  Wisconsin 
  Survey 
  Bull., 
  xvi, 
  1907, 
  

   p. 
  317. 
  Analysis 
  I. 
  

  

  II. 
  Same. 
  Analysis 
  II. 
  

  

  III. 
  "Pseudonephelite" 
  Zambonini, 
  Zs. 
  Kryst., 
  lii, 
  606, 
  

   ,1913. 
  

  

  IV. 
  Nephelite 
  from 
  Eikaholmen, 
  Norway. 
  Foote 
  and 
  

   Bradley, 
  this 
  Journal, 
  xxxi, 
  27, 
  1911. 
  

  

  V. 
  Nephelite 
  from 
  Mariupol. 
  Morozewicz, 
  Bull. 
  Acad. 
  

   Sciences 
  Cracovie, 
  958, 
  1907. 
  

  

  VI. 
  Nephelite 
  from 
  Coimbatore, 
  India. 
  Mem. 
  Geol. 
  Surv. 
  

   Ind., 
  xxx, 
  pt. 
  3, 
  187, 
  1901. 
  

  

  VII. 
  Nephelite 
  from 
  Kuusamo. 
  Hackman 
  after 
  Ramsay, 
  

   Bull, 
  de 
  la 
  Commis. 
  Geol. 
  de 
  Finlande 
  No. 
  1 
  1, 
  9, 
  1911. 
  

  

  VIII. 
  Nephelite 
  from 
  Monte 
  Ferru. 
  Washington 
  and 
  Mer- 
  

   win, 
  Jour. 
  Wash. 
  Acad. 
  Sci., 
  v, 
  391, 
  1915. 
  

  

  IX. 
  Kaliophilite 
  from 
  Vesuvius. 
  Zambonini, 
  Mineralogia 
  

   Vesuviana 
  Appendix, 
  p. 
  23. 
  

  

  Dependable 
  analyses 
  of 
  nephelite 
  are 
  apparently 
  not 
  very 
  

   numerous 
  and 
  no 
  very 
  definite 
  general 
  conclusions 
  can 
  be 
  

   drawn 
  from 
  them. 
  Nephelite 
  III 
  shows 
  no 
  albite, 
  i. 
  e. 
  has 
  no 
  

   excess 
  silica 
  above 
  the 
  orthosilicate 
  ratio, 
  and 
  II 
  has 
  very 
  

   little,* 
  showing 
  that 
  excess 
  silica 
  is 
  not 
  essential. 
  When 
  the 
  

   albite 
  is 
  high 
  the 
  anorthite 
  tends 
  to 
  be 
  low 
  (I, 
  IV, 
  V 
  and 
  

   VIII) 
  and 
  when 
  the 
  anorthite 
  is 
  high 
  the 
  albite 
  tends 
  to 
  be 
  

   low 
  (II 
  and 
  III). 
  The 
  suggestion 
  is 
  that 
  the 
  members 
  of 
  the 
  

   former 
  group 
  were 
  formed 
  from 
  solutions 
  containing 
  sodic 
  

  

  * 
  Some 
  of 
  the 
  albite 
  of 
  II 
  occurs 
  as 
  minute 
  inclusions. 
  Weidman, 
  Wis. 
  

   Survey 
  Bull. 
  XVI, 
  p. 
  318. 
  It 
  might 
  be 
  assumed, 
  therefore, 
  that 
  the 
  nephe- 
  

   lite 
  should 
  be 
  saturated 
  with 
  albite 
  and 
  that 
  the 
  analysis 
  is 
  faulty. 
  It 
  is 
  

   possible, 
  however, 
  to 
  imagine 
  conditions 
  under 
  which 
  saturation 
  would 
  not 
  

   occur 
  even 
  with 
  albite 
  inclusions. 
  

  

  