﻿Vander 
  Meulen 
  — 
  Two 
  So-called 
  Halloy 
  sites. 
  141 
  

  

  vacuum 
  pump 
  in 
  the 
  usual 
  manner. 
  The 
  results 
  on 
  the 
  air 
  

   dried 
  material 
  are 
  given 
  below 
  (No. 
  I 
  of 
  table). 
  

  

  The 
  second 
  clay 
  (No. 
  II 
  of 
  table), 
  which 
  comes 
  from 
  the 
  

   Fort 
  Faine 
  Chert 
  formation 
  in 
  Northern 
  Alabama, 
  contained 
  

   no 
  good 
  crystals, 
  but 
  showed 
  a 
  very 
  few 
  small 
  nodules 
  of 
  a 
  

   substance 
  resembling 
  bauxite 
  in 
  appearance. 
  The 
  results 
  of 
  

   the 
  analysis 
  and 
  the 
  specific 
  gravity 
  are 
  given 
  herewith. 
  

  

  Analyses 
  of 
  Halloysite. 
  

  

  I 
  II 
  III 
  IV 
  

  

  SiO 
  a 
  35*82^ 
  43*30^ 
  41*69$ 
  43*18$ 
  

  

  A1 
  9 
  U 
  3 
  .._ 
  __. 
  44*38 
  39*94 
  35-88 
  39-21 
  

  

  Fe„O 
  s 
  tr. 
  tr. 
  '37 
  *15 
  

  

  CaO 
  none 
  none 
  *06 
  none 
  

  

  MgO 
  tr. 
  -21 
  tr. 
  

  

  Na 
  2 
  .__ 
  1*18 
  *25 
  -08 
  

  

  K 
  2 
  ._. 
  .- 
  none 
  none 
  none 
  

  

  H 
  2 
  below 
  108° 
  C... 
  1*61 
  1*28 
  7*97 
  3'39 
  

  

  H 
  2 
  above 
  108° 
  16'63 
  15*04 
  14-01 
  14*23 
  

  

  Total 
  99*62 
  100-02 
  99*98 
  100*24 
  

  

  Sp.gr. 
  20 
  C. 
  2*497 
  2*441 
  2*460 
  

  

  The 
  results 
  of 
  these 
  analyses 
  show 
  the 
  clays 
  to 
  have 
  a 
  water 
  

   content 
  below 
  that 
  of 
  halloysite, 
  while 
  the 
  specific 
  gravity 
  is 
  

   higher, 
  for 
  that 
  of 
  halloysite 
  is 
  usually 
  given 
  as 
  2*0-2*2. 
  An 
  

   analysis 
  of 
  halloysite 
  (No. 
  Ill) 
  from 
  Horse 
  Cave, 
  Ky., 
  by 
  H. 
  

   C. 
  McNeil* 
  is 
  given 
  for 
  purposes 
  of 
  comparison. 
  Analysis 
  

   No. 
  IV, 
  made 
  by 
  the 
  author, 
  of 
  a 
  sample 
  of 
  clay 
  which 
  goes 
  

   under 
  the 
  name 
  of 
  halloysite, 
  from 
  Grubb 
  Mines, 
  near 
  Roan- 
  

   oke, 
  Virginia, 
  is 
  included 
  because 
  it 
  has 
  a 
  somewhat 
  higher 
  

   alumina-silica 
  ratio 
  than 
  does 
  halloysite 
  of 
  the 
  usually 
  accepted 
  

   composition, 
  but 
  agrees 
  with 
  it 
  in 
  the 
  properties 
  ascribed 
  to 
  

   this 
  substance 
  by 
  Dana. 
  

  

  The 
  clays 
  above 
  described 
  also 
  contain 
  a 
  higher 
  percentage 
  

   of 
  alumina 
  than 
  halloysite, 
  and 
  agree 
  closely 
  in 
  chemical 
  com- 
  

   position 
  with 
  the 
  high 
  alumina 
  flint 
  clays 
  described 
  by 
  Greaves- 
  

   Walker.f 
  These 
  clays 
  are, 
  therefore, 
  not 
  halloysite. 
  

  

  There 
  is 
  a 
  good 
  deal 
  of 
  doubt 
  concerning 
  the 
  compounds 
  

   present 
  in 
  clay 
  mixtures 
  such 
  as 
  those 
  under 
  discussion, 
  espe- 
  

   cially 
  when 
  the 
  material 
  is 
  so 
  very 
  fine-grained 
  that 
  a 
  micro- 
  

   scopic 
  examination 
  does 
  not 
  even 
  give 
  a 
  clue 
  as 
  to 
  any 
  of 
  the 
  

   constituents. 
  It 
  is 
  exceedingly 
  unsafe 
  to 
  calculate 
  the 
  mineral 
  

   composition 
  of 
  a 
  clay 
  from 
  its 
  chemical 
  analysis.;}; 
  The 
  com- 
  

   pound 
  assumed 
  by 
  many 
  to 
  be 
  present 
  in 
  practically 
  ail 
  clays 
  is 
  

   kaolinite, 
  to 
  which 
  the 
  formula 
  H 
  4 
  Al 
  2 
  Si 
  2 
  9 
  is 
  usually 
  assigned, 
  

  

  *U. 
  S. 
  G. 
  S. 
  Bull. 
  591, 
  p. 
  345. 
  fTr. 
  Am. 
  Oer. 
  Soc, 
  viii, 
  297. 
  

  

  JH. 
  Ries, 
  Econ. 
  Geol., 
  ix, 
  402, 
  1914. 
  

  

  