﻿100 
  Thietieth 
  Repokt 
  o^r 
  the 
  State 
  Museum. 
  

  

  rational 
  formulas 
  for 
  labradorites 
  as 
  individuals 
  comprised 
  

   under 
  a 
  general 
  labradorite 
  formula 
  of 
  n 
  molecules 
  anorthite 
  

   combined 
  with 
  one 
  molecule 
  of 
  albite. 
  It 
  is 
  lield 
  by 
  Rammels- 
  

   berg, 
  that 
  this 
  general 
  formula 
  is 
  sustained 
  by 
  the 
  results 
  of 
  

   all 
  properly 
  performed 
  analyses 
  of 
  such 
  feldspars, 
  and 
  if 
  these 
  

   results 
  do 
  not 
  admit 
  of 
  being 
  represented 
  by 
  a 
  certain 
  ratio 
  

   between 
  molecules, 
  they 
  are 
  to 
  be 
  set 
  aside 
  as 
  uncertain. 
  It 
  is 
  

   difficult 
  to 
  understand 
  how 
  the 
  term 
  mixture 
  can 
  be 
  properly 
  

   applied 
  in 
  this 
  case, 
  and 
  in 
  what 
  way 
  such 
  mixtures 
  of 
  n 
  mole- 
  

   cules 
  of 
  anorthite 
  and 
  one 
  molecule 
  of 
  albite 
  differ 
  from 
  a 
  

   chemical 
  compound 
  between 
  anorthite 
  and 
  albite 
  in 
  these 
  pro- 
  

   portions. 
  If 
  there 
  is 
  a 
  difference, 
  then 
  the 
  forces 
  concerned 
  in 
  

   the 
  crystallization 
  of 
  isomorphous 
  substances, 
  must 
  operate 
  to 
  

   produce 
  a 
  mixture 
  in 
  definite 
  molecular 
  proportions 
  — 
  a 
  suppo- 
  

   sition 
  not 
  at 
  all 
  in 
  accordance 
  with 
  what 
  takes 
  place 
  in 
  the 
  

   crystallization 
  of 
  isomorphous 
  artificial 
  salts. 
  Moreover 
  this 
  

   doctrine 
  excludes 
  from 
  the 
  category 
  of 
  labradorites, 
  many 
  

   minerals 
  eminently 
  characterized 
  by 
  all 
  the 
  distinctive 
  pecu- 
  

   liarities 
  of 
  this 
  species. 
  Notably 
  is 
  this 
  the 
  case 
  in 
  regard 
  to 
  

   the 
  four 
  following 
  Canadian 
  labradorites 
  : 
  I. 
  A 
  bluish- 
  white 
  

   granular 
  homogeneous 
  translucent 
  variety 
  from 
  Rawdon. 
  II. 
  

   A 
  similar 
  rock 
  from 
  Chateau 
  Richer, 
  pale 
  bluish 
  or 
  greenish- 
  

   gray, 
  with 
  red 
  spots. 
  The 
  lustre 
  on 
  the 
  cleavage 
  surfaces 
  of 
  

   the 
  grains 
  is 
  vitreous, 
  but 
  elsewhere 
  waxy. 
  The 
  rock 
  contains 
  

   small 
  scattered 
  flakes 
  of 
  black 
  mica. 
  III. 
  A 
  bluish 
  opalescent 
  

   cleavable 
  feldspar 
  from 
  Morin. 
  IV. 
  Lavender-blue 
  cleavable 
  

   feldspar, 
  with 
  gray 
  opalescence. 
  * 
  

  

  

  i. 
  

  

  n. 
  

  

  HI. 
  

  

  IV. 
  

  

  Sp. 
  Gt. 
  

  

  2.69 
  

  

  2.68 
  

  

  2.684-2.695 
  

  

  2.697 
  

  

  Silica 
  

  

  54.45 
  

  

  55.80 
  

  

  54.20 
  

  

  54.70 
  

  

  Alumina 
  

  

  28.05 
  

  

  26.90 
  

  

  29.10 
  

  

  29.80 
  

  

  Ferric 
  Oxide 
  

  

  0.45 
  

  

  1.53 
  

  

  1.10 
  

  

  0.36 
  

  

  Lime 
  

  

  9.68 
  

  

  9.0L 
  

  

  11.25 
  

  

  11.42 
  

  

  Magnesia 
  

  

  

  0.27 
  

  

  0.15 
  

  

  Tr. 
  

  

  Potash 
  

  

  1.06 
  

  

  0.86 
  

  

  undet. 
  

  

  0.23 
  

  

  Soda 
  

  

  6.25 
  

  

  4.77 
  

  

  t< 
  

  

  2.44 
  

  

  Water 
  

  

  0.55 
  

  

  0.45 
  

  

  0.40 
  

  

  0.40 
  

  

  100.49 
  99.59 
  99.35 
  

  

  Hunt, 
  Geology 
  of 
  Canada, 
  1863, 
  Chap, 
  xvii, 
  p. 
  478. 
  

  

  