﻿30 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Essex 
  county, 
  notably 
  around 
  Crown 
  Point. 
  Compared 
  with 
  the 
  

   preceding 
  group 
  the 
  most 
  striking 
  peculiarity 
  of 
  these 
  magnetites 
  

   is 
  the 
  constant 
  association 
  of 
  pyrite 
  which 
  brings 
  the 
  sulfur 
  content 
  

   up 
  to 
  very 
  considerable 
  amounts, 
  a 
  feature 
  that 
  has 
  been 
  a 
  serious 
  

   handicap 
  to 
  their 
  development 
  in 
  the 
  past. 
  The 
  pyrite 
  may 
  

   possibly 
  be 
  traceable 
  to 
  original 
  organic 
  matter 
  in 
  the 
  sandstones, 
  

   limestones 
  and 
  shales 
  from 
  which 
  the 
  present 
  rocks 
  have 
  probably 
  

   been 
  derived. 
  The 
  widespread 
  occurrence 
  of 
  graphite 
  in 
  the 
  same 
  

   rocks 
  is 
  noticeable. 
  

  

  At 
  Benson 
  Mines, 
  St 
  Lawrence 
  county, 
  the 
  ore 
  body 
  consists 
  of 
  

   an 
  impregnated 
  zone 
  in 
  a 
  quart 
  zose 
  banded 
  gneiss. 
  The 
  gneiss 
  con- 
  

   tains 
  sillimanite 
  and 
  scapolite 
  in 
  addition 
  to 
  the 
  feldspar, 
  while 
  the 
  

   dark 
  minerals 
  include 
  hornblende, 
  biotite 
  and 
  augite. 
  Garnet 
  and 
  

   pyrite 
  are 
  prominent. 
  The 
  walls 
  in 
  places 
  are 
  cut 
  by 
  a 
  later 
  horn- 
  

   blende 
  granite. 
  

  

  The 
  Clifton 
  mines, 
  north 
  of 
  Benson, 
  and 
  those 
  on 
  Vrooman 
  ridge, 
  

   near 
  Fine, 
  are 
  found 
  within 
  a 
  black 
  hornblende 
  schist 
  with 
  inter- 
  

   bedded 
  layers 
  of 
  impure 
  crystalline 
  limestone. 
  The 
  latter 
  occurs 
  

   next 
  to 
  the 
  ore 
  in 
  one 
  of 
  the 
  openings 
  at 
  Clifton. 
  

  

  At 
  Jayville 
  the 
  same 
  sedimentary 
  series 
  is 
  in 
  evidence, 
  though 
  

   here 
  the 
  ore 
  bodies 
  and 
  walls 
  (hornblende-biotite 
  schist) 
  have 
  been 
  

   invaded 
  by 
  a 
  great 
  granite 
  mass 
  which 
  has 
  broken 
  up 
  what 
  was 
  

   apparently 
  a 
  continuous 
  bed 
  into 
  numerous 
  lenses 
  and 
  shoots 
  that 
  

   seem 
  to 
  give 
  out 
  in 
  depth 
  after 
  passing 
  the 
  limits 
  of 
  the 
  schist. 
  

   Curiously 
  enough, 
  the 
  ore 
  contains 
  little 
  pyrite. 
  There 
  is 
  evidence 
  

   of 
  recrystallization 
  of 
  the 
  magnetite, 
  and 
  contact 
  action 
  has 
  

   caused 
  the 
  formation 
  of 
  great 
  masses 
  of 
  hornblende 
  and 
  abundant 
  

   titanite. 
  

  

  The 
  several 
  mines 
  near 
  Crown 
  Point 
  have 
  opened 
  on 
  bands 
  of 
  

   pyritous 
  magnetite 
  which 
  are 
  inclosed 
  by 
  a 
  black 
  hornblende 
  gneiss 
  

   that 
  has 
  been 
  correlated 
  with 
  the 
  Grenville 
  of 
  this 
  section. 
  The 
  

   gneiss 
  has 
  been 
  intruded 
  by 
  granite 
  and 
  in 
  some 
  places 
  the 
  latter 
  

   lies 
  close 
  to 
  the 
  ore. 
  The 
  ore 
  bodies 
  are 
  parallel 
  in 
  all 
  respects 
  to 
  

   the 
  St 
  Lawrence 
  county 
  deposits. 
  

  

  Origin 
  of 
  the 
  magnetites 
  

  

  The 
  origin 
  of 
  these 
  ore 
  bodies 
  has 
  been 
  variously 
  interpreted 
  by 
  

   geologists. 
  The 
  problem 
  is 
  an 
  obscure 
  one, 
  involving 
  as 
  it 
  does 
  

   accumulations 
  of 
  ores 
  in 
  rocks 
  which 
  are 
  among 
  the 
  most 
  ancient 
  

   known 
  on 
  the 
  earth's 
  surface 
  and 
  which 
  in 
  many 
  cases 
  have 
  under- 
  

   gone 
  great 
  vicissitudes 
  from 
  compression 
  and 
  metamorphism. 
  So 
  

  

  