﻿178 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  for 
  analytical 
  purposes 
  could 
  be 
  obtained 
  from 
  the 
  adjacent 
  red 
  

   granite 
  of 
  the 
  same 
  boss, 
  and 
  this 
  white 
  granite 
  stands 
  as 
  the 
  only 
  

   border 
  rock 
  of 
  any 
  of 
  the 
  granites 
  which 
  has 
  been 
  analyzed. 
  The 
  

   field 
  relations 
  of 
  all 
  the 
  granite 
  masses 
  indicate 
  that 
  their 
  border 
  

   zones, 
  and 
  the 
  dikes 
  which 
  run 
  out 
  from 
  them, 
  are 
  more 
  acid 
  than 
  

   the 
  general 
  mass 
  of 
  the 
  rock, 
  higher 
  in 
  quartz 
  and 
  with 
  much 
  less 
  

   biotite 
  and 
  magnetite. 
  Now 
  the 
  granite 
  cuts 
  and 
  sends 
  dikes 
  into 
  

   all 
  the 
  Grenville 
  rocks, 
  all 
  of 
  this 
  more 
  acid 
  phas-e, 
  yet 
  it 
  is 
  only 
  

   in 
  the 
  case 
  of 
  adjacent 
  limestone 
  that 
  the 
  border 
  and 
  the 
  dikes 
  

   become 
  white. 
  In 
  the 
  schists 
  and 
  quartzites 
  they 
  remain 
  red, 
  though 
  

   equally 
  acid 
  with 
  the 
  white. 
  In 
  so 
  far 
  then 
  as 
  the 
  higher 
  silica 
  

   and 
  lower 
  iron 
  of 
  the 
  white 
  granite 
  are 
  concerned, 
  the 
  rock 
  is 
  be- 
  

   lieved 
  to 
  be 
  merely 
  an 
  average 
  representative 
  of 
  the 
  general, 
  more 
  

   acid 
  border 
  rock, 
  it 
  being 
  confidently 
  held 
  that 
  much 
  of 
  the 
  red, 
  

   border 
  granite 
  or 
  dike 
  granite 
  Vv^ould 
  show 
  equivalent 
  acidity, 
  and 
  

   like 
  diminution 
  in 
  iron, 
  and 
  that 
  the 
  color 
  change 
  is 
  in 
  no 
  way 
  con- 
  

   cerned 
  in 
  these 
  differences. 
  Though 
  no 
  chemical 
  analyses 
  are 
  avail- 
  

   able, 
  study 
  of 
  slides 
  of 
  these 
  acid 
  red 
  granites 
  gives 
  results 
  in 
  close 
  

   accord 
  with 
  the 
  analysis 
  of 
  the 
  white, 
  and 
  many 
  of 
  them 
  show 
  

   almost 
  no 
  biotite 
  and 
  magnetite 
  in 
  the 
  rock, 
  hence 
  they 
  are 
  much 
  

   poorer 
  in 
  iron 
  than 
  the 
  rock 
  of 
  analysis 
  4, 
  though 
  with 
  feldspar 
  

   equally 
  as 
  red 
  in 
  color. 
  Slight 
  differentiation 
  has 
  taken 
  place 
  in 
  

   the 
  granite, 
  producing 
  more 
  acid 
  borders 
  and 
  dikes, 
  and 
  these 
  

   bleached 
  only 
  by 
  limestone. 
  

  

  The 
  rock 
  classes 
  as 
  a 
  toscanose, 
  as 
  do 
  the 
  others. 
  Yet 
  it 
  is 
  close 
  

   to 
  the 
  border 
  line 
  between 
  orders 
  3 
  and 
  4, 
  as 
  shown 
  by 
  its 
  -close 
  

   similarity 
  in 
  composition 
  with 
  the 
  red, 
  ^lorris 
  granite 
  of 
  analysis 
  2, 
  

   which 
  falls 
  in 
  order 
  3 
  and 
  is 
  an 
  alaskose. 
  

  

  There 
  is 
  every 
  reason 
  to 
  believe 
  that 
  the 
  coloring 
  matter 
  of 
  the 
  

   red 
  feldspar 
  is 
  ferric 
  oxid 
  ; 
  in 
  fact 
  in 
  some 
  of 
  the 
  thin 
  sections, 
  

   minute, 
  red 
  hematite 
  scales 
  are 
  readily 
  made 
  out 
  with 
  high 
  powers. 
  

   In 
  casting 
  about 
  for 
  some 
  chemical 
  explanation 
  of 
  the 
  bleaching 
  of 
  

   the 
  feldspar, 
  chance 
  put 
  me 
  in 
  communication 
  with 
  Dr 
  W. 
  F. 
  Hil- 
  

   lebrand, 
  who 
  most 
  generously 
  furnished 
  me 
  such 
  data 
  as 
  he 
  had 
  at 
  

   command. 
  He 
  writes 
  as 
  follows 
  : 
  

  

  Many 
  years 
  ago, 
  in 
  Denver, 
  I 
  had 
  occasion 
  to 
  analyze 
  a 
  zeolite 
  

   that 
  was 
  colored 
  red 
  by 
  iron 
  oxid. 
  On 
  ignition 
  the 
  red 
  color 
  

   disappeared 
  entirely 
  and 
  almost 
  pure 
  white 
  resulted. 
  This 
  was 
  

   undoubtedly 
  due 
  to 
  a 
  combination 
  between 
  the 
  iron 
  oxid 
  and 
  the 
  

   silicate 
  material. 
  My 
  impression 
  is 
  that 
  the 
  zeolite 
  was 
  a 
  cal- 
  

   cium-aluminum 
  silicate. 
  Since 
  then 
  I 
  have 
  seen 
  in 
  the 
  Chemical 
  

   N'ezi's, 
  vol. 
  84, 
  p. 
  305. 
  a 
  reference 
  to 
  the 
  decolorizing 
  effect 
  of 
  

   alumina 
  on 
  ferric 
  oxid 
  when 
  the 
  two 
  are 
  ignited 
  together 
  . 
  . 
  . 
  

  

  