﻿ECONOMIC 
  GEOLOGY 
  186 
  

  

  SANDSTONE 
  

  

  Sandstone 
  consists 
  of 
  grains 
  of 
  sand 
  which 
  are 
  united 
  by 
  a 
  

   cement. 
  

  

  The 
  grains 
  may 
  be 
  of 
  varying 
  sizes, 
  from 
  almost 
  impalpable 
  

   dust 
  to 
  small 
  pebbles, 
  and 
  may 
  be 
  angular 
  or 
  more 
  or 
  less 
  rounded 
  

   in 
  form. 
  The 
  cementing 
  matter 
  also 
  may 
  vary 
  greatly 
  in 
  its 
  

   nature. 
  From 
  this 
  variation, 
  both 
  in 
  the 
  grains 
  and 
  in 
  the 
  

   cement, 
  there 
  is 
  an 
  almost 
  endless 
  gradation 
  in 
  the 
  kinds 
  of 
  sand- 
  

   stone. 
  

  

  Quartz 
  is 
  the 
  essential 
  constituent, 
  but 
  with 
  it 
  there 
  may 
  be 
  

   feldspar, 
  mica, 
  calcite, 
  pyrite, 
  glauconite, 
  clay 
  or 
  other 
  minerals, 
  

   and 
  rock 
  fragments 
  common 
  to 
  stone 
  of 
  sedimentary 
  origin. 
  

   These 
  accessory 
  materials 
  often 
  give 
  character 
  to 
  the 
  mass, 
  and 
  

   make 
  a 
  basis 
  for 
  a 
  division 
  into 
  feldspathic, 
  micaceous, 
  calcare- 
  

   ous 
  sandstones, 
  etc.. 
  as 
  one 
  or 
  another 
  of 
  them 
  predominates. 
  

  

  The 
  texture 
  of 
  the 
  mass 
  also 
  is 
  subject 
  to 
  a 
  wide 
  range 
  of 
  vari- 
  

   ation, 
  from 
  fine-grained, 
  almost 
  aphanitic, 
  to 
  pebbly 
  sandstone, 
  

   or 
  conglomerate, 
  or 
  a 
  brecciated 
  stone 
  in 
  which 
  the 
  component 
  

   parts 
  are 
  more 
  or 
  less 
  angular. 
  

  

  Some 
  of 
  the 
  brown 
  sandstones 
  of 
  the 
  Triassic 
  age, 
  quarried 
  

   near 
  Haverstraw, 
  are 
  such 
  conglomeratic 
  and 
  brecciated 
  sand- 
  

   stones. 
  Accordingly, 
  as 
  the 
  grains 
  are 
  small 
  or 
  large, 
  the 
  stone 
  

   is 
  said 
  to 
  be 
  fine-grained 
  or 
  coarse-grained. 
  

  

  The 
  variety 
  of 
  the 
  cementing 
  material 
  also 
  affords 
  a 
  basis 
  for 
  

   classification. 
  Silicious 
  sandstones 
  have 
  the 
  grains 
  bound 
  to- 
  

   gether 
  by 
  silica. 
  They 
  consist 
  almost 
  exclusively 
  of 
  quartz, 
  

   and 
  grade 
  into 
  quartzite. 
  The 
  ferruginous 
  varieties 
  have 
  for 
  

   their 
  cement 
  an 
  oxide 
  of 
  iron, 
  often 
  coating 
  the 
  grains 
  and 
  mak- 
  

   ing 
  a 
  considerable 
  percentage 
  of 
  the 
  whole. 
  The 
  iron 
  is 
  usually 
  

   present 
  as 
  ferric 
  oxide. 
  Calcareous 
  sandstones 
  are 
  marked 
  by 
  

   the 
  presence 
  of 
  carbonate 
  of 
  lime. 
  When 
  it 
  exceeds 
  the 
  quartz 
  

   in 
  amount, 
  the 
  sandstone 
  becomes 
  a 
  silicious 
  limestone. 
  In 
  the 
  

   argillaceous 
  varieties, 
  the 
  binding 
  material 
  is 
  a 
  clay, 
  or 
  an 
  im- 
  

   pure 
  kaolin. 
  

  

  The 
  cementing 
  material 
  determines 
  in 
  most 
  cases 
  the 
  color. 
  

   The 
  various 
  shades 
  of 
  red 
  and 
  yellow 
  depend 
  upon 
  the 
  iron 
  

  

  