﻿32 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  of 
  massive, 
  coarsely 
  crystalline 
  quartz, 
  running 
  up 
  to 
  as 
  high 
  as 
  

   c;o^ 
  of 
  the 
  rock, 
  though 
  feldspars 
  and 
  accessory 
  minerals 
  are 
  always 
  

   present. 
  The 
  thinner 
  quartzite 
  beds 
  are 
  generally 
  more 
  impure, 
  

   though 
  containing 
  layers 
  of 
  coarse, 
  massive, 
  quite 
  pure 
  quartzite. 
  

   The 
  impurer 
  beds 
  are 
  often 
  well 
  foliated, 
  consisting 
  of 
  alternate 
  

   films 
  of 
  pure 
  quartz 
  and 
  of 
  other 
  minerals, 
  the 
  former 
  very 
  resistant 
  

   to 
  the 
  weather, 
  the 
  latter 
  less 
  so, 
  so 
  that 
  on 
  the 
  weathered 
  surfaces 
  

   the 
  contortions 
  and 
  puckering;s 
  of 
  the 
  complexly 
  folded 
  schist 
  

   series 
  are 
  much 
  more 
  perfectly 
  displayed 
  than 
  in 
  any 
  other 
  rock 
  

   type 
  of 
  the 
  region. 
  They 
  are 
  often 
  very 
  close 
  jointed, 
  especially 
  

   near 
  granite, 
  weathering 
  out 
  into 
  small 
  blocks 
  [pi. 
  3]. 
  

  

  Much 
  of 
  the 
  quartzite 
  of 
  the 
  district 
  is 
  more 
  or 
  less 
  permeated 
  

   with 
  brown, 
  iron-stained 
  spots, 
  due 
  to 
  the 
  weathering 
  out 
  of 
  some 
  

   mineral 
  with 
  iron 
  in 
  its 
  composition. 
  These 
  spots 
  vary 
  greatly 
  in 
  

   abundance 
  in 
  different 
  occurrences 
  and 
  different 
  layers, 
  and 
  may 
  

   have 
  a 
  fairly 
  uniform 
  distribution, 
  or, 
  in 
  the 
  foliated 
  varieties, 
  be 
  

   confined 
  to 
  the 
  films 
  containing 
  other 
  minerals 
  than 
  quartz, 
  giving 
  

   a 
  brown 
  and 
  white, 
  banded 
  rock. 
  In 
  some 
  cases, 
  notably 
  those 
  of 
  

   the 
  first 
  type, 
  the 
  mineral 
  removed 
  seems 
  to 
  have 
  been 
  pyrite, 
  a 
  

   mineral 
  of 
  consistent 
  occurrence 
  in 
  the 
  quartzite 
  ; 
  in 
  other 
  cases 
  

   it 
  seems 
  to 
  have 
  been 
  pyroxene, 
  though 
  even 
  here 
  probably 
  oxidized 
  

   pyrite 
  was 
  responsible 
  for 
  most 
  of 
  the 
  yellow, 
  iron 
  stain. 
  

  

  In 
  texture 
  the 
  rock 
  shows 
  great 
  variation, 
  ranging 
  from 
  the 
  very 
  

   coarsely 
  crystalline, 
  glassy 
  rocks, 
  down 
  to 
  varieties 
  which 
  have 
  a 
  

   finely 
  granular 
  make-up. 
  

  

  Next 
  to 
  quartz, 
  feldspars 
  form 
  the 
  most 
  prominent 
  mineral 
  con- 
  

   stituent, 
  orthoclase, 
  microperthite 
  and 
  oligoclase 
  all 
  occurring. 
  

   Much 
  variation 
  in 
  relative 
  amounts 
  of 
  the 
  two 
  mineral 
  groups 
  is 
  

   shown, 
  but 
  in 
  the 
  great 
  bulk 
  of 
  the 
  rock, 
  cjuartz 
  is 
  in 
  excess 
  and 
  

   usually 
  greatly 
  in 
  excess. 
  In 
  some 
  varieties 
  white 
  to 
  light 
  green 
  

   pyroxene 
  appears 
  in 
  quantity, 
  when 
  the 
  feldspar 
  retreats. 
  There 
  is 
  

   considerable 
  of 
  such 
  quartz-pyroxene 
  gneiss 
  in 
  the 
  region, 
  the 
  

   quartz 
  usually 
  constituting 
  y^^^ 
  of 
  the 
  rock. 
  Light 
  brown 
  mica 
  

   (phlogopite) 
  is 
  sparingly 
  present 
  in 
  much 
  of 
  the 
  quartzite, 
  and 
  some 
  

   varieties 
  become 
  quite 
  micaceous. 
  Pyrite 
  is 
  a 
  frequent 
  mineral, 
  

   as 
  has 
  been 
  stated. 
  Zircon 
  and 
  titanite 
  are 
  nearly 
  always 
  present, 
  

   and 
  at 
  times 
  fine 
  needles 
  of 
  rutile 
  are 
  abundantly 
  included. 
  

  

  Here 
  and 
  there 
  in 
  the 
  region 
  rocks 
  are 
  found 
  which 
  present 
  a 
  

   puzzling 
  half 
  way 
  stage 
  between 
  quartzite 
  and 
  granite, 
  so 
  that 
  they 
  

   are 
  likely 
  to 
  be 
  classed, 
  now 
  with 
  one 
  rock, 
  and 
  again 
  with 
  the 
  

   other, 
  according 
  as 
  the 
  observer 
  comes 
  upon 
  them 
  from 
  quartzite, 
  

   or 
  from 
  granite. 
  In 
  all 
  cases 
  where 
  the 
  relations 
  could 
  be 
  worked 
  

  

  