﻿Fenner 
  — 
  Stability 
  Relations 
  of 
  Silica 
  Minerals. 
  369 
  

  

  Table 
  I. 
  

  

  Temperature 
  of 
  a-(3 
  Inversions 
  of 
  Cristobalite, 
  showing 
  effects 
  of 
  previous 
  

  

  heat-treatment. 
  

  

  Inversion 
  Keversion 
  

   Method 
  of 
  formation 
  of 
  the 
  temperature 
  temperature 
  

  

  cristobalite 
  on 
  heating 
  on 
  cooling 
  

  

  No. 
  108. 
  Made 
  by 
  heating 
  finely 
  ground 
  ) 
  (a) 
  272*1° 
  ' 
  9 
  ~ 
  9 
  . 
  Q 
  o 
  238*5° 
  

  

  purified 
  quartz 
  withNa 
  2 
  W0 
  4 
  at 
  1580° 
  j" 
  (b) 
  273*6° 
  ata 
  ° 
  

  

  (a) 
  274-5° 
  

  

  No. 
  111. 
  Same 
  as 
  above, 
  at 
  1570° 
  (b) 
  272*5° 
  274*6° 
  238*1° 
  

  

  (c) 
  276*9° 
  

  

  No. 
  158a. 
  Produced 
  by 
  heating 
  fine- 
  "] 
  

  

  grained 
  cristobalite 
  with 
  Na 
  2 
  W0 
  4 
  i 
  (a) 
  272*1° 
  979ft0 
  231*9° 
  9007° 
  

  

  over 
  blast-lamp. 
  Is 
  mixture 
  of 
  tiidy- 
  f 
  (b) 
  272*0° 
  AiA 
  U 
  233*5° 
  A6A 
  ' 
  

  

  mite 
  and 
  cristobalite 
  crystals 
  J 
  

  

  No. 
  179. 
  From 
  ground 
  quartz 
  heated 
  ) 
  

  

  in 
  Fletcher 
  furnace 
  about 
  40 
  min. 
  at 
  f- 
  268*2° 
  240*5° 
  

  

  1640°± 
  ) 
  

  

  No. 
  116a. 
  Made 
  by 
  devitrifying 
  Si0 
  2 
  { 
  0171.10 
  osa 
  q° 
  

  

  glass 
  without 
  flux 
  at 
  1600° 
  J 
  AiL 
  l 
  A6 
  ^ 
  6 
  

  

  No. 
  116b. 
  From 
  large 
  quartz 
  crystals 
  ) 
  (a) 
  264*8° 
  0M1 
  o 
  233*2° 
  OQQ 
  AO 
  

  

  without 
  flux 
  at 
  1600° 
  j 
  (b) 
  263*5° 
  Atni 
  233*7° 
  A66 
  '^ 
  

  

  N 
  ^L 
  t 
  irat?58^.fr.^r 
  ri 
  !}|ji| 
  261 
  ' 
  4 
  ° 
  ?? 
  232 
  ' 
  r 
  

  

  No. 
  168. 
  Made 
  by 
  heating 
  tridymite 
  ) 
  oaQ 
  Q0 
  noo 
  no 
  

  

  without 
  flux 
  at 
  1 
  580° 
  ± 
  f 
  Ab&S 
  2d8 
  ' 
  2 
  

  

  No. 
  160a. 
  From 
  finelv 
  ground 
  quartz 
  / 
  (a) 
  259*9° 
  0A1 
  Q0 
  231*5° 
  OQA 
  A0 
  

  

  without 
  flux 
  at 
  1580° 
  \ 
  (b) 
  262*6° 
  ^ 
  l 
  6 
  229*3° 
  ^ 
  dU 
  * 
  4 
  

  

  No. 
  134. 
  From 
  purified 
  quartz 
  without 
  ) 
  9 
  ~ 
  Q 
  Q0 
  oqo 
  QO 
  

  

  flux 
  at 
  melting-point 
  of 
  platinum... 
  j 
  ADy 
  y 
  A6 
  " 
  6 
  

  

  No. 
  125. 
  From 
  amorphous 
  precipitated 
  ) 
  o*q.s° 
  oon 
  -10 
  

  

  silica 
  without 
  flux 
  at 
  1450° 
  f 
  25y 
  5 
  ^ 
  91 
  

  

  No. 
  183. 
  From 
  devitrification 
  of 
  silica 
  Mi! 
  !«'.?- 
  9 
  .*. 
  q 
  o 
  S12S 
  9r 
  .oo 
  

  

  glass 
  at 
  1360° 
  ± 
  for 
  93 
  hours 
  f 
  ( 
  °> 
  |™. 
  J 
  c 
  256 
  9 
  21? 
  2 
  21i 
  8 
  

  

  No. 
  126. 
  From 
  ground 
  quartz 
  without 
  ) 
  , 
  Qft 
  „ 
  no 
  , 
  , 
  

  

  fluxatl510° 
  j" 
  x548 
  ° 
  234 
  " 
  5 
  

  

  No. 
  121. 
  From 
  ground 
  quartz 
  without 
  ) 
  o^ni° 
  nio 
  O0 
  

  

  flux 
  at 
  1470°..... 
  j 
  - 
  A40 
  ' 
  1 
  218 
  " 
  8 
  

  

  No. 
  133. 
  From 
  finely 
  ground 
  quartz 
  ) 
  9 
  o 
  9 
  .k= 
  9nQ 
  . 
  9 
  o 
  

  

  heated 
  66 
  hours 
  at 
  1300°-1400° 
  \ 
  A6A 
  ° 
  ^ 
  uy 
  ^ 
  

  

  No. 
  142. 
  From 
  amorphous 
  precipitated 
  ) 
  oqa.q° 
  O 
  ^ 
  n 
  o 
  

  

  silica 
  heated 
  70 
  hours 
  at 
  1100° 
  ± 
  \ 
  " 
  dU 
  y 
  4 
  ° 
  ' 
  * 
  

  

  No. 
  175. 
  From 
  amorphous 
  precipitated 
  ) 
  oo~ 
  1° 
  on- 
  10 
  

  

  silica 
  heated 
  69 
  hours 
  at 
  1030° 
  ± 
  J" 
  aa 
  ** 
  ' 
  l 
  2U0 
  " 
  - 
  1 
  

  

  No. 
  184. 
  From 
  ground 
  quartz 
  heated 
  ) 
  (a) 
  229*5° 
  99Q 
  . 
  QO 
  213*8° 
  01Q 
  Q0 
  

  

  without 
  flux 
  903^ 
  hours 
  at 
  1360° 
  ± 
  .. 
  j" 
  (b) 
  229*1° 
  ^ 
  y 
  6 
  212*9° 
  Ai6 
  6 
  

  

  No. 
  166a. 
  From 
  silica 
  glass 
  heated 
  68 
  ) 
  01Q 
  „ 
  o 
  1001° 
  

  

  hours 
  at 
  approximately 
  1025°-1075°. 
  \ 
  AiJ 
  ' 
  iJ 
  ° 
  i 
  

  

  