﻿Warren, 
  Allan 
  and 
  Conner 
  — 
  A 
  Titaniferous 
  Augite. 
  77 
  

  

  also 
  in 
  monochromatic 
  light, 
  no 
  great 
  accuracy 
  can 
  be 
  claimed 
  

   for 
  this 
  measurement, 
  and 
  it 
  was 
  deemed 
  sufficient 
  to 
  measure 
  

   it 
  in 
  white 
  light 
  alone, 
  taking 
  the 
  readings 
  from 
  the 
  middle 
  of 
  

   the 
  black 
  brush 
  passing 
  through 
  the 
  one 
  optic 
  axis 
  to 
  the 
  

   division 
  between 
  the 
  strong 
  red 
  and 
  blue 
  parts 
  of 
  the 
  other 
  

   brush, 
  this 
  division 
  being 
  fairly 
  well 
  marked 
  — 
  the 
  sharpest 
  

   thing 
  about 
  the 
  interference 
  figure 
  in 
  fact. 
  One 
  section 
  gave 
  

   2E= 
  58"5°, 
  the 
  other, 
  59*5°, 
  or 
  an 
  average 
  of 
  59°. 
  In 
  sections 
  

   near 
  the 
  optic 
  axis 
  A, 
  the 
  interference 
  color 
  as 
  seen 
  in 
  parallel 
  

   light 
  between 
  crossed 
  nicols 
  is 
  a 
  peculiar 
  dull, 
  deep 
  blue 
  or 
  

   bluish 
  gray 
  ; 
  in 
  those 
  almost 
  perpendicular 
  to 
  the 
  axis, 
  the 
  

   color 
  is 
  still 
  more 
  dull 
  and 
  has 
  a 
  gray 
  or 
  brownish 
  tint. 
  The 
  

   sections 
  nearly 
  normal 
  to 
  the 
  acute 
  bisectrix 
  have 
  also 
  a 
  pecu- 
  

   liar 
  dull 
  brownish- 
  or 
  purplish-gray 
  color. 
  These 
  interfer- 
  

   ence 
  colors 
  are, 
  as 
  a 
  matter 
  of 
  fact, 
  quite 
  characteristic 
  of 
  the 
  

   thin-slices 
  of 
  the 
  rocks 
  carrying 
  this 
  augite. 
  

  

  Two 
  of 
  the 
  indices 
  of 
  refraction 
  were 
  determined 
  by 
  the 
  

   immersion 
  method, 
  and 
  were 
  found 
  to 
  be, 
  for 
  sodium 
  light, 
  

   a 
  = 
  1*725, 
  7 
  = 
  1*746. 
  This 
  makes 
  the 
  double- 
  refraction 
  equal 
  

   to 
  0*021. 
  This 
  is 
  agreement 
  with 
  the 
  value 
  estimated 
  from 
  

   the 
  thin-slice, 
  which 
  was 
  about 
  0*020. 
  

  

  A 
  very 
  careful 
  separation 
  of 
  the 
  augite 
  from 
  the 
  minerals 
  

   accompanying 
  it 
  was 
  carried 
  out 
  by 
  means 
  of 
  the 
  barium- 
  

   mercuric-iodide 
  solution. 
  The 
  final 
  product, 
  examined 
  under 
  

   the 
  microscope, 
  showed 
  a 
  very 
  satisfactory 
  degree 
  of 
  purity, 
  

   there 
  being 
  very 
  little 
  attached 
  or 
  included 
  hornblende 
  or 
  biotite 
  

   present, 
  and 
  only 
  traces 
  of 
  other 
  incidental 
  impurities. 
  The 
  

   mineral 
  thus 
  prepared 
  was 
  analyzed 
  by 
  Mr. 
  M. 
  F. 
  Conner, 
  of 
  

   Ottawa, 
  with 
  the 
  following 
  results 
  : 
  — 
  

  

  

  Augite 
  from 
  

   Ice 
  River 
  Syenite, 
  B. 
  C. 
  

   Conner, 
  Analyst. 
  

   % 
  

  

  Eatio. 
  

  

  

  Augite' 
  from 
  a 
  

   Monchiqnite 
  dike, 
  

  

  Rio 
  de 
  Janeiro. 
  

   Hunter, 
  Analyst. 
  

  

  % 
  Ratio. 
  

  

  SiO 
  .. 
  

  

  

  41*80 
  

  

  0-697 
  

  

  

  44-55 
  

  

  0-742 
  

  

  A1A 
  - 
  

  

  

  9-30 
  

  

  •091 
  

  

  

  7-86 
  

  

  •077 
  

  

  Fe 
  o 
  n 
  . 
  

  

  

  5-44 
  

  

  •034 
  

  

  

  3-81 
  

  

  •024 
  

  

  FeO 
  .. 
  

  

  

  3-30 
  

  

  •046 
  

  

  

  4-53 
  

  

  •063 
  

  

  MgO__ 
  

  

  

  10*82 
  

  

  •238 
  

  

  

  12-71 
  

  

  •318 
  

  

  CaO 
  .. 
  

  

  

  22-89 
  

  

  •409 
  

  

  

  20-84 
  

  

  .372 
  

  

  H,0- 
  

  

  

  0-16 
  

  

  

  

  

  

  H 
  + 
  

  

  

  1-10 
  

  

  '060 
  

  

  

  

  

  TiQ,._ 
  

  

  

  4-84 
  

  

  •060 
  

  

  

  2-85 
  

  

  •035 
  

  

  MnO 
  

  

  

  o-io 
  

  

  •002 
  

  

  

  •38 
  

  

  •006 
  

  

  

  

  99-75 
  

  

  

  Na„ 
  

   K 
  2 
  

  

  1-29 
  

   •49 
  

  

  •021 
  

   •005 
  

  

  Sp. 
  Gr. 
  

  

  = 
  3*39 
  

  

  

  

  Sp. 
  i 
  

  

  99*31 
  

   Grr. 
  = 
  3'284 
  

  

  

  