﻿LIMESTONES 
  OP 
  NEW 
  YORK 
  AND 
  THEIR 
  ECONOMIC 
  VALUE 
  429 
  

  

  Albany 
  county 
  

  

  The 
  only 
  limestone 
  formations 
  in 
  this 
  county 
  are 
  the 
  Helderberg 
  

   and 
  the 
  Corniferous. 
  The 
  former 
  are 
  specially 
  conspicuous 
  as 
  

   they 
  form 
  the 
  Helderberg 
  escarpment 
  which 
  in 
  this 
  county 
  reaches 
  

   its 
  greatest 
  elevation. 
  

  

  Onondaga 
  limestone. 
  In 
  Albany 
  county 
  this 
  formation 
  appears 
  

   as 
  a 
  terrace 
  extending 
  along 
  the 
  foot 
  of 
  the 
  slopes 
  formed 
  by 
  the 
  

   Hamilton 
  shales. 
  In 
  the 
  northeastern 
  face 
  of 
  Helderberg 
  moun- 
  

   tain 
  the 
  outcrop 
  is 
  narrow 
  but 
  it 
  widens 
  to 
  the 
  westward 
  being 
  

   a 
  mile 
  and 
  a 
  half 
  at 
  Thompson's 
  lake, 
  and 
  after 
  narrowing 
  it 
  

   again 
  becomes 
  three 
  miles 
  wide 
  in 
  the 
  long 
  slopes 
  northwest 
  of 
  

   Berne. 
  The 
  formation 
  in 
  this 
  county 
  is 
  a 
  light 
  bluish 
  gray, 
  

   tough, 
  massive 
  limestone, 
  quite 
  pure 
  but 
  containing 
  lenses 
  of 
  

   chert. 
  The 
  chert 
  is 
  chiefly 
  abundant 
  in 
  the 
  lower 
  beds 
  of 
  the 
  for- 
  

   mation. 
  At 
  times 
  it 
  disappears 
  altogether 
  but 
  this 
  is 
  not 
  usual. 
  

   One 
  of 
  the 
  best 
  ledges 
  of 
  Onondaga 
  limestone 
  is 
  in 
  the 
  cliffs 
  near 
  

   Oniskethau 
  creek 
  at 
  Clarksville. 
  

  

  Helderberg 
  limestone. 
  This 
  reaches 
  a 
  large 
  development 
  in 
  Al- 
  

   bany 
  county 
  and 
  is 
  divisible 
  into 
  several 
  well 
  marked 
  members. 
  

   The 
  foremost 
  of 
  these 
  is 
  the 
  Becraft, 
  also 
  known 
  as 
  the 
  Scutella 
  

   limestone. 
  This 
  rock 
  is 
  of 
  light 
  color, 
  often 
  crystalline 
  and 
  full 
  

   of 
  fossils. 
  Its 
  average 
  thickness 
  in 
  Albany 
  co. 
  is 
  about 
  15 
  

   feet, 
  and 
  its 
  composition 
  may 
  be 
  inferred 
  from 
  an 
  analysis 
  given 
  

   of 
  the 
  same 
  bed 
  occurring 
  at 
  Rondout, 
  Ulster 
  co. 
  and 
  Hudson, 
  

   Columbia 
  co. 
  One 
  exposure 
  of 
  it 
  is 
  in 
  the 
  creek 
  bed 
  south 
  of 
  

   Callanans 
  Corners. 
  Underlying 
  the 
  Becraft 
  limestone 
  is 
  a 
  series 
  

   of 
  different 
  beds 
  of 
  very 
  impure, 
  highly 
  fossiliferous, 
  shaly 
  lime- 
  

   stone 
  gray 
  and 
  grayish 
  brown 
  in 
  color 
  and 
  probably 
  too 
  impure 
  for 
  

   any 
  use 
  except 
  building 
  or 
  road 
  making. 
  Their 
  thickness 
  averages 
  

   100 
  feet. 
  Underlying 
  these 
  however 
  comes 
  the 
  Pentamerus 
  

   limestone 
  which 
  is 
  an 
  important 
  member 
  of 
  the 
  Helderberg 
  for- 
  

   mation. 
  Its 
  escarpment 
  is 
  marked 
  by 
  lines 
  of 
  prominent 
  cliffs. 
  

   It 
  is 
  usually 
  cracked, 
  and 
  its 
  color 
  is 
  that 
  of 
  a 
  red, 
  bluish 
  gray 
  

   limestone 
  which 
  is 
  of 
  a 
  lighter 
  color 
  on 
  the 
  weather 
  surface. 
  

   The 
  beds 
  are 
  often 
  cut 
  by 
  vertical 
  joints 
  and 
  there 
  may 
  be 
  occa- 
  

   sional 
  layers 
  of 
  shale. 
  The 
  Pentamerus 
  limestone 
  in 
  Albany 
  

  

  