﻿524 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  type," 
  some 
  streaks 
  of 
  feldspar 
  remain, 
  and 
  garnets 
  are 
  still 
  

   quite 
  thickly 
  disseminated 
  through 
  the 
  mass 
  but 
  about 
  80$ 
  of 
  

   the 
  slide 
  on 
  an 
  estimate 
  is 
  quartz. 
  The 
  quartz 
  is 
  granulated 
  and 
  

   is 
  strung 
  out 
  in 
  bands. 
  At 
  no. 
  54 
  graphite 
  is 
  not 
  infrequent 
  in 
  

   the 
  rock, 
  and 
  appears 
  as 
  shining 
  scales 
  parallel 
  with 
  the 
  foliation. 
  

   Very 
  small 
  crystals 
  of 
  the 
  manganese 
  epidote, 
  piedmontite 
  are 
  

   to 
  be 
  detected 
  which 
  are 
  very 
  pretty 
  objects 
  under 
  the 
  micro- 
  

   scope. 
  They 
  seldom 
  are 
  more 
  than 
  .1 
  mm 
  long 
  by 
  a 
  fourth 
  as 
  

   broad. 
  They 
  yield 
  the 
  striking 
  pleochroism 
  of 
  the 
  mineral 
  being 
  

   green 
  parallel 
  with 
  the 
  elongation 
  and 
  blue 
  or 
  pink 
  across 
  it. 
  

   The 
  optical 
  characters 
  are 
  those 
  of 
  piedmontite 
  rather 
  than 
  

   thulite, 
  the 
  greatest 
  axis 
  of 
  elasticity 
  lying 
  across 
  the 
  elongation, 
  

   the 
  least 
  along 
  it, 
  as 
  shown 
  by 
  the 
  gypsum 
  plate. 
  A 
  photomicro- 
  

   graph 
  of 
  this 
  rock 
  is 
  given 
  on 
  plate 
  5, 
  fig. 
  A. 
  It 
  has 
  garnets 
  

   running 
  in 
  lenticular 
  masses 
  across 
  the 
  field 
  and 
  indicates 
  the 
  

   pinched 
  condition 
  of 
  the 
  rock. 
  

  

  In 
  one 
  of 
  the 
  railway 
  cuts 
  north 
  of 
  Whitehall 
  and 
  south 
  of 
  South 
  

   bay 
  specimen 
  67 
  was 
  gathered 
  and 
  was 
  regarded 
  as 
  a 
  quartzite 
  

   in 
  the 
  field. 
  Under 
  the 
  microscope 
  the 
  same 
  impression 
  is 
  diffi- 
  

   cult 
  to 
  avoid. 
  The 
  rock 
  is 
  a 
  finely 
  granular 
  aggregate 
  of 
  quartz 
  

   and 
  looks 
  very 
  like 
  a 
  sediment. 
  It 
  is 
  however 
  in 
  the 
  midst 
  of 
  

   eruptives 
  and 
  it 
  has 
  been 
  greatly 
  crushed 
  and 
  compressed. 
  

  

  If 
  both 
  these 
  rocks, 
  54 
  and 
  67, 
  are 
  not 
  considered 
  to 
  be 
  sedi- 
  

   ments 
  they 
  must 
  be 
  interpreted 
  as 
  pegmatites 
  of 
  such 
  extreme 
  

   richness 
  in 
  silica 
  as 
  to 
  have 
  been 
  practically 
  quartz 
  veins. 
  The 
  

   pegmatites 
  were 
  then 
  crushed 
  and 
  granulated. 
  It 
  is 
  possible 
  

   that 
  an 
  originally 
  less 
  siliceous 
  rock 
  has 
  been 
  enriched 
  in 
  silica 
  

   after 
  having 
  been 
  crushed, 
  but 
  if 
  this 
  is 
  true, 
  the 
  process 
  can 
  not 
  

   be 
  readily 
  if 
  at 
  all 
  traced 
  out, 
  and 
  demonstrated 
  with 
  the 
  material 
  

   in 
  hand. 
  The 
  graphite 
  strongly 
  suggests 
  a 
  sedimentary 
  origin, 
  

   but 
  it 
  is 
  not 
  proof 
  positive, 
  because 
  it 
  is 
  not 
  lacking 
  in 
  the 
  pegma- 
  

   tites 
  of 
  the 
  region. 
  The 
  old 
  graphite 
  mines 
  at 
  Chilson 
  hill 
  in 
  

   Ticonderoga 
  are 
  on 
  pegmatite 
  dikes 
  or 
  veins. 
  On 
  the 
  whole, 
  

   however, 
  the 
  writers 
  are 
  inclined 
  to 
  favor 
  the 
  sedimentary 
  origin, 
  

   and 
  we 
  hope 
  to 
  work 
  out 
  the 
  stratigraphy 
  more 
  in 
  detail 
  in 
  the 
  

   future. 
  Every 
  outcrop 
  should 
  be 
  mapped 
  and 
  the 
  relations 
  

  

  