﻿Brackett 
  and 
  Williams 
  — 
  Newtonite 
  and 
  Rectorite. 
  15 
  

  

  these 
  analyses, 
  kindly 
  furnished 
  the 
  information 
  that 
  the 
  cal- 
  

   culations 
  are 
  made 
  on 
  the 
  air-dried 
  material, 
  and 
  that 
  in 
  analy- 
  

   sis 
  III, 
  8*68 
  per 
  cent 
  of 
  the 
  loss 
  on 
  ignition 
  is 
  given 
  off 
  at 
  about 
  

   110° 
  C. 
  

  

  If 
  analyses 
  la 
  and 
  Ila 
  be 
  calculated 
  to 
  the 
  air-dried 
  mate- 
  

   rial 
  the 
  difference 
  between 
  them 
  and 
  the 
  published 
  analyses 
  of 
  

   halloysite 
  is 
  clearly 
  shown, 
  as 
  is 
  evident 
  from 
  a 
  consideration 
  of 
  

   the 
  following 
  table 
  : 
  

  

  lb. 
  lib. 
  Halloysite. 
  

  

  Si0 
  2 
  36-83 
  3796 
  39'35 
  

  

  A1 
  2 
  3 
  33-42 
  33-34 
  3635 
  

  

  Loss 
  on 
  ignition 
  ._ 
  24'22 
  23'26 
  14-22 
  

  

  Water 
  at 
  110°-115° 
  C. 
  ..- 
  5-53 
  5'44 
  8'68 
  (at 
  100° 
  C.) 
  

  

  100-00 
  100-00 
  98-60 
  

  

  If 
  it 
  be 
  assumed 
  that 
  the 
  8 
  68 
  per 
  cent 
  of 
  water 
  in 
  halloysite 
  

   is 
  partly 
  hygroscopic 
  and 
  partly 
  water 
  of 
  crystallization, 
  this 
  

   mineral 
  would 
  have 
  the 
  composition 
  of 
  kaolinite 
  containing 
  

   one 
  molecule 
  of 
  water 
  of 
  crystallization. 
  Judging 
  from 
  the 
  

   newtonite 
  analyses 
  lb 
  and 
  lib, 
  this 
  substance 
  would, 
  under 
  

   like 
  circumstances, 
  have 
  one 
  molecule 
  of 
  water 
  of 
  crystalliza- 
  

   tion, 
  but 
  would 
  be 
  represented 
  by 
  the 
  formula 
  A1 
  2 
  3 
  . 
  2Si0 
  2 
  . 
  

   4H 
  2 
  + 
  aq, 
  while 
  the 
  composition 
  of 
  halloysite 
  would 
  be 
  ex- 
  

   pressed 
  by 
  the 
  formula 
  A1 
  2 
  3 
  . 
  2Si0 
  2 
  . 
  2H 
  2 
  + 
  aq. 
  

  

  Ordinary 
  kaolin 
  usually 
  contains 
  less 
  than 
  one 
  per 
  cent 
  of 
  

   loosely 
  combined 
  water. 
  Hydrous 
  silicates 
  of 
  alumina 
  have, 
  

   however, 
  been 
  analyzed 
  in 
  this 
  laboratory, 
  which 
  have 
  given 
  oft' 
  

   as 
  much 
  as 
  five 
  per 
  cent 
  of 
  water 
  at 
  110° 
  C, 
  but 
  which 
  differ 
  

   from 
  ordinary 
  kaolin 
  in 
  no 
  other 
  respect, 
  and 
  it 
  is 
  probable 
  

   that 
  differences 
  in 
  origin 
  and 
  occurrence 
  will 
  account 
  for 
  these 
  

   varying 
  amounts 
  of 
  loosely 
  combined 
  water. 
  

  

  A 
  thin 
  section 
  of 
  newtonite 
  under 
  the 
  microscope 
  when 
  

   viewed 
  only 
  with 
  low 
  powers 
  appears 
  as 
  a 
  perfectly 
  amorphous 
  

   substance 
  but 
  when 
  magnified 
  to 
  four 
  or 
  five 
  hundred 
  diam- 
  

   eters 
  it 
  shows 
  that 
  it 
  is 
  entirely 
  made 
  up 
  of 
  minute 
  rhombs 
  or 
  

   squares. 
  The 
  largest 
  of 
  these 
  are 
  not 
  more 
  than 
  0'005 
  mm 
  (-5-^7 
  

   of 
  an 
  inch) 
  on 
  an 
  edge, 
  while 
  the 
  smallest 
  appear 
  to 
  be 
  about 
  

   half 
  that 
  size. 
  Sometimes 
  they 
  seem 
  to 
  form 
  perfect 
  squares 
  

   but 
  in 
  the 
  majority 
  of 
  cases 
  the 
  acute 
  angles 
  have 
  values 
  rang- 
  

   ing 
  from 
  88° 
  to 
  89°, 
  as 
  nearly 
  as 
  could 
  be 
  measured. 
  There 
  

   appear 
  between 
  these 
  minute 
  figures 
  blank 
  spaces 
  where 
  noth- 
  

   ing 
  can 
  at 
  first 
  be 
  seen, 
  but 
  by 
  sinking 
  the 
  microscope 
  tube 
  

   somewhat, 
  so 
  as 
  to 
  focus 
  a 
  little 
  lower 
  down, 
  an 
  entirely 
  new 
  

   set 
  of 
  rhombs 
  is 
  discovered, 
  while 
  those 
  above 
  go 
  out 
  of 
  focus. 
  

   At 
  first 
  sight 
  all 
  the 
  rhombs 
  appear 
  as 
  squares 
  and 
  show 
  small 
  

   indistinct 
  lines 
  running 
  from 
  their 
  corners 
  toward 
  the 
  center, 
  

   giving 
  the 
  appearance 
  of 
  the 
  hopper-shaped 
  crystals 
  of 
  salt. 
  

  

  