﻿ADIRONDACK 
  MAGNETIC 
  IRON 
  ORES 
  49 
  

  

  and 
  shearing 
  movements 
  have 
  occurred. 
  The 
  Knob 
  mountain 
  

   granite, 
  the 
  syenite 
  and 
  the 
  gabbro 
  are 
  frequently 
  gneissoid, 
  it 
  is 
  

   true, 
  but 
  they 
  preserve 
  recognizable 
  textural 
  characters 
  that 
  leave 
  

   no 
  doubt 
  as 
  to 
  their 
  relationships. 
  It 
  seems 
  likely, 
  therefore, 
  that 
  

   the 
  gneiss 
  has 
  suffered 
  greater 
  vicissitudes 
  from 
  compression 
  and 
  

   other 
  dynamic 
  influences 
  than 
  the 
  igneous 
  rocks 
  due 
  to 
  an 
  earlier 
  

   period 
  of 
  formation. 
  No 
  apophyses 
  or 
  masses 
  of 
  the 
  gneiss 
  

   approaching 
  dike 
  form 
  have 
  been 
  found 
  in 
  the 
  adjacent 
  sediment- 
  

   ary 
  series 
  and 
  contact 
  effects 
  are 
  wanting. 
  On 
  the 
  other 
  hand 
  the 
  

   gneiss 
  is 
  involved 
  with 
  the 
  hornblende 
  gneiss 
  in 
  a 
  way 
  that 
  is 
  

   difficult 
  to 
  explain 
  on 
  the 
  theory 
  that 
  the 
  former 
  has 
  been 
  intruded 
  

   into 
  the 
  latter. 
  Alternating 
  bands 
  of 
  the 
  two 
  rocks 
  occur 
  along 
  

   the 
  borders 
  of 
  the 
  areas. 
  This 
  feature 
  is 
  particularly 
  well 
  devel- 
  

   oped 
  south 
  of 
  Hammondville 
  in 
  Burnt 
  Mill 
  valley, 
  where 
  the 
  bands 
  

   of 
  hornblende 
  gneiss 
  may 
  be 
  observed 
  more 
  frequently 
  as 
  the 
  con- 
  

   tact 
  is 
  approached. 
  The 
  regularity 
  in 
  width 
  of 
  the 
  bands, 
  their 
  

   perfect 
  conformity 
  to 
  the 
  strike 
  and 
  their 
  persistency 
  suggest 
  

   interbedding 
  rather 
  than 
  inclusions 
  caught 
  up 
  by 
  an 
  invading 
  

   igneous 
  magma. 
  If 
  the 
  view 
  that 
  the 
  gneiss 
  is 
  not 
  an 
  intrusive 
  be 
  

   accepted, 
  then 
  the 
  rock 
  probably 
  belongs 
  in 
  the 
  sedimentary 
  

   series. 
  The 
  alternative 
  that 
  it 
  may 
  represent 
  a 
  part 
  of 
  the 
  basal 
  

   complex 
  on 
  which 
  the 
  latter 
  have 
  been 
  laid 
  down 
  has 
  little 
  claim 
  

   to 
  attention 
  since 
  on 
  this 
  theory 
  the 
  same 
  difficulties 
  would 
  arise 
  

   in 
  explaining 
  the 
  contact 
  relations 
  with 
  the 
  sediments 
  that 
  are 
  

   met 
  by 
  the 
  intrusive 
  theory. 
  The 
  existence 
  of 
  a 
  fundamental 
  

   system 
  of 
  rocks 
  underlying 
  the 
  limestones 
  anyway 
  has 
  not 
  been 
  

   established 
  beyond 
  peradventure 
  in 
  the 
  Adirondack 
  region. 
  

  

  The 
  structural 
  relations 
  of 
  the 
  gneiss 
  are 
  very 
  obscure. 
  Satis- 
  

   factory 
  readings 
  of 
  dips 
  and 
  strikes 
  are 
  not 
  obtainable 
  over 
  much 
  

   of 
  the 
  area, 
  owing 
  to 
  absence 
  of 
  those 
  minerals 
  which 
  produce 
  

   foliation. 
  That 
  the 
  rock 
  has 
  been 
  subjected 
  to 
  intense 
  plication 
  

   is 
  evidenced 
  by 
  the 
  included 
  pegmatite 
  bands, 
  which 
  are 
  folded 
  

   and 
  twisted 
  in 
  the 
  most 
  intricate 
  manner, 
  as 
  well 
  as 
  by 
  the 
  struct- 
  

   ure 
  of 
  the 
  ore 
  bodies 
  hereafter 
  described. 
  The 
  observations 
  of 
  

   dips 
  and 
  strikes 
  where 
  made 
  point 
  to 
  a 
  concordant 
  arrangement 
  of 
  

   the 
  ore-bearing 
  gneiss 
  and 
  the 
  sedimentary 
  rocks. 
  The 
  latter 
  as 
  a 
  

   rule 
  show 
  strikes 
  that 
  follow 
  more 
  or 
  less 
  closely 
  the 
  outline 
  of 
  the 
  

   area, 
  suggesting 
  that 
  they 
  wrap 
  around 
  and 
  overlie 
  the 
  gneiss, 
  

   though 
  their 
  inclination 
  seems 
  to 
  be 
  quite 
  irregular. 
  The 
  attitude 
  

   of 
  the 
  whole 
  series 
  may 
  be 
  the 
  result 
  of 
  a 
  compressed 
  anticlinal 
  

   fold. 
  

  

  If 
  originally 
  a 
  sediment 
  the 
  ore-bearing 
  gneiss 
  has 
  probably 
  been 
  

  

  