﻿OF 
  THE 
  DIAJIANTIFEROtTS 
  ROCK 
  OF 
  SOUTH 
  AFRICA. 
  415 
  

  

  bronzite, 
  as 
  the 
  following 
  analysis 
  will 
  show. 
  From 
  the 
  impossibility 
  

   of 
  separating 
  the 
  minerals 
  mixed 
  with 
  even 
  the 
  most 
  compact 
  

   specimens 
  that 
  could 
  be 
  selected, 
  the 
  analysis 
  of 
  such 
  specimens 
  was 
  

   followed 
  by 
  treatment 
  with 
  potash. 
  

  

  The 
  percentage 
  composition 
  was 
  as 
  follows 
  : 
  — 
  

  

  Oxygen 
  Ratios. 
  

  

  Silicic 
  acid 
  66-915 
  35-68 
  

  

  Alumina 
  0-970 
  

  

  Chromium 
  oxide 
  . 
  . 
  0-^51 
  

  

  Iron 
  protoxide 
  .... 
  7'778 
  1-72' 
  

  

  Magnesia 
  19-785 
  7-91 
  > 
  9-95 
  

  

  Lime 
  1-115 
  0-32 
  

  

  Water 
  not 
  determined 
  

  

  96-814 
  

  

  A 
  quantity 
  of 
  the 
  powdered 
  mineral 
  was 
  treated 
  with 
  an 
  excess 
  

   of 
  potash 
  during 
  three 
  hours 
  at 
  100° 
  C, 
  when 
  constituents 
  amounting 
  

   to 
  41-614 
  per 
  cent, 
  were 
  removed. 
  They 
  were: 
  — 
  

  

  Silicic 
  acid 
  34-566 
  

  

  Alumina 
  1-152 
  

  

  Magnesia* 
  1-724 
  

  

  Water 
  (calculated) 
  3-186 
  

  

  40-628 
  

  

  The 
  oxygen 
  ratios 
  of 
  the 
  insoluble 
  portion 
  indicate, 
  as 
  will 
  be 
  

   seen 
  below, 
  the 
  composition 
  of 
  a 
  bronzite 
  for 
  the 
  other 
  constituent 
  

   mineral 
  of 
  this 
  rock. 
  

  

  Oxygen 
  Ratios. 
  

  

  Silicic 
  acid 
  32-349 
  17-25 
  

  

  Iron 
  protoxide 
  .... 
  7*778 
  1'72 
  1 
  R 
  q 
  . 
  

   Magnesia 
  18-061 
  7-22 
  J 
  

  

  58-188 
  

  

  The 
  matrix 
  of 
  the 
  striated 
  mineral 
  was 
  then 
  examined 
  with 
  the 
  

   following 
  results 
  : 
  — 
  

  

  Silicic 
  acid 
  74-776 
  

  

  Alumina 
  0-411 
  

  

  Chromium 
  oxide 
  0-946 
  

  

  Iron 
  protoxide 
  6-964 
  

  

  Magnesia 
  7*221 
  

  

  Lime 
  0-609 
  

  

  Water 
  5-135 
  

  

  Lime 
  carbonate 
  3*173 
  

  

  99-235 
  

  

  * 
  The 
  insoluble 
  part 
  was 
  washed 
  out 
  with 
  dilute 
  acetic 
  acid 
  towards 
  the 
  end 
  

   of 
  the 
  process, 
  in 
  order 
  to 
  prevent 
  the 
  passage 
  of 
  fine 
  particles 
  through 
  the 
  filter. 
  

  

  