﻿244 
  F. 
  W. 
  Clarke 
  and 
  E. 
  A. 
  Schneider 
  — 
  Constitution 
  of 
  

  

  

  

  

  Henderson 
  Go, 
  

  

  Protovermiculite. 
  

  

  

  

  

  Found. 
  

  

  Calc. 
  

  

  Found. 
  

  

  Calc. 
  

  

  Si0 
  2 
  

  

  

  

  39-70 
  

  

  39 
  90 
  

  

  34-10 
  

  

  34-18 
  

  

  A1A 
  

  

  

  

  14-12 
  

  

  14-25 
  

  

  14-52 
  

  

  14-78 
  

  

  Fe 
  2 
  0, 
  

  

  

  

  13-11 
  

  

  13-15 
  

  

  7-72 
  

  

  7-20 
  

  

  MgO 
  

  

  

  

  16-32 
  

  

  17-08 
  

  

  22-41 
  

  

  22-79 
  

  

  K 
  2 
  

  

  

  

  6-17 
  

  

  6-17 
  

  

  

  

  

  

  H 
  2 
  0, 
  

  

  essential 
  

  

  4-83 
  

  

  4-87 
  

  

  5-43 
  

  

  5-40 
  

  

  u 
  

  

  hy 
  

  

  dration 
  5*75 
  

  

  4-58 
  

  

  15-82 
  

  

  15-65 
  

  

  100-00 
  100-00 
  100-00 
  100*00 
  

  

  These 
  results, 
  taken 
  in 
  connection 
  with 
  our 
  work 
  on 
  jefferi- 
  

   site 
  and 
  kerrite, 
  and 
  with 
  the 
  mica 
  theory 
  upon 
  which 
  all 
  our 
  

   formulse 
  are 
  based, 
  are 
  exceedingly 
  suggestive. 
  Kerrite 
  is 
  

   essentially 
  a 
  trihyd 
  rated 
  hydro-phlogopite. 
  Protovermiculite 
  

   is 
  the 
  same 
  substance, 
  commingled 
  with 
  a 
  tri-hydrated 
  hydro- 
  

   clintonite, 
  in 
  the 
  ratio 
  1 
  : 
  1 
  very 
  nearly. 
  Jefferisite 
  is 
  a 
  similar 
  

   mixture 
  of 
  hydro-biotite 
  and 
  hydro 
  clintonite, 
  also 
  trihydrated, 
  

   and 
  in 
  the 
  ratio 
  1 
  : 
  1. 
  The 
  Henderson 
  County 
  mica 
  is 
  essen- 
  

   tially 
  a 
  biotite, 
  about 
  half 
  way 
  transformed 
  into 
  a 
  vermiculite, 
  

   and 
  is 
  interesting 
  as 
  a 
  transition 
  product. 
  The 
  hydration 
  of 
  

   its 
  several 
  admixed 
  molecules 
  is 
  naturally 
  uncertain. 
  At 
  an 
  

   early 
  date 
  we 
  hope 
  to 
  imitate 
  experimentally 
  the 
  process 
  by 
  

   which 
  a 
  mica 
  becomes 
  transformed 
  into 
  its 
  corresponding 
  

   vermiculite. 
  

  

  But 
  although 
  the 
  above-named 
  minerals 
  appear 
  to 
  be 
  very 
  

   simple 
  in 
  their 
  structure 
  and 
  relationships, 
  a 
  like 
  simplicity 
  

   does 
  not 
  characterize 
  all 
  of 
  the 
  vermiculites. 
  In 
  some 
  mem- 
  

   bers 
  of 
  the 
  group 
  there 
  seem 
  to 
  be 
  a 
  small 
  admixture 
  of 
  chlo- 
  

   ritic 
  molecules, 
  and 
  it 
  is 
  even 
  probable 
  that 
  many 
  intermediate 
  

   stages 
  between 
  mica 
  and 
  chlorite 
  may 
  exist. 
  As 
  bearing 
  upon 
  

   this 
  question 
  we 
  have 
  a 
  series 
  of 
  vermiculitic 
  minerals 
  from 
  

   Chester 
  and 
  Delaware 
  Counties, 
  Pennsylvania, 
  some 
  of 
  which 
  

   have 
  already 
  been 
  studied 
  by 
  Cooke, 
  Gooch, 
  Leeds 
  and 
  others, 
  

   while 
  some 
  have 
  escaped 
  examination 
  hitherto. 
  To 
  begin 
  

   with 
  we 
  may 
  consider 
  the 
  hallite, 
  from 
  Nottingham, 
  Chester 
  

   County, 
  and 
  the 
  vermiculites 
  from 
  Lenni, 
  (not 
  Lerni), 
  Delaware 
  

   County. 
  The 
  hallite, 
  received 
  through 
  the 
  kindness 
  of 
  Mr. 
  

   W. 
  W. 
  Jefferis, 
  was 
  dark 
  bluish 
  green, 
  and 
  agreed 
  perfectly 
  

   with 
  the 
  published 
  descriptions. 
  The 
  Lenni 
  mineral, 
  partly 
  

   from 
  the 
  collection 
  of 
  the 
  late 
  Isaac 
  Lea, 
  and 
  partly 
  gathered 
  

   in 
  the 
  field 
  by 
  one 
  of 
  us, 
  is 
  represented 
  by 
  several 
  varieties, 
  

   which 
  in 
  a 
  large 
  series 
  of 
  specimens, 
  are 
  seen 
  to 
  shade 
  into 
  

   each 
  other. 
  Three 
  varieties 
  were 
  examined 
  : 
  one, 
  silver 
  white, 
  

   resembling 
  outwardly 
  an 
  ordinary 
  mica 
  ; 
  a 
  second, 
  bronzy 
  

   brown, 
  like 
  jefferisite 
  ; 
  and 
  the 
  third, 
  dark 
  green, 
  similar 
  to 
  

   clinochlore. 
  All 
  four 
  substances 
  were 
  examined 
  microscopi- 
  

  

  