﻿62 
  

  

  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  cross 
  the 
  east 
  and 
  west 
  section 
  which 
  he 
  gives. 
  During 
  all 
  the 
  

   writer's 
  experience 
  the 
  mine 
  has 
  been 
  full 
  of 
  water. 
  

  

  Diamond 
  drill 
  cores 
  on 
  the 
  surface 
  near 
  the 
  Lee 
  pit 
  indicate 
  

   another 
  dike 
  in 
  its 
  northern 
  extension 
  and 
  observations 
  on 
  the 
  

   surface 
  show 
  it 
  to 
  be 
  a 
  large 
  one. 
  It 
  can 
  be 
  traced 
  for 
  a 
  quarter 
  

   of 
  a 
  mile 
  to 
  the 
  northeast. 
  

  

  In 
  this 
  district 
  the 
  dikes 
  have 
  not 
  shown 
  more 
  than 
  4 
  or 
  5 
  feet 
  of 
  

   section 
  in 
  the 
  mines. 
  They 
  are 
  likely 
  to 
  appear 
  at 
  almost 
  any 
  

   moment 
  and 
  they 
  may 
  be 
  associated 
  with 
  small 
  faults, 
  but 
  they 
  

   need 
  never 
  cause 
  anxiety 
  beyond 
  this 
  possibility. 
  

  

  Dark 
  basic 
  gabbros. 
  These 
  rocks 
  are 
  widespread 
  and 
  yet 
  in 
  

   less 
  areal 
  extent 
  than 
  the 
  others 
  whose 
  description 
  follows. 
  They 
  

   seem 
  to 
  appear 
  without 
  any 
  pronounced 
  structural 
  relationship, 
  

   but 
  to 
  have 
  welled 
  up 
  as 
  the 
  last 
  large 
  product 
  of 
  the 
  great 
  igneous 
  

   activity. 
  The 
  diabase 
  dikes 
  are 
  so 
  much 
  smaller 
  that 
  they 
  are 
  not 
  

   considered 
  to 
  be 
  of 
  the 
  same 
  order 
  of 
  magnitude. 
  The 
  gabbros 
  

   are 
  dark 
  green 
  or 
  black 
  in 
  color 
  and 
  have, 
  when 
  closely 
  examined, 
  

   a 
  faint 
  pinkish 
  cast 
  from 
  the 
  quite 
  invariable 
  and 
  richly 
  dissemi- 
  

   nated 
  small 
  garnets, 
  which 
  are 
  general 
  throughout 
  the 
  mass 
  in 
  

   the 
  form 
  of 
  rims 
  around 
  the 
  dark 
  silicates 
  and 
  iron 
  ores. 
  The 
  

   chief 
  component 
  minerals 
  are 
  a 
  dark 
  green 
  plagioclase, 
  in 
  rudely 
  

   tabular 
  crystals, 
  so 
  thickly 
  charged 
  with 
  dust 
  of 
  pyroxene 
  and 
  

   spinel 
  as 
  to 
  be 
  at 
  the 
  best 
  translucent 
  in 
  the 
  slides; 
  augite, 
  which 
  

   is 
  black 
  in 
  the 
  hand 
  specimen 
  and 
  green 
  in 
  the 
  slide; 
  hypersthene 
  

   of 
  variable 
  though 
  sometimes 
  large 
  amount; 
  brown 
  hornblende 
  in 
  

   the 
  same 
  relations; 
  and 
  very 
  abundant 
  and 
  sometimes 
  relatively 
  

   large 
  bits 
  of 
  titaniferous 
  magnetite. 
  The 
  feldspars 
  on 
  the 
  one 
  hand 
  

   and 
  the 
  dark 
  silicates 
  and 
  ores 
  on 
  the 
  other 
  almost 
  never 
  come 
  

   into 
  actual 
  contact, 
  but 
  are 
  separated 
  by 
  the 
  rims 
  of 
  garnet 
  referred 
  

   to 
  above, 
  which 
  course 
  through 
  the 
  rock 
  in 
  faint 
  pink 
  bands. 
  

  

  The 
  gabbros 
  almost 
  always 
  show 
  some 
  gneissoid 
  foliation. 
  In 
  

   extreme 
  cases 
  they 
  pass 
  into 
  hornblende 
  schists 
  or 
  amphibolites. 
  

   In 
  large 
  part 
  the 
  change 
  is 
  probably 
  due 
  to 
  dynamic 
  shearing 
  

   and 
  dragging, 
  but 
  the 
  banded 
  alinement 
  of 
  the 
  minerals 
  may 
  be 
  

   in 
  part 
  attributable 
  to 
  original 
  flow 
  structures. 
  The 
  gabbros 
  

   assume 
  the 
  form 
  of 
  intrusive 
  sheets 
  and 
  irregular 
  masses, 
  whose 
  

   outlines 
  can 
  seldom 
  be 
  worked 
  out 
  sharply 
  because 
  of 
  lack 
  of 
  

   exposures. 
  The 
  railway 
  cuts 
  along 
  Lake 
  Champlain 
  show 
  that 
  the 
  

   intrusive 
  mass 
  may 
  tongue 
  out 
  into 
  the 
  Grenville 
  limestone 
  with 
  

   all 
  manner 
  of 
  apophyses. 
  Elsewhere 
  single 
  dikes 
  are 
  known, 
  

   although 
  they 
  are 
  not 
  sharply 
  defined 
  anywhere 
  within 
  the 
  area 
  

   under 
  discussion. 
  In 
  the 
  maximum, 
  the 
  gabbros 
  may 
  cover 
  as 
  

  

  