﻿CLAYS 
  OF 
  NEW 
  YORK 
  613 
  

  

  The 
  loess 
  forms 
  an 
  extensive 
  deposit 
  over 
  a 
  large 
  area, 
  not 
  of 
  

   great 
  thickness^ 
  whicli 
  extends 
  from 
  north 
  to 
  south 
  across 
  the 
  

   state 
  and 
  eastward 
  from 
  the 
  foothills. 
  It 
  is 
  generally 
  a 
  very 
  sandy 
  

   elay 
  with 
  little 
  plasticity. 
  Clays 
  of 
  similar 
  nature 
  to 
  the 
  loess 
  

   are 
  found 
  underlying 
  the 
  river 
  terraces 
  in 
  many 
  of 
  the 
  broader 
  

   valleys 
  such 
  as 
  those 
  of 
  the 
  Arkansas, 
  Grand 
  river, 
  etc. 
  

  

  The 
  Mesozoic 
  formations 
  extend 
  along 
  the 
  eastern 
  edge 
  of 
  the 
  

   Kocky 
  mountains, 
  and 
  also 
  occur 
  in 
  some 
  of 
  the 
  deeper 
  valleys 
  

   tributary 
  to 
  the 
  foothill 
  belt. 
  They 
  consist 
  of 
  a 
  great 
  series 
  of 
  

   interbedded 
  shales, 
  sandstones, 
  and 
  limestone 
  of 
  Jura-Trias 
  and 
  

   Cretaceous 
  age, 
  the 
  beds 
  being 
  tilted 
  at 
  a 
  high 
  angle. 
  The 
  Jura- 
  

   Trias 
  shales 
  have 
  not 
  been 
  utilized, 
  but 
  the 
  Cretaceous 
  which 
  over- 
  

   lie 
  them 
  have 
  and 
  the 
  Tertiary 
  or 
  Denver 
  beds, 
  which 
  carry 
  great 
  

   deposits 
  of 
  clay, 
  have 
  been 
  mined 
  near 
  Golden 
  and 
  Boulder. 
  

  

  Brick 
  clays. 
  All 
  of 
  the 
  common 
  brick 
  manufactured 
  in 
  Colorado 
  

   are 
  made 
  either 
  from 
  the 
  loess 
  or 
  the 
  river 
  clays 
  in 
  the 
  valleys. 
  

  

  Pressed 
  brick 
  clays. 
  The 
  Cretaceous 
  and 
  Tertiary 
  formations 
  of 
  

   Colorado 
  contain 
  an 
  abundance 
  of 
  clay 
  suitable 
  for 
  the 
  manufacture 
  

   of 
  pressed 
  brick. 
  They 
  are 
  mined 
  at 
  Golden, 
  Boulder, 
  and 
  La 
  

   Junta. 
  

  

  Fire 
  clays 
  and 
  pottery 
  clays. 
  These 
  two 
  grades 
  of 
  clays 
  occur 
  in 
  

   close 
  association 
  interbedded 
  with 
  the 
  Dakota 
  sandstones, 
  in 
  the 
  

   hogbacks 
  extending 
  along 
  the 
  eastern 
  edge 
  of 
  the 
  Rocky 
  mountains. 
  

   The 
  fire 
  clay 
  has 
  been 
  extensively 
  mined 
  at 
  Golden, 
  Parkdale, 
  and 
  

   more 
  recently 
  at 
  Delhi. 
  The 
  beds 
  range 
  in 
  thickne^ 
  from 
  4 
  to 
  

   18 
  feet. 
  

  

  Clay 
  products. 
  Common 
  bricks 
  are 
  manufactured 
  at 
  many 
  locali- 
  

   ties 
  in 
  the 
  state. 
  Pressed 
  brick 
  are 
  only 
  made 
  at 
  La 
  Junta, 
  Golden, 
  

   Boulder 
  and 
  Denver. 
  Paving 
  bricks 
  have 
  been 
  produced 
  in 
  small 
  

   quantities, 
  and 
  stoneware 
  and 
  sewer 
  pipe 
  have 
  also 
  been 
  produced 
  

   to 
  a 
  limited 
  extent. 
  The 
  most 
  important 
  clay 
  products 
  made 
  in 
  

   Colorado 
  are 
  refractory 
  wares, 
  such 
  as 
  fire 
  brick, 
  locomotive 
  

   blocks, 
  muffles, 
  scorifiers 
  and 
  crucibles. 
  This 
  is 
  naturally 
  one 
  of 
  

  

  