﻿508 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  coarsely 
  crystalline 
  ground 
  mass 
  of 
  biotite 
  and 
  gray 
  or 
  green 
  or- 
  

   thoelase, 
  plagioclaee, 
  quartz, 
  magnetite 
  and 
  a 
  little 
  pyrite. 
  

  

  Elsewhere 
  we 
  have 
  often 
  met 
  augen-gneisses 
  of 
  this 
  mineral- 
  

   ogy, 
  or 
  with 
  more 
  or 
  less 
  quartz 
  than 
  the 
  type, 
  and 
  we 
  have 
  been 
  

   at 
  a 
  loss 
  to 
  account 
  for 
  them. 
  The 
  hill 
  at 
  Horicon 
  has 
  been 
  

   quarried 
  in 
  some 
  places 
  for 
  a 
  massive 
  granite, 
  but 
  to 
  the 
  north 
  

   the 
  massive 
  rock 
  passes 
  over 
  into 
  an 
  augen-gneiss. 
  There 
  is 
  ex- 
  

   cellent 
  ground 
  for 
  referring 
  therefore 
  many 
  augen-gneisses 
  else- 
  

   where, 
  to 
  an 
  original 
  porphyritic 
  eruptive 
  of 
  this 
  character. 
  The 
  

   rock 
  is 
  called 
  in 
  the 
  following 
  pages 
  the 
  " 
  Horicon 
  type." 
  

  

  4 
  We 
  have 
  also 
  discovered, 
  and 
  specially 
  around 
  Whitehall, 
  

   excessively 
  or 
  purely 
  quartzose 
  gneisses 
  or 
  foliated 
  quartzites 
  

   that 
  are 
  quite 
  certainly 
  metamorphosed 
  sediments. 
  They 
  form 
  

   notable 
  areas 
  along 
  the 
  head 
  of 
  South 
  bay, 
  Whitehall 
  township, 
  

   and 
  will 
  be 
  called 
  the 
  " 
  South 
  Bay 
  type." 
  Some 
  feldspar 
  is 
  

   present, 
  and 
  more 
  or 
  less 
  garnet, 
  but 
  the 
  quartz 
  is 
  far 
  in 
  excess 
  

   of 
  any 
  possible 
  igneous 
  rock, 
  except 
  a 
  pegmatite 
  that 
  is 
  almost 
  

   a 
  quartz 
  vein. 
  The 
  exposures 
  are 
  too 
  large 
  for 
  a 
  pegmatite 
  and 
  

   they 
  are 
  associated 
  with 
  crystalline 
  limestone. 
  They 
  are 
  similar 
  

   to 
  the 
  rocks 
  described 
  as 
  quartzites 
  by 
  Dr 
  F. 
  D. 
  Adams 
  from 
  the 
  

   Laurentian 
  areas 
  of 
  Quebec, 
  as 
  is 
  shown 
  by 
  a 
  comparison 
  of 
  

   specimens. 
  These 
  rocks 
  have 
  been 
  elsewhere 
  noted 
  by 
  the 
  senior 
  

   writer, 
  in 
  association 
  with 
  the 
  crystalline 
  limestones. 
  There 
  is 
  

   also 
  the 
  peculiar 
  graphitic 
  quartzite 
  at 
  the 
  graphite 
  mines 
  near 
  

   Hague, 
  Warren 
  co. 
  that 
  must 
  be 
  noted 
  as 
  an 
  additional 
  Pre- 
  

   cambrian 
  quartzite, 
  of 
  the 
  highest 
  stratigraphic 
  significance.® 
  It 
  

   is 
  fully 
  described 
  on 
  a 
  subsequent 
  page, 
  but 
  we 
  may 
  note 
  here 
  

   also, 
  the 
  sillimanite-garnet 
  gneiss, 
  that 
  lies 
  over 
  and 
  under 
  the 
  

   graphitic 
  quartzite 
  as 
  a 
  rock 
  not 
  observed 
  as 
  yet 
  in 
  any 
  other 
  

   part 
  of 
  the 
  mountains. 
  We 
  have 
  been 
  led 
  by 
  these 
  exposures 
  

   to 
  a 
  strengthened 
  belief 
  in 
  the 
  former 
  presence 
  of 
  a 
  great 
  series 
  

   of 
  sedimentary 
  rocks, 
  which 
  had 
  been 
  already 
  indicated 
  by 
  the 
  

   crystalline 
  limestones, 
  but 
  in 
  which 
  from 
  previous 
  work 
  we 
  had 
  

   seldom 
  noted 
  well-marked 
  fragmental 
  sediments. 
  We 
  are 
  hope- 
  

  

  a 
  See 
  C. 
  D. 
  Walcott. 
  Bull. 
  Geol. 
  soc. 
  Amer. 
  10:227, 
  pi. 
  22. 
  This 
  note 
  appeared 
  after 
  the 
  

   present 
  report 
  was 
  sent 
  in. 
  

  

  