﻿I50 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  the 
  railroad, 
  2 
  miles 
  north 
  of 
  Saratoga. 
  This 
  dike 
  is 
  at 
  least 
  100 
  

   feet 
  wide 
  on 
  the 
  average, 
  and 
  seems 
  a 
  very 
  long 
  one. 
  Its 
  average 
  

   trend 
  is 
  N 
  20 
  ° 
  E 
  to 
  N 
  25 
  ° 
  E. 
  For 
  three 
  quarters 
  of 
  a 
  mile 
  south 
  

   of 
  the 
  quarry 
  it 
  can 
  be 
  followed 
  unbroken, 
  and 
  north 
  of 
  the 
  quarry 
  

   we 
  have 
  picked 
  it 
  up 
  so 
  repeatedly 
  when 
  crossing 
  its 
  probable 
  

   location 
  as 
  to 
  convince 
  ourselves 
  that 
  it 
  must 
  be 
  the 
  same 
  dike 
  

   throughout. 
  

  

  The 
  rock 
  is 
  an 
  ordinary 
  diabase, 
  an 
  augite-feldspar-magnetite 
  

   combination, 
  lacking 
  olivine. 
  It 
  shows 
  everywhere 
  considerable 
  

   alteration, 
  the 
  feldspars 
  much 
  kaolinized 
  and 
  the 
  augite 
  largely 
  

   changed 
  to 
  chlorite. 
  These 
  changes 
  do 
  not 
  seem, 
  however, 
  to 
  have 
  

   seriously 
  impaired 
  the 
  strength 
  and 
  toughness 
  of 
  the 
  rock 
  and 
  

   should 
  not, 
  in 
  our 
  opinion, 
  much 
  impair 
  its 
  value 
  as 
  a 
  road 
  rock, 
  

   for 
  which 
  purpose 
  it 
  has 
  been 
  chiefly 
  used. 
  Because 
  of 
  its 
  width 
  

   and 
  great 
  length 
  this 
  dike 
  is 
  capable 
  of 
  furnishing 
  a 
  large 
  supply 
  

   of 
  road 
  material. 
  Where 
  worked 
  it 
  is 
  at 
  low 
  altitude 
  and 
  adjacent 
  

   to 
  a 
  railroad. 
  Its 
  northern 
  extension 
  is 
  less 
  fortunately 
  situated 
  

   in 
  these 
  respects, 
  and 
  the 
  same 
  is 
  true 
  of 
  the 
  other 
  dikes 
  of 
  trap 
  

   in 
  the 
  Precambric. 
  But 
  since 
  the 
  demand 
  for 
  good 
  trap 
  for 
  road- 
  

   making 
  purposes 
  in 
  New 
  York 
  at 
  the 
  present 
  time 
  is 
  large, 
  and 
  

   the 
  supply 
  from 
  the 
  dikes 
  in 
  the 
  Adirondack 
  Precambric 
  is 
  the 
  

   only 
  available 
  source 
  in 
  the 
  State 
  outside 
  of 
  Rockland 
  county, 
  it 
  

   would 
  seem 
  as 
  if 
  there 
  was 
  opportunity 
  for 
  some 
  development 
  

   of 
  the 
  industry 
  in 
  the 
  Saratoga 
  region, 
  owing 
  to 
  the 
  unusual 
  

   length 
  and 
  width 
  of 
  the 
  dikes. 
  

  

  Dolomite. 
  Two 
  quarries 
  have 
  been 
  opened 
  in 
  the 
  upper 
  beds 
  of 
  

   the 
  Little 
  Falls 
  dolomite, 
  within 
  the 
  limits 
  of 
  the 
  two 
  quadrangles, 
  

   one 
  on 
  Maple 
  avenue 
  in 
  the 
  northern 
  edge 
  of 
  Saratoga 
  Springs, 
  

   and 
  the 
  other 
  a 
  mile 
  south 
  of 
  Wilton, 
  Schuylerville 
  quadrangle. 
  

   In 
  both 
  cases 
  the 
  quarries 
  are 
  in 
  the 
  upper, 
  light 
  colored, 
  coarsely 
  

   crystalline 
  beds 
  of 
  the 
  formation. 
  In 
  the 
  Maple 
  avenue 
  quarry 
  

   a 
  thickness 
  of 
  22 
  feet 
  of 
  massive 
  beds 
  is 
  exposed 
  with 
  a 
  dip 
  of 
  

   about 
  5° 
  to 
  the 
  southeast. 
  The 
  upper 
  bed 
  is 
  full 
  of 
  chert; 
  some 
  

   of 
  the 
  lower 
  beds 
  are 
  full 
  of 
  drusy 
  cavities 
  lined 
  with 
  dolomite 
  

   crystals 
  and 
  containing 
  crystals 
  of 
  clear, 
  transparent 
  quartz. 
  A 
  

   small 
  fault 
  is 
  well 
  shown 
  in 
  the 
  quarry 
  wall 
  which 
  is 
  of 
  interest 
  

   because 
  it 
  seems 
  very 
  old. 
  The 
  throw 
  is 
  only 
  2 
  feet, 
  but 
  a 
  strip 
  

   of 
  fault 
  breccia 
  about 
  6 
  inches 
  wide 
  was 
  produced, 
  which 
  was 
  

   subsequently 
  solidly 
  welded 
  up 
  by 
  deposit 
  of 
  calcite 
  from 
  cir- 
  

   culating 
  waters, 
  so 
  that 
  the 
  rock 
  is 
  as 
  strong 
  and 
  firm 
  as 
  it 
  is 
  any- 
  

   where 
  in 
  the 
  quarry. 
  The 
  quarry 
  is 
  worked 
  only 
  intermittently, 
  

  

  