﻿250 
  F. 
  W. 
  Clarice 
  and 
  E. 
  A. 
  Schneider 
  — 
  Constitution 
  of 
  

  

  and 
  negative, 
  though 
  the 
  axial 
  angle 
  is 
  small, 
  basal 
  plates 
  in 
  

   the 
  thin 
  section 
  showing 
  a 
  black 
  cross 
  which 
  scarcely 
  opens 
  at 
  

   all 
  during 
  the 
  revolution 
  of 
  the 
  stage. 
  Cleavage 
  plates 
  a 
  milli- 
  

   meter 
  or 
  more 
  in 
  thickness 
  show 
  plainly 
  the 
  biaxial 
  character, 
  

   though 
  the 
  figure 
  is 
  somewhat 
  distorted. 
  Dispersion 
  p 
  < 
  v. 
  

  

  The 
  surface 
  of 
  the 
  plates 
  is 
  at 
  times 
  plainly 
  marked 
  by 
  sharp 
  

   lines 
  crossing 
  at 
  angles 
  of 
  60° 
  and 
  120° 
  and 
  along 
  which 
  the 
  

   mineral 
  frequently 
  separates 
  readily. 
  Before 
  the 
  blowpipe 
  the 
  

   mineral 
  exfoliates 
  and 
  fuses 
  readily 
  on 
  the 
  edges 
  to 
  a 
  thin 
  

   glass." 
  

  

  According 
  to 
  Mr. 
  Merrill 
  this 
  mineral 
  is 
  sometimes 
  seen 
  in 
  

   cabinets 
  labelled 
  u 
  talc 
  ;" 
  and 
  indeed 
  in 
  its 
  appearance 
  it 
  resem- 
  

   bles 
  both 
  talc 
  and 
  serpentine. 
  Upon 
  analysis 
  the 
  following 
  

   results 
  were 
  obtained, 
  the 
  percentage 
  of 
  K 
  2 
  representing 
  two 
  

   identical 
  determinations. 
  

  

  Analysis. 
  Molec. 
  ratios. 
  

  

  Si0 
  2 
  43-71 
  -728 
  

  

  A1 
  2 
  G 
  3 
  3-59 
  -035 
  

  

  Fe 
  2 
  3 
  0-90 
  -006 
  

  

  MgO 
  38-58 
  -964 
  

  

  K 
  2 
  _. 
  ,.. 
  2-22 
  -023 
  

  

  Na 
  2 
  0/ 
  0-13 
  -002 
  

  

  H 
  2 
  0, 
  105° 
  0-46 
  

  

  " 
  250°-300° 
  0-09 
  

  

  " 
  ignition 
  10*70 
  -594 
  

  

  100-38 
  

  

  Treated 
  with 
  dry, 
  gaseous 
  HC1 
  at 
  383°-412° 
  for 
  16 
  J- 
  hours, 
  

   4-36 
  per 
  cent 
  of 
  magnesia 
  became 
  soluble, 
  corresponding 
  in 
  

   molecular 
  ratio 
  to 
  109 
  mol. 
  MgOH. 
  Hence 
  the 
  mineral, 
  

   although 
  resembling 
  serpentine 
  in 
  general 
  composition, 
  differs 
  

   from 
  the 
  latter 
  in 
  its 
  proportion 
  of 
  this 
  molecular 
  group. 
  

  

  Upon 
  treatment 
  with 
  aqueous 
  HC1 
  of 
  sp. 
  gr. 
  1*12, 
  a 
  small 
  

   portion 
  remained 
  undecomposed. 
  Ten 
  grams 
  of 
  the 
  mineral 
  

   were 
  therefore 
  digested 
  with 
  the 
  acid 
  for 
  three 
  days 
  on 
  the 
  

   water-bath, 
  and 
  the 
  residue 
  was 
  afterwards 
  boiled 
  out 
  with 
  a 
  

   solution 
  of 
  sodium 
  carbonate 
  to 
  remove 
  liberated 
  silica. 
  The 
  

   remaining 
  residue, 
  amounting 
  to 
  3*10 
  per 
  cent 
  of 
  the 
  original 
  

   material, 
  was 
  then 
  analyzed 
  separately, 
  and 
  found 
  to 
  contain 
  : 
  

  

  Si0 
  2 
  64-53 
  

  

  A1 
  2 
  U 
  3 
  , 
  Fe 
  2 
  8 
  2-03 
  

  

  MgO 
  33-04 
  

  

  99-60 
  

  

  All 
  the 
  potash 
  went 
  into 
  solution 
  ; 
  whence 
  it 
  seems 
  probable 
  

   that 
  no 
  muscovite 
  was 
  present. 
  The 
  ratios 
  of 
  the 
  insoluble 
  

   residue 
  agree 
  very 
  closely 
  with 
  those 
  of 
  talc, 
  and 
  we 
  may 
  there- 
  

  

  