﻿14 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Feldspar-quartz 
  light 
  gneisses 
  also 
  occur 
  three-quarters 
  of 
  a 
  mile 
  

   south 
  of 
  Thurman 
  ; 
  at 
  Starbuckville 
  ; 
  and 
  one-quarter 
  of 
  a 
  mile 
  

   north 
  of 
  Chestertown. 
  

  

  Pyroxene 
  gneisses. 
  These 
  gneisses 
  are 
  much 
  less 
  abundant 
  than 
  

   those 
  above 
  described. 
  The 
  most 
  common 
  facies 
  is 
  a 
  fine 
  to 
  me- 
  

   dium-grained 
  intimate 
  mixture 
  of 
  small 
  grains 
  or 
  crystals 
  of 
  green 
  

   pyroxene 
  and 
  reddish 
  brown 
  garnet, 
  with 
  sometimes 
  one 
  and 
  some- 
  

   times 
  the 
  other 
  predominating. 
  Such 
  rocks 
  are 
  well 
  exposed 
  in 
  the 
  

   Sanders 
  Brothers 
  mine 
  near 
  the 
  mouth 
  of 
  Mill 
  creek, 
  and 
  at 
  the 
  

   old 
  Parker 
  mine 
  just 
  southwest 
  of 
  Daggett 
  pond. 
  

  

  Another 
  facies 
  is 
  a 
  greenish 
  gray 
  to 
  greenish 
  gneiss 
  which 
  con- 
  

   tains 
  more 
  or 
  less 
  feldspar 
  in 
  addition 
  to 
  the 
  small 
  garnets. 
  Such 
  

   rock 
  makes 
  up 
  the 
  inclusion 
  I 
  .mile 
  west 
  of 
  The 
  Glen, 
  and 
  also 
  

   occurs 
  along 
  the 
  road 
  one-quarter 
  of 
  a 
  mile 
  north 
  of 
  the 
  north 
  

   end 
  of 
  Loon 
  lake. 
  Interbedded 
  with 
  the 
  rock 
  at 
  this 
  last 
  named 
  

   locality 
  is 
  a 
  schistose 
  orthoclase, 
  green 
  pyroxene, 
  phlogopite 
  rock, 
  

   with 
  occasional 
  graphite 
  flakes 
  up 
  to 
  3 
  or 
  4 
  millimeters 
  across. 
  

  

  Sillimanite-feldspar-garnet 
  gneisses. 
  Such 
  rocks 
  were 
  observed 
  

   at 
  but 
  two 
  localities, 
  namely, 
  three-quarters 
  of 
  a 
  mile 
  west-north- 
  

   west 
  of 
  Starbuckville 
  and 
  1 
  mile 
  south 
  of 
  South 
  Horicon. 
  A 
  thin 
  

   section 
  and 
  specimen 
  from 
  the 
  large 
  outcrop 
  at 
  the 
  latter 
  place 
  

   shows 
  the 
  rock 
  to 
  be 
  fairly 
  coarse-grained, 
  gray, 
  moderately 
  

   gneissoid 
  and 
  made 
  up 
  of 
  a 
  matrix 
  of 
  orthoclase, 
  microperthite, 
  

   and 
  quartz 
  in 
  which 
  are 
  embedded 
  many 
  pale 
  pink 
  garnets, 
  small 
  

   prisms 
  of 
  sillimanite, 
  tiny 
  graphite 
  flakes, 
  and 
  some 
  small 
  magnetite 
  

   and 
  colorless 
  pyroxene 
  crystals. 
  At 
  the 
  first 
  named 
  locality 
  the 
  

   rock 
  is 
  well 
  banded 
  and 
  contains 
  fibrous 
  sillimanite 
  in 
  irregular 
  

   streaks 
  and 
  also 
  some 
  biotite. 
  

  

  Graphite 
  sehists 
  or 
  gneisses. 
  As 
  we 
  have 
  learned, 
  graphite 
  flakes 
  

   are 
  common 
  in 
  the 
  limestone 
  and 
  sometimes 
  present 
  in 
  the 
  quartz- 
  

   ites 
  and 
  various 
  gneisses. 
  True 
  graphite 
  schists 
  or 
  gneisses 
  are, 
  

   however, 
  rare, 
  the 
  only 
  ones 
  noted 
  being 
  at 
  the 
  old 
  graphite 
  mine 
  

   1 
  mile 
  southwest 
  of 
  Johnsburg 
  where 
  the 
  rocks 
  are 
  light 
  to 
  dark 
  

   gray 
  and 
  thin 
  to 
  thick 
  bedded. 
  One 
  specimen 
  is 
  almost 
  a 
  quartzite, 
  

   but 
  with 
  numerous 
  small 
  biotite 
  and 
  graphite 
  flakes. 
  Another 
  

   specimen 
  is 
  a 
  feldspar-quartz 
  schistose 
  rock 
  without 
  biotite 
  and 
  

   fairly 
  filled 
  with 
  graphite 
  flakes 
  generally 
  from 
  1 
  to 
  2 
  millimeters 
  

   across. 
  Still 
  another 
  specimen 
  is 
  a 
  feldspar-quartz-biotite 
  gneiss 
  

   with 
  few 
  graphite 
  flakes. 
  

  

  Grenville 
  stratigraphy. 
  Any 
  attempt 
  to 
  work 
  out 
  the 
  strati- 
  

   graphy 
  of 
  the 
  Grenville 
  series 
  must 
  of 
  necessity 
  be 
  much 
  more 
  

  

  