﻿32 
  S. 
  L. 
  Penfield 
  — 
  Graftonite, 
  a 
  new 
  Mineral. 
  

  

  irregular 
  line 
  which 
  can 
  be 
  distinctly 
  traced 
  under 
  the 
  micro- 
  

   scope. 
  

  

  The 
  composite 
  crystals 
  of 
  graftonite 
  and 
  interlaminated 
  tri- 
  

   phylite 
  are 
  large, 
  and, 
  therefore, 
  it 
  seems 
  probable 
  that 
  a 
  very 
  

   longtime 
  would 
  be 
  required 
  for 
  their 
  growth 
  and 
  development. 
  

   It 
  does 
  not 
  seem 
  probable 
  that 
  the 
  crystals 
  could 
  have 
  been 
  

   originally 
  of 
  one 
  material 
  and 
  subsequently, 
  without 
  oxidation 
  

   of 
  the 
  iron 
  or 
  manganese, 
  have 
  been 
  changed 
  in 
  part 
  to 
  a 
  

   material 
  of 
  different 
  composition. 
  The 
  acceptance 
  of 
  such 
  a 
  

   theory 
  would 
  require 
  that 
  the 
  product 
  resulting 
  from 
  the 
  

   alteration 
  (in 
  this 
  case 
  the 
  rare 
  mineral 
  triphylite) 
  should 
  have 
  

   developed 
  as 
  interspersed 
  lamellae 
  having 
  definite 
  crystallo- 
  

   graphic 
  orientation 
  with 
  reference 
  to 
  the 
  original 
  material. 
  

   Again 
  it 
  does 
  not 
  seem 
  probable 
  that 
  they 
  were 
  at 
  one 
  time 
  

   wholly 
  graftonite, 
  and 
  that 
  later, 
  by 
  pressure 
  or 
  other 
  agency, 
  

   they 
  were 
  broken 
  up 
  into 
  lamellae, 
  leaving 
  interstices 
  for 
  the 
  

   subsequent 
  infiltration 
  of 
  triphylite 
  as 
  a 
  cementing 
  material. 
  

   The 
  crystals, 
  with 
  the 
  exception 
  perhaps 
  of 
  the 
  one 
  represented 
  

   by 
  fig. 
  8, 
  show 
  no 
  evidence 
  of 
  having 
  been 
  crushed 
  and 
  

   cemented 
  together, 
  nor 
  are 
  there 
  any 
  inequalities, 
  striations 
  or 
  

   offsets 
  visible 
  on 
  their 
  faces 
  to 
  lead 
  one 
  to 
  suspect 
  that 
  the 
  crys- 
  

   tals 
  have 
  been 
  opened 
  out 
  and 
  broadened 
  as 
  a 
  result 
  of 
  the 
  

   interlaminated 
  triphylite. 
  It 
  seems 
  rather 
  probable 
  that 
  the 
  

   crystals 
  must 
  have 
  developed 
  in 
  a 
  solution 
  or 
  medium 
  which 
  

   contained 
  the 
  chemical 
  constituents 
  for 
  the 
  formation 
  of 
  both 
  

   compounds, 
  and 
  that 
  the 
  growth 
  was 
  of 
  such 
  a 
  nature 
  that 
  

   graftonite 
  was 
  deposited 
  at 
  one 
  period 
  and 
  triphylite 
  at 
  another. 
  

   Thus, 
  according 
  as 
  the 
  supply 
  of 
  material 
  favorable 
  for 
  the 
  

   formation 
  of 
  the 
  one 
  compound 
  or 
  the 
  other 
  was 
  most 
  abund- 
  

   antly 
  at 
  hand, 
  the 
  growth 
  of 
  the 
  crystals 
  proceeded 
  until 
  the 
  

   large 
  interlaminated 
  individuals 
  were 
  formed. 
  

  

  It 
  is 
  to 
  be 
  regretted 
  that 
  only 
  one 
  small 
  fragment 
  of 
  fresh 
  

   unaltered 
  material, 
  without 
  definite 
  crystal 
  faces, 
  was 
  found. 
  

   The 
  material 
  as 
  a 
  whole 
  was 
  of 
  such 
  a 
  nature 
  that 
  accurate 
  

   crystallographic 
  measurements 
  could 
  not 
  be 
  made, 
  and 
  orien- 
  

   tated 
  sections 
  containing 
  unaltered 
  triphylite 
  could 
  not 
  be 
  pre- 
  

   pared, 
  hence 
  the 
  crystallographic 
  relations 
  of 
  the 
  two 
  minerals 
  

   have 
  not 
  been 
  established 
  with 
  absolute 
  certainty. 
  It 
  is 
  hoped, 
  

   however, 
  that 
  the 
  time 
  devoted 
  to 
  finding 
  even 
  a 
  possible 
  

   explanation 
  of 
  the 
  remarkable 
  intergrowth 
  presented 
  by 
  the 
  

   two 
  minerals 
  has 
  not 
  been 
  spent 
  in 
  vain. 
  

  

  Laboratory 
  of 
  Mineralogy 
  and 
  Petrography, 
  

  

  Sheffield 
  Scientific 
  School 
  of 
  Yale 
  University, 
  November, 
  1899. 
  

  

  