﻿46 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  granitic 
  rocks. 
  The 
  texture 
  gives 
  no 
  clue 
  to 
  its 
  original 
  nature, 
  

   being 
  completely 
  granulated 
  in 
  most 
  specimens. 
  The 
  quartz 
  

   particles 
  seem 
  to 
  be 
  an 
  earlier 
  crystallization 
  than 
  the 
  feldspar, 
  

   contrary 
  to 
  the 
  usual 
  order 
  of 
  igneous 
  rocks. 
  

  

  Sedimentary 
  crystallines. 
  The 
  principal 
  members 
  of 
  the 
  sedi- 
  

   mentary 
  or 
  Grenville 
  series 
  are 
  limestone, 
  hornblende 
  gneiss 
  and 
  

   mica 
  schist. 
  Dr 
  Ogilvie 
  has 
  recorded 
  the 
  presence 
  of 
  quart 
  zite 
  

   and 
  sillimanite 
  gneiss 
  in 
  the 
  upper 
  part 
  of 
  the 
  series, 
  but 
  they 
  have 
  

   no 
  representation 
  within 
  the 
  limits 
  of 
  the 
  district. 
  The 
  sedimen- 
  

   tary 
  derivatives 
  are 
  closely 
  associated 
  in 
  their 
  field 
  relations. 
  

  

  The 
  limestone 
  forms 
  bands 
  and 
  larger 
  belts 
  that 
  are 
  followed 
  by 
  

   the 
  stream 
  courses. 
  It 
  is 
  thoroughly 
  crystalline 
  and 
  frequently 
  

   contains 
  such 
  minerals 
  as 
  graphite, 
  pyroxene, 
  amphibole 
  and 
  

   phlogopite 
  and 
  other 
  silicates 
  that 
  have 
  originated 
  from 
  the. 
  

   alteration 
  of 
  the 
  limestone 
  and 
  its 
  impurities 
  by 
  metamorphic 
  

   agencies. 
  

  

  The 
  hornblendic 
  and 
  micaceous 
  gneisses 
  and 
  schists 
  though 
  

   completely 
  changed 
  from 
  their 
  original 
  condition 
  show 
  indubitable 
  

   evidences 
  of 
  their 
  sedimentary 
  derivation. 
  They 
  are 
  as 
  a 
  rule 
  

   very 
  quart 
  zose, 
  with 
  a 
  proportionately 
  small 
  amount 
  of 
  feldspar 
  

   and 
  varying 
  quantities 
  of 
  hornblende 
  and 
  mica. 
  They 
  are 
  con- 
  

   spicuously 
  banded; 
  beds 
  of 
  light 
  and 
  dark 
  varieties 
  alternate 
  

   across 
  the 
  strike, 
  their 
  junctions 
  being 
  sharp 
  like 
  the 
  planes 
  sepa- 
  

   rating 
  different 
  sedimentary 
  beds. 
  Garnet, 
  pyrite 
  and 
  occasionally 
  

   graphite 
  occur 
  as 
  accessory 
  minerals. 
  

  

  Intrusive 
  rocks. 
  Of 
  the 
  recognizable 
  intrusives 
  found 
  in 
  the 
  

   Hammondville 
  district, 
  the 
  anorthosite 
  and 
  gabbro 
  are 
  uniform 
  

   in 
  their 
  geology 
  and 
  mineral 
  character 
  with 
  the 
  general 
  types 
  

   which 
  constitute 
  the 
  central 
  Adirondacks. 
  They 
  grade 
  into 
  each 
  

   other 
  by 
  imperceptible 
  stages 
  and 
  have 
  no 
  doubt 
  originated 
  from 
  

   a 
  common 
  magma. 
  The 
  syenite 
  may 
  also 
  belong 
  to 
  the 
  same 
  

   intrusive 
  series, 
  representing 
  a 
  more 
  acidic 
  development. 
  It 
  is 
  

   made 
  up 
  of 
  microperthite, 
  hornblende 
  and 
  a 
  green 
  augite, 
  but 
  in 
  

   some 
  phases 
  contains 
  labradorite 
  feldspar 
  as 
  well 
  and 
  shows 
  a 
  

   gradation 
  toward 
  the 
  gabbro. 
  These 
  rocks 
  are 
  all 
  later 
  than 
  the 
  

   sedimentary 
  formations 
  which 
  are 
  invaded 
  by 
  them, 
  though 
  the 
  

   relations 
  can 
  be 
  determined 
  infrequently 
  by 
  contact 
  effects 
  owing 
  

   to 
  the 
  regional 
  metamorphism 
  that 
  has 
  taken 
  place 
  subsequent 
  to 
  

   their 
  intrusion. 
  

  

  The 
  granite 
  found 
  on 
  Knob 
  mountain 
  and 
  in 
  small 
  areas 
  within 
  

   the 
  gneisses 
  is 
  a 
  coarse 
  reddish 
  variety. 
  It 
  contains 
  microcline 
  as 
  

   the 
  principal 
  feldspar, 
  with 
  some 
  orthoclase 
  and 
  quartz, 
  horn- 
  

  

  