﻿j520 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  there 
  were 
  three 
  times 
  as 
  mucli 
  lime 
  tO' 
  destroy 
  the 
  red 
  color, 
  but 
  

   even 
  then 
  the 
  resulting 
  tint 
  would 
  be 
  yellowish. 
  Even 
  a 
  very 
  small 
  

   amount, 
  below 
  1^, 
  may 
  produce 
  a 
  grayish 
  tint 
  at 
  high 
  temperatures. 
  

  

  Brick 
  clays 
  should 
  contain 
  sufficient 
  iron 
  to 
  give 
  a 
  good 
  red 
  color, 
  

   provided 
  that 
  is 
  desired 
  in 
  the 
  product. 
  

  

  For 
  fire 
  clays 
  a 
  small 
  iron 
  percentage 
  is 
  desirable, 
  in 
  fact 
  the 
  

   total 
  of 
  fluxes 
  should 
  be 
  low, 
  and 
  in 
  every 
  case 
  the 
  permissible 
  

   quantity 
  of 
  iron, 
  so 
  far 
  as 
  its 
  fluxing 
  effect 
  is 
  concerned, 
  depends 
  on 
  

   the 
  relative 
  amounts 
  of 
  the 
  other 
  fluxes 
  contained 
  in 
  the 
  clay. 
  

  

  The 
  following 
  is 
  the 
  range 
  of 
  ferric 
  oxid 
  contained 
  in 
  a 
  number 
  

   of 
  clays. 
  

  

  Kiud 
  of 
  clay 
  Max. 
  Min, 
  Aver. 
  

  

  Brick 
  clays 
  32.12 
  .126 
  5.311 
  

  

  Fireclays 
  .01 
  7.24 
  1.506 
  

  

  Kaolins 
  tr 
  6.87 
  1.29 
  

  

  Lime 
  

  

  Lime 
  is 
  a 
  very 
  common 
  impurity 
  of 
  many 
  clays, 
  specially 
  of 
  low 
  

   grade 
  ones. 
  

  

  A 
  large 
  number 
  of 
  minerals 
  may 
  serve 
  as 
  its 
  source, 
  but 
  in 
  all 
  

   of 
  these 
  it 
  is 
  present 
  in 
  one 
  of 
  three 
  conditions. 
  

  

  1 
  As 
  a 
  silicate 
  in 
  certain 
  feldspars, 
  hornblende, 
  garnet 
  

  

  2 
  As 
  a 
  carbonate, 
  limestone 
  or 
  calcite, 
  dolomite 
  

  

  3 
  As 
  a 
  sulfate 
  in 
  gypsum 
  

  

  The 
  first 
  two 
  classes 
  include 
  primary 
  mineral 
  constituents 
  of 
  

   clays, 
  but 
  the 
  third, 
  gypsum, 
  is 
  most 
  commonly 
  of 
  secondary 
  origi^n, 
  

   having 
  resulted 
  from 
  chemical 
  action 
  Avithin 
  the 
  clay. 
  

  

  In 
  many 
  clays, 
  lime 
  probably 
  occurs 
  as 
  a 
  constituent 
  of 
  some 
  

   silicate 
  mineral, 
  a 
  lime 
  soda 
  feldspar, 
  hornblende 
  or 
  garnet. 
  This 
  

   would 
  be 
  the 
  case 
  if 
  the 
  clay 
  was 
  derived 
  from 
  an 
  igneous 
  or 
  meta- 
  

   jnorphic 
  rock. 
  There 
  are 
  other 
  silicates 
  containing 
  lime, 
  but 
  their 
  

   presence 
  in 
  clay 
  is 
  probably 
  not 
  very 
  frequent. 
  Lime 
  when 
  present 
  

   in 
  a 
  silicate 
  acts 
  as 
  a 
  flux, 
  but 
  is 
  seldom 
  liable 
  to 
  exert 
  a 
  decolorizing 
  

  

  