﻿240 
  JOURNAL 
  OF 
  TH]e 
  WASHINGTON 
  ACADEMY 
  OP 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  10 
  

  

  Another 
  white 
  chlorite 
  of 
  related 
  composition 
  is 
  sheridanite, 
  de- 
  

   scribed 
  from 
  northern 
  Wyoming 
  by 
  J. 
  B. 
  Wolff 
  in 
  1912.^ 
  This 
  differs- 
  

   considerably 
  in 
  properties, 
  however, 
  being 
  a 
  translucent 
  greenish 
  

   gray 
  schistose 
  rock. 
  A 
  specimen 
  of 
  schistose 
  rock 
  from 
  Miles 
  City, 
  

   Montana, 
  has 
  recently 
  been 
  sent 
  in 
  to 
  the 
  U. 
  S. 
  Geological 
  Survey 
  for 
  

   identification, 
  and 
  Dr. 
  E. 
  S. 
  Larsen 
  has 
  found 
  it 
  to 
  agree 
  optically 
  

   with 
  sheridanite. 
  This 
  has 
  also 
  been 
  analyzed, 
  and 
  found 
  to 
  have 
  

   the 
  same 
  composition 
  as 
  the 
  original 
  sheridanite, 
  so 
  is 
  here 
  reported 
  as 
  a 
  

   new 
  occurrence 
  of 
  this 
  mineral. 
  In 
  the 
  analyses 
  extreme 
  care 
  was 
  

   taken 
  to 
  separate 
  the 
  aluminium 
  from 
  the 
  magnesium, 
  the 
  aluminium 
  

   hydroxide 
  being 
  reprecipitated 
  several 
  times. 
  The 
  results 
  of 
  the 
  new 
  

   analyses, 
  with 
  older 
  ones 
  for 
  comparison, 
  are 
  presented 
  in 
  table 
  1. 
  

  

  TABLE 
  1. 
  — 
  Analyses 
  of 
  White 
  Chlorites. 
  The 
  Asterisks 
  Indicate 
  New 
  Analyses 
  

  

  AND 
  Optical 
  Data. 
  The 
  Numbers 
  in 
  Parentheses 
  after 
  

  

  Analytical 
  Data 
  Are 
  Ratios 
  

  

  1* 
  2* 
  3 
  4* 
  5 
  6 
  

  

  SiOo 
  28.10(2) 
  36.70(6) 
  28.81(2) 
  27.78(2) 
  26.98(3) 
  24.40(2) 
  

  

  AI2O3 
  26.20(1) 
  10.38(1) 
  26.43(1) 
  24.30(1) 
  16.10(1) 
  22.77(1) 
  

  

  FezOs 
  1.66 
  1.22 
  0.24 
  1.43 
  0.22 
  0.45 
  

  

  FeO 
  none 
  trace 
  . 
  40 
  0.35 
  none 
  none 
  

  

  CaO 
  trace 
  . 
  86 
  none 
  trace 
  0.12 
  . 
  10 
  

  

  MnO 
  trace 
  trace 
  none 
  none 
  . 
  20 
  . 
  09 
  

  

  MGO 
  30.36(3) 
  36.44(9) 
  31.21(3) 
  32.71(3) 
  36.56(6) 
  32.70(4) 
  

  

  ^■O^ 
  If, 
  ■■■ 
  \ 
  0.28 
  0.30 
  

  

  NaoO 
  ... 
  ... 
  0.14 
  ... 
  I 
  

  

  HoO- 
  0.56 
  1.06 
  0.09 
  0.06 
  | 
  

  

  \ 
  19.91(7) 
  19.63(5) 
  

  

  H2O+ 
  14.00(3) 
  13.80(7) 
  12.62(3) 
  13.01(3) 
  J 
  

  

  Totals 
  100.88 
  100.46 
  100.29 
  99.64 
  100.37 
  100.44 
  

  

  Opt. 
  data 
  * 
  * 
  ... 
  * 
  * 
  

  

  a 
  1 
  . 
  562 
  1 
  . 
  555 
  1 
  . 
  580 
  1 
  . 
  ,576 
  1 
  . 
  570 
  

  

  |8 
  1.562 
  1.560 
  1.581 
  1.576 
  1.570 
  1.570 
  

  

  7 
  1 
  . 
  576 
  1 
  . 
  560 
  1 
  . 
  589 
  1 
  . 
  589 
  1 
  . 
  575 
  . 
  . 
  . 
  ■ 
  

  

  Sign 
  +_ 
  + 
  + 
  + 
  + 
  

  

  2E 
  0° 
  30° 
  35° 
  small 
  0° 
  0° 
  

  

  1. 
  White 
  chlorite 
  from 
  Brinton's 
  Quarry, 
  Pa. 
  Analysis 
  by 
  Shannon; 
  optical 
  data 
  de- 
  

   termined 
  on 
  an 
  exceptionally 
  clean 
  cut 
  crystal 
  and 
  kindly 
  furnished 
  by 
  Mr. 
  Gordon. 
  

  

  2. 
  White 
  chlorite 
  from 
  Nottingham, 
  Pa. 
  Analysis 
  by 
  Shannon 
  ; 
  optical 
  data 
  by 
  Wherry. 
  

  

  3. 
  Sheridanite, 
  northern 
  Wyoming. 
  Analysis 
  by 
  Wolff, 
  optical 
  data 
  by 
  H. 
  E- 
  Merwin. 
  

  

  4. 
  New 
  occurrence 
  of 
  sheridanite 
  (Wyoming?). 
  Analysis 
  by 
  Shannon; 
  optical 
  data 
  by 
  

   Larsen. 
  

  

  5. 
  Colerainite 
  matrix, 
  Quebec. 
  Analysis 
  by 
  Connor 
  quoted 
  by 
  Poitevin 
  and 
  Graham, 
  

   loc. 
  cit. 
  Optical 
  data 
  by 
  Wherry 
  on 
  specimen 
  kindly 
  furnished 
  by 
  Prof. 
  T. 
  L. 
  Walker. 
  

  

  6. 
  Colerainite 
  crystals, 
  Quebec. 
  Analysis 
  by 
  Connor; 
  optical 
  data 
  by 
  Poitevin 
  and 
  

   Graham. 
  

  

  ^ 
  Amer. 
  Jour. 
  vSci. 
  IV. 
  34: 
  475-476. 
  1912. 
  

  

  