﻿CLAYS 
  OF 
  NEW 
  YOKK 
  

  

  505 
  

  

  Halloysite. 
  A 
  massive, 
  clay-like 
  or 
  earthy 
  mineral, 
  with 
  a 
  

   conchoidal 
  fracture. 
  It 
  shows 
  little 
  or 
  no 
  plasticity. 
  It 
  has 
  a 
  

   hardness 
  of 
  1-2. 
  The 
  specific 
  gravity 
  is 
  2.0-2.20. 
  The 
  luster 
  is 
  

   somewhat 
  pearly 
  to 
  waxy 
  or 
  dull. 
  The 
  color 
  is 
  white, 
  grayish, 
  

   greenish, 
  yellowish 
  and 
  reddish. 
  It 
  is 
  translucent 
  to 
  opaque, 
  some- 
  

   times 
  becoming 
  translucent 
  or 
  even 
  transparent 
  in 
  water, 
  vdth 
  an 
  

   increase 
  of 
  one 
  fifth 
  in 
  weight. 
  It 
  is 
  a 
  silicate 
  of 
  alumina 
  like 
  

   kaolinite, 
  but 
  am.orphou8 
  and 
  containing 
  more 
  water; 
  the 
  amount 
  

   is 
  somewhat 
  uncertain, 
  but 
  according 
  to 
  Le 
  Chatelier 
  the 
  composi- 
  

   tion 
  is 
  probably 
  2U2O, 
  AI2O3 
  2Si02+ 
  aq, 
  or 
  silica 
  43.5^, 
  alumina 
  

   36.9/'^, 
  water 
  19.6^= 
  100. 
  It 
  is 
  not 
  uncommon 
  in 
  the 
  kaolin 
  de- 
  

   posits 
  around 
  Yalleyhead, 
  Dekalb 
  co. 
  Ala., 
  where 
  it 
  occurs 
  as 
  

   veins 
  in 
  the 
  kaolin. 
  

  

  Rectorite. 
  Monoclinic. 
  In 
  leaves 
  or 
  plates 
  resembling 
  moun- 
  

   tain 
  leather. 
  Very 
  soft, 
  hardness 
  less 
  than 
  that 
  of 
  talc. 
  Feels 
  

   soapy. 
  Luster 
  pearly. 
  Color 
  pure 
  white, 
  sometimes 
  stained 
  red 
  

   with 
  iron 
  oxid. 
  Composition 
  : 
  H 
  Al 
  Si04 
  or 
  AI2O3, 
  2 
  fSiOg, 
  H20= 
  

   silica 
  50.0; 
  alumina 
  42.6; 
  water 
  7.5. 
  

  

  Newtonite. 
  Rhombohedral. 
  In 
  soft, 
  compact 
  masses, 
  resem- 
  

   bling 
  kaolinite. 
  Color 
  white. 
  Composition: 
  H8A]2SJ20ii-4-water 
  

   or 
  AI2O3, 
  ii 
  SiOo, 
  5 
  HaO-^silica 
  3:^.5, 
  alumina 
  32.7, 
  water 
  28.8. 
  

   Sp. 
  gr. 
  = 
  2.3L 
  

  

  AUophane. 
  Amorphous. 
  As 
  incrustations 
  which 
  are 
  usually 
  

  

  thin, 
  v^ith 
  mammillary 
  surface. 
  Occasionally 
  almost 
  pulverulent. 
  

   Fracture 
  imperfectly 
  conchoidal 
  and 
  shining, 
  to 
  earthy. 
  Very 
  

   brittle. 
  Color 
  variable. 
  Translucent. 
  A 
  hydrous 
  aluminum 
  sili- 
  

   cite, 
  Al2^i05-|-5H20=silica 
  :43.8, 
  alumina 
  40.5, 
  water 
  35.7. 
  

   Hardness 
  :^. 
  Sp. 
  gr. 
  1.85—1 
  S'.\ 
  

  

  Other 
  species 
  listed 
  by 
  Dana 
  in 
  the 
  kaolinite 
  gi'oup 
  are 
  cimolite, 
  

   montmorillonite, 
  pyrophyllite, 
  collyrite 
  and 
  Schrotterite. 
  Indian- 
  

   aite, 
  SL 
  white 
  residual 
  clay 
  found 
  in 
  Lawrence 
  co. 
  Ind., 
  is 
  placed 
  

   under 
  halloysite 
  by 
  Dana. 
  

  

  Clays 
  may 
  vary 
  mineralogically 
  within 
  very 
  mde 
  limits. 
  Pure 
  

   clay, 
  as 
  before 
  stated, 
  would 
  consist 
  entirely 
  of 
  the 
  mineral 
  kaolin- 
  

   ite, 
  but 
  in 
  addition 
  to 
  this 
  quartz, 
  feldspar 
  and 
  mica 
  are 
  minerals 
  

  

  