﻿600 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  . 
  

  

  If 
  ]Mr 
  Collinses 
  theory 
  be 
  correct, 
  the 
  kaolin 
  deposits 
  should 
  

   extend 
  to 
  great 
  depths, 
  but 
  if 
  the 
  kaolinization 
  be 
  due 
  to 
  weathering^ 
  

   then 
  we 
  should 
  encounter 
  undecomposed 
  feldspar 
  at 
  the 
  limit 
  to 
  

   which 
  weathering 
  has 
  reached. 
  In 
  Cornwall 
  the 
  kaolin 
  mines, 
  

   which 
  are 
  probably 
  the 
  largest 
  in 
  the 
  world, 
  have 
  reached 
  a 
  depth 
  

   of 
  over 
  200 
  feet 
  without 
  the 
  kaolin 
  giving 
  out, 
  wliile 
  at 
  Zcttlitz 
  

   in 
  Bohemia 
  a 
  depth 
  of 
  over 
  400 
  feet 
  has 
  been 
  reached 
  with 
  the 
  

   same 
  result. 
  The 
  latter 
  locality 
  is 
  one 
  of 
  thermal 
  activity. 
  In 
  

   these 
  two 
  instances 
  th.e 
  theory 
  just 
  mentioned 
  seems 
  to 
  be 
  very 
  

   reasonable. 
  There 
  are 
  many 
  localities 
  howeA^er 
  where 
  the 
  kaolin 
  

   decreases 
  with 
  the 
  depth, 
  passing 
  into 
  the 
  undecomposed 
  feldspar^ 
  

   as 
  is 
  the 
  case 
  for 
  example 
  in 
  J^orth 
  Carolina, 
  where 
  the 
  fresh 
  

   feldspar 
  is 
  met 
  at 
  a 
  depth 
  of 
  60' 
  to 
  120 
  feet. 
  Still 
  there 
  are 
  locali- 
  

   ties 
  in 
  the 
  United 
  States 
  where 
  the 
  mineralizing 
  vapors 
  seem 
  clearly 
  

   to 
  have 
  aided 
  in 
  the 
  fo'rmation 
  of 
  kaolinite. 
  Thus 
  in 
  many 
  of 
  the 
  

   mines 
  at 
  Cripplecreek 
  in 
  Colorado, 
  kaolinite 
  has 
  been 
  produced 
  

   by 
  the 
  decomposition 
  of 
  the 
  feldspar, 
  and 
  is 
  considered 
  by 
  Penrose- 
  

   to 
  have 
  been 
  formed 
  by 
  other 
  agencies 
  than 
  those 
  of 
  weathering; 
  

   for 
  the 
  reason 
  that 
  it 
  shows^ 
  no 
  sign 
  of 
  decrease 
  in 
  quantity 
  mth 
  

   the 
  depth, 
  occurring 
  as 
  abundantly 
  in 
  the 
  bottom 
  of 
  the 
  deepest 
  

   mines 
  as 
  on 
  the 
  surface. 
  The 
  frequent 
  association 
  with 
  it 
  of 
  the 
  

   unaltered 
  sulfid 
  minerals 
  suggests 
  that 
  superficial 
  alteration 
  had 
  

   no 
  part 
  in 
  the 
  formation 
  of 
  the 
  kaolinite, 
  otherwise 
  the 
  sulfids 
  

   would 
  have 
  been 
  oxidized 
  to 
  sulfate^. 
  It 
  is 
  possible 
  that 
  fluorin 
  

   may 
  have 
  been 
  the 
  agent 
  in 
  the 
  change, 
  for 
  it 
  is 
  abundant 
  in 
  many 
  

   of 
  the 
  Cripplecreek 
  ore 
  deposits. 
  

  

  Whatever 
  the 
  species 
  of 
  feldspar, 
  or 
  the 
  process 
  of 
  decomposition, 
  

   the 
  product 
  is 
  kaolinite, 
  and, 
  as 
  previously 
  observed, 
  a 
  mass 
  of 
  

   kaolinite 
  would 
  be 
  termed 
  kaolin, 
  or 
  pure 
  clay. 
  Such 
  a 
  thing 
  as 
  

   pure 
  clay 
  is 
  however 
  unknown, 
  for 
  one 
  or 
  more 
  minerals 
  are 
  

   always 
  associated 
  with 
  the 
  feldspar 
  and 
  remain 
  in 
  the 
  kaolin 
  as- 
  

   impurities, 
  but 
  not 
  necessarily 
  injurious 
  ones. 
  Clay 
  therefore 
  is 
  

   formed 
  primarily 
  by 
  the 
  decomposition 
  of 
  a 
  feldspatliic 
  rock 
  mass,. 
  

  

  ^ 
  U. 
  S. 
  geol. 
  sur. 
  IQth 
  ann. 
  rep't 
  pt 
  2, 
  p. 
  i.'6\. 
  

  

  