﻿certain 
  Micas, 
  Vermiculites 
  and 
  Chlorites. 
  247 
  

  

  When 
  we 
  consider 
  the 
  nature 
  of 
  the 
  vermiculites, 
  as 
  products 
  

   of 
  alteration, 
  the 
  agreement 
  here 
  shown 
  is 
  fully 
  as 
  close 
  as 
  

   <30iild 
  be 
  expected. 
  Many 
  well 
  crystallized 
  minerals, 
  fresh 
  

   and 
  unaltered, 
  are 
  less 
  simply 
  interpreted. 
  

  

  On 
  the 
  19th 
  of 
  February, 
  1891, 
  Professor 
  Tschermak 
  read 
  

   before 
  the 
  Vienna 
  Academy 
  a 
  paper 
  on 
  the 
  chlorite 
  group, 
  in 
  

   which 
  he 
  referred 
  certain 
  vermiculites 
  to 
  that 
  class 
  of 
  minerals. 
  

   He 
  also 
  put 
  forth 
  some 
  views 
  concerning 
  the 
  constitution 
  of 
  

   the 
  chlorites, 
  which, 
  however, 
  we 
  cannot 
  discuss 
  until 
  they 
  

   have 
  been 
  published 
  in 
  full.* 
  One 
  fundamental 
  molecule, 
  

   regarded 
  by 
  Tschermak 
  as 
  a 
  constituent 
  of 
  most 
  chlorites, 
  we 
  

   may 
  adopt 
  for 
  present 
  purposes, 
  under 
  slightly 
  different 
  struc- 
  

   tural 
  form 
  from 
  his. 
  This 
  is 
  the 
  "amesite 
  substance, 
  SiAl 
  2 
  

   Mg 
  2 
  H 
  4 
  9 
  , 
  written 
  by 
  Tschermak 
  SiAl 
  2 
  H 
  2 
  7 
  (MgOH) 
  2 
  . 
  In 
  de- 
  

   fault 
  of 
  experimental 
  evidence 
  this 
  may 
  be 
  transformed 
  into 
  

   OMg 
  2 
  Si 
  4 
  (AlH 
  2 
  2 
  ) 
  2 
  , 
  when 
  it 
  becomes 
  part 
  of 
  a 
  natural 
  chloritic 
  

   series 
  parallel 
  with 
  the 
  micas 
  — 
  thus 
  : 
  

  

  Normal 
  orthosilicate 
  Al 
  4 
  (SiO 
  J, 
  Mg 
  4 
  (Si0 
  4 
  ) 
  2 
  

  

  Whence 
  we 
  derive, 
  Micas. 
  Chlorites. 
  

  

  Al 
  3 
  (Si0 
  4 
  ) 
  3 
  R' 
  3 
  Mg 
  3 
  (Si0 
  4 
  ) 
  2 
  R' 
  2 
  

  

  Al 
  2 
  (Si0 
  4 
  ),R' 
  6 
  Mg,(Si0 
  4 
  ) 
  a 
  R' 
  4 
  

  

  Al 
  (Si0 
  4 
  ) 
  3 
  R' 
  9 
  Mg'(Si0 
  4 
  ) 
  2 
  R' 
  6 
  

  

  Al-O/* 
  1 
  / 
  )Si0 
  4 
  =R' 
  

  

  \SiO=R' 
  3 
  ^Mg' 
  

  

  In 
  other 
  words, 
  the 
  " 
  amesite 
  substance 
  " 
  in 
  our 
  chlorite 
  series 
  

   is 
  the 
  basic 
  equivalent 
  of 
  the 
  clintonite 
  molecule 
  among 
  the 
  

   micas, 
  and 
  is 
  applicable 
  to 
  the 
  solution 
  of 
  certain 
  obscure 
  

   problems. 
  Some 
  of 
  the 
  vermiculites, 
  as 
  Tschermak 
  suggests, 
  

   are 
  probably 
  chlorites, 
  and 
  two 
  examples 
  have 
  come 
  under 
  our 
  

   notice 
  in 
  which 
  this 
  view 
  is 
  partly 
  sustained. 
  Both 
  were 
  

   originally 
  received 
  from 
  Mr. 
  Jefferis 
  ; 
  one 
  from 
  the 
  corundum 
  

   mine 
  at 
  Newlin, 
  Chester 
  County, 
  Pa., 
  and 
  the 
  other 
  from 
  

   Middletown, 
  Delaware 
  County, 
  in 
  the 
  same 
  State. 
  The 
  New- 
  

   lin 
  mineral 
  was 
  dull 
  green, 
  and 
  much 
  resembled 
  culsageeite 
  

   both 
  outwardly 
  and 
  optically. 
  The 
  Middletown 
  vermiculite 
  

   was 
  bright 
  golden 
  yellow 
  ; 
  strongly 
  exfoliating 
  before 
  the 
  

   blowpipe 
  and 
  fusible 
  on 
  the 
  edges. 
  It 
  was 
  found 
  upon 
  the 
  

   farm 
  of 
  Mr. 
  James 
  Painter, 
  whence 
  Mr. 
  Jefferis 
  'named 
  it 
  

   provisionally 
  " 
  Painterite," 
  a 
  name 
  which 
  seems 
  also 
  to 
  have 
  

   been 
  applied 
  to 
  a 
  peculiar 
  brownish, 
  waxy, 
  feldspathic 
  matrix 
  

   in 
  which 
  the 
  broad 
  golden 
  laminae 
  were 
  imbedded. 
  A 
  second 
  

   sample 
  of 
  it 
  was 
  later 
  collected 
  by 
  one 
  of 
  us. 
  According 
  to 
  

  

  * 
  This 
  paper 
  has 
  appeared 
  in 
  extenso 
  since 
  this 
  was 
  written. 
  We 
  cannot, 
  how- 
  

   ever, 
  discuss 
  it 
  thoroughly 
  at 
  present. 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Thiud 
  Series, 
  Vol. 
  XLII, 
  No. 
  249. 
  — 
  September, 
  1891. 
  

   17 
  

  

  