﻿CLAYS 
  OF 
  NEW 
  YORK 
  781 
  

  

  FIEE 
  CLAYS 
  

  

  Definition. 
  Strictly 
  speaking 
  the 
  term 
  fire 
  clay 
  can 
  be 
  said 
  to 
  

   include 
  those 
  clays 
  which 
  are 
  able 
  to 
  withstand 
  a 
  high 
  temperature. 
  

   Regarding 
  the 
  condition 
  of 
  the 
  plasticity, 
  the 
  shrinkage 
  in 
  drying 
  

   and 
  burning, 
  the 
  texture, 
  and 
  color, 
  no 
  fixed 
  rules 
  can 
  be 
  laid 
  

   down; 
  for, 
  except 
  in 
  refractoriness, 
  fire 
  clays 
  show 
  a 
  wide 
  variation 
  

   in 
  physical 
  characters. 
  

  

  Refractoriness. 
  The 
  degree 
  of 
  temperature 
  which 
  a 
  fire 
  clay 
  

   should 
  be 
  able 
  to 
  withstand 
  without 
  fusing 
  has 
  not 
  been 
  entirely 
  

   settled 
  in 
  this 
  country, 
  but 
  in 
  Europe, 
  specially 
  in 
  Germany, 
  a 
  clay 
  

   is 
  not 
  considered 
  refractory 
  unless 
  its 
  fusing 
  point 
  lies 
  above 
  

   2700° 
  F. 
  

  

  E^evertheless 
  many 
  of 
  the 
  clays 
  denominated 
  fire 
  clays 
  which 
  

   are 
  marketed 
  in 
  this 
  country 
  are 
  not 
  up 
  to 
  this 
  standard, 
  while 
  

   others 
  are 
  far 
  above 
  it. 
  The 
  color 
  of 
  fire 
  clays 
  varies, 
  but 
  they 
  

   are 
  not 
  infrequently 
  colored 
  bluish 
  gray, 
  gray 
  or 
  black 
  by 
  organic 
  

   matter. 
  Some 
  of 
  those 
  mined 
  on 
  Staten 
  Island 
  are 
  pure 
  white 
  or 
  

   yellowish 
  white, 
  but 
  at 
  the 
  same 
  time 
  they 
  are 
  highly 
  refractory. 
  

  

  Fire 
  clays 
  are 
  divisible 
  into 
  two 
  groups, 
  the 
  plastic, 
  and 
  the 
  non- 
  

   plastic 
  or 
  flint 
  clays. 
  The 
  former 
  sometimes 
  occur 
  in 
  the 
  form 
  

   of 
  hard 
  shales 
  which 
  become 
  plastic 
  on 
  grinding 
  and 
  mixing 
  with 
  

   water, 
  whereas 
  no 
  amount 
  of 
  grinding 
  renders 
  the 
  flint 
  clays 
  more 
  

   than 
  very 
  slightly 
  plastic. 
  The 
  latter 
  are 
  not 
  found 
  in 
  Xew 
  York 
  

   state, 
  but 
  occur 
  abundantly 
  in 
  Pennsylvania, 
  Ohio, 
  Kentucky, 
  

   Missouri 
  and 
  one 
  or 
  two 
  other 
  states. 
  

  

  In 
  chemical 
  composition 
  the 
  flint 
  clays 
  stand 
  close 
  to 
  kaolinite, 
  

   and 
  at 
  times 
  even 
  exceed 
  it 
  in 
  the 
  percentage 
  of 
  alumina 
  which 
  

   they 
  contain. 
  (See 
  Kaolin, 
  p. 
  503.) 
  Flint 
  clays 
  vary 
  in 
  color, 
  

   being 
  gray, 
  black, 
  brown 
  or 
  even 
  yellowish. 
  The 
  iron 
  contents 
  

   of 
  the 
  bed 
  are 
  generally 
  collected 
  in 
  concretionary 
  masses. 
  In 
  

  

  