﻿242 
  F. 
  W. 
  Clarice 
  and 
  K 
  A. 
  Schneider 
  — 
  Constitution 
  of 
  

  

  Art. 
  XXIII. 
  — 
  On 
  the 
  Constitution 
  of 
  certain 
  Micas, 
  Ver- 
  

   miculites 
  and 
  Chlorites 
  ; 
  by 
  F. 
  W. 
  Clarke 
  and 
  E. 
  A. 
  

   Schneider. 
  

  

  In 
  a 
  previous 
  paper 
  upon 
  the 
  constitution 
  of 
  the 
  silicates,* 
  

   we 
  sought 
  to 
  establish 
  some 
  new 
  lines 
  of 
  attack 
  upon 
  the 
  

   problem, 
  especially 
  with 
  reference 
  to 
  the 
  mica 
  and 
  chlorite 
  

   groups. 
  The 
  present 
  communication 
  is 
  to 
  be 
  regarded 
  as 
  a 
  

   continuation 
  of 
  the 
  same 
  research, 
  and 
  by 
  essentially 
  the 
  same 
  

   methods 
  ; 
  although 
  in 
  some 
  instances 
  the 
  experiments 
  have 
  

   been 
  less 
  elaborate, 
  when 
  elaborateness 
  seemed 
  to 
  be 
  unneces- 
  

   sary. 
  Throughout 
  the 
  investigation 
  the 
  fundamental 
  hypoth- 
  

   esis 
  that 
  the 
  minerals 
  studied 
  are 
  substitution 
  derivatives 
  of 
  

   normal 
  salts 
  has 
  been 
  kept 
  steadily 
  in 
  view 
  ; 
  and, 
  as 
  we 
  believe, 
  

   it 
  has 
  been 
  amply 
  justified. 
  

  

  Of 
  the 
  so-called 
  vermiculites, 
  two 
  only, 
  jefferisite 
  and 
  kerrite, 
  

   were 
  considered 
  in 
  our 
  former 
  paper 
  ; 
  and 
  these 
  were 
  shown 
  

   to 
  be 
  trihydrated 
  micas, 
  in 
  which 
  the 
  original 
  alkalies 
  had 
  

   been 
  replaced 
  by 
  hydrogen. 
  To 
  these 
  examples 
  we 
  now 
  add 
  

   several 
  others; 
  of 
  which 
  two 
  varieties 
  afford 
  excellent 
  checks 
  

   upon 
  the 
  earlier 
  work. 
  The 
  two 
  minerals 
  in 
  question 
  are 
  an 
  

   altered 
  biotite 
  from 
  the 
  zircon 
  mine 
  in 
  Henderson 
  County, 
  

   N. 
  C, 
  and 
  the 
  protovermiculite 
  from 
  Magnet 
  Cove, 
  Arkansas, 
  

   described 
  some 
  years 
  ago 
  by 
  Kcenig. 
  The 
  analyses, 
  with 
  

   itemized 
  water 
  determinations, 
  are 
  as 
  follows 
  : 
  

  

  Henderson 
  Co. 
  Protovermiculite. 
  

  

  Analysis. 
  Mol. 
  ratio. 
  Analysis. 
  Mol. 
  ratio. 
  

  

  SiO 
  a 
  38-18 
  -636 
  34-03 
  5*67 
  

  

  Ti0 
  2 
  1*68 
  -021 
  undet. 
  

  

  Zr0 
  2 
  ... 
  none 
  — 
  

  

  A1 
  2 
  3 
  14-02 
  -138 
  14-49 
  -142 
  

  

  Fe 
  2 
  3 
  ._. 
  13-02 
  -081 
  7-71 
  *048 
  

  

  FeO 
  2-22 
  '031 
  0-14 
  *0G2 
  

  

  MnO 
  0-38 
  '005 
  0'09 
  '001 
  

  

  MgO 
  14-62 
  -385 
  20-89 
  '522 
  

  

  CaO 
  0-17 
  '003 
  1-88 
  '034 
  

  

  BaO 
  0-06 
  

  

  K 
  2 
  5-40 
  -057 
  

  

  Na 
  2 
  0-48 
  -008 
  

  

  H 
  2 
  0, 
  305° 
  3-20 
  -178 
  11-23 
  *624 
  

  

  " 
  250°-300° 
  2-52 
  '140 
  4*55 
  '253 
  

  

  " 
  above 
  300° 
  __ 
  4'SO 
  -267 
  5*41 
  -301 
  

  

  100-75 
  100-42 
  

  

  H 
  2 
  over 
  II 
  a 
  S0 
  4 
  .-. 
  3-20 
  11-34 
  

  

  *This 
  Journal, 
  Oct., 
  Nov. 
  and 
  Dec, 
  1890. 
  

  

  