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

  

  29 
  

  

  m, 
  the 
  other 
  about 
  5° 
  of 
  a 
  possible 
  pyramid 
  221 
  of 
  graftonite. 
  

   It 
  must 
  furthermore 
  be 
  borne 
  in 
  mind 
  that 
  the 
  variable 
  

   elements, 
  that 
  is, 
  the 
  axial 
  ratios, 
  of 
  both 
  triphylite 
  and 
  graf- 
  

   tonite 
  have 
  been 
  derived 
  from 
  measurements 
  made 
  with 
  only 
  a 
  

   contact 
  goniometer, 
  hence 
  the 
  correspondence 
  between 
  the 
  two 
  

   minerals 
  may 
  be 
  even 
  closer 
  than 
  is 
  indicated 
  by 
  their 
  position 
  

   as 
  plotted 
  on 
  the 
  spherical 
  projection. 
  

  

  Another 
  and 
  perhaps 
  a 
  more 
  convincing 
  method 
  of 
  showing 
  

   similarity 
  between 
  the 
  two 
  minerals 
  is 
  given 
  by 
  fig. 
  9. 
  This 
  

   represents 
  at 
  the 
  left 
  a 
  monoclinic 
  combination 
  of 
  the 
  forms 
  m 
  

   and 
  d 
  of 
  graftonite, 
  with 
  the 
  right 
  hand 
  edge 
  of 
  the 
  prism 
  

   truncated 
  by 
  a 
  clinopinacoid 
  b. 
  To 
  the 
  right 
  is 
  a 
  triphylite 
  

   crystal, 
  representing 
  a 
  combination 
  of 
  the 
  domes 
  W, 
  102, 
  and 
  

   D, 
  021, 
  accurately 
  plotted, 
  and 
  drawn 
  so 
  that 
  one 
  of 
  the 
  W 
  

   faces 
  is 
  in 
  contact 
  with 
  the 
  clinopinacoid 
  of 
  the 
  graftonite 
  and 
  

   the 
  edge 
  W^W 
  parallel 
  to 
  the 
  clino-axis 
  of 
  the 
  latter 
  mineral. 
  

   Thus 
  drawn, 
  a 
  d 
  face 
  of 
  the 
  one 
  crystal 
  and 
  a 
  W 
  face 
  of 
  the 
  

   other 
  full 
  almost 
  exactly 
  in 
  one 
  plane 
  (W^ 
  W 
  = 
  62° 
  23' 
  and 
  

   £a'/=62°), 
  and, 
  also 
  a 
  brachydome 
  face 
  D 
  of 
  the 
  triphylite 
  

  

  