﻿LAURENTIAN 
  LIMESTONES 
  OF 
  NORTH 
  AMERICA. 
  89 
  

  

  while 
  in 
  St. 
  Lawrence 
  count} 
  7 
  the 
  red 
  hematite 
  predominates, 
  and 
  

   forms 
  very 
  extensive 
  deposits. 
  In 
  Beverley 
  and 
  in 
  Bastard, 
  Onta- 
  

   rio, 
  small 
  beds 
  of 
  this 
  ore 
  occur 
  in 
  the 
  Potsdam 
  sandstone, 
  which 
  

   there 
  rests 
  directly 
  on 
  the 
  Laurentian,' 
  and 
  some 
  of 
  the 
  other 
  

   deposits 
  of 
  red 
  hematite, 
  already 
  alluded 
  to, 
  may 
  perhaps 
  be 
  

   found 
  to 
  rest 
  upon 
  this 
  ancient 
  system 
  instead 
  of 
  forming 
  part 
  

   of 
  it. 
  

  

  The 
  magnetic 
  and 
  hematitic 
  iron 
  ores 
  are 
  sometimes 
  intimately 
  

   associated 
  both 
  in 
  Scandinavia 
  and 
  in 
  Canada. 
  A 
  specimen 
  now 
  

   before 
  me 
  from 
  the 
  great 
  magnetic 
  ore 
  bed 
  in 
  Hull, 
  Quebec, 
  con- 
  

   sists 
  of 
  two 
  parallel 
  layers, 
  each 
  about 
  an 
  inch 
  thick, 
  the 
  one 
  of 
  

   coarsely 
  granular 
  magnetite, 
  and 
  the 
  other 
  of 
  compact 
  red 
  hema- 
  

   tite, 
  not 
  at 
  all 
  magnetic, 
  the 
  two 
  being 
  somewhat 
  intermingled 
  for 
  

   half 
  an 
  inch 
  at 
  the 
  junction. 
  : 
  Grains 
  of 
  greenish 
  feldspar 
  are 
  dis- 
  

   seminated 
  in 
  the 
  magnetite, 
  and 
  both 
  it 
  and 
  the 
  hematite 
  contain 
  

   imbedded 
  crystalline 
  plates 
  of 
  graphite 
  a 
  tenth 
  of 
  an 
  inch 
  or 
  more 
  

   in 
  diameter. 
  A 
  film 
  of 
  scaly 
  graphite, 
  moreover, 
  coats 
  the 
  free 
  

   surface 
  of 
  the 
  hematite 
  layer. 
  

  

  Franklinite, 
  Zincite. 
  — 
  The 
  two 
  remarkable 
  ores, 
  which 
  are 
  

   found 
  together 
  in 
  Sterling 
  and 
  Franklin, 
  New 
  Jersev, 
  were 
  loner 
  

   since 
  described 
  by 
  Prof. 
  H. 
  D. 
  Rogers 
  as 
  occurring 
  in 
  veins 
  which 
  

   traverse 
  the 
  crystalline 
  limestone 
  of 
  the 
  region 
  {Final 
  Report, 
  

   Geol. 
  JST. 
  Jersey, 
  1840, 
  pages 
  63, 
  64 
  and 
  69-71). 
  The 
  red 
  oxyd 
  

   or 
  zincite 
  sometimes 
  forms 
  the 
  gangue 
  of 
  the 
  franklinite 
  ; 
  at 
  other 
  

   times 
  the 
  two 
  ores 
  are 
  associated 
  in 
  a 
  matrix 
  of 
  calcite, 
  whose 
  

   peculiar 
  composition 
  has 
  already 
  been 
  noticed 
  under 
  its 
  proper 
  

   head. 
  The 
  silicate 
  of 
  zinc, 
  willemite, 
  is 
  also 
  occasionally 
  found 
  

   with 
  the 
  franklinite 
  in 
  the 
  calcareous 
  veinstone. 
  It 
  remains 
  to 
  be 
  

   seen 
  whether 
  these 
  ores 
  do 
  not, 
  like 
  the 
  magnetite, 
  occur 
  in 
  the 
  

   stratified 
  rocks 
  of 
  the 
  region. 
  These 
  zinciferous 
  minerals 
  appear 
  

   to 
  be 
  confined 
  to 
  a 
  small 
  area 
  in 
  New 
  Jersey, 
  as 
  they 
  have 
  never 
  

   yet 
  been 
  seen 
  elsewhere 
  in 
  the 
  Laurentian 
  rocks 
  of 
  North 
  America 
  

   or 
  of 
  Scandinavia. 
  They 
  are 
  sometimes 
  accompanied 
  by 
  colorless 
  

   transparent 
  blende. 
  

  

  Iron 
  Pyrites. 
  — 
  Cubic 
  iron 
  pyrites 
  is 
  of 
  not 
  unfrequent 
  occur- 
  

   rence 
  in 
  the 
  calcareous 
  Laurentian 
  veins, 
  sometimes 
  in 
  distinct 
  

   crystals, 
  imbedded 
  in 
  calcite, 
  and 
  at 
  other 
  times 
  filling 
  up 
  con- 
  

   siderable 
  portions 
  of 
  the 
  veins, 
  as 
  in 
  some 
  localities 
  in 
  Burgess, 
  

   and 
  associated 
  with 
  apatite, 
  pyroxene 
  or 
  mica. 
  In 
  an 
  instance 
  

  

  