﻿28 
  S. 
  L. 
  Penfield 
  — 
  Graftonite,a 
  new 
  Mineral. 
  

  

  lamination, 
  and 
  differently 
  in 
  different 
  lamellae, 
  as 
  indicated 
  by 
  

   the 
  arrows, 
  fig. 
  1. 
  In 
  lamellae 
  1, 
  3 
  and 
  the 
  upper 
  part 
  of 
  5 
  

   the 
  extinction 
  is 
  to 
  the 
  right, 
  while 
  in 
  2, 
  6, 
  7 
  and 
  the 
  lower 
  

   part 
  of 
  5 
  it 
  is 
  to 
  the 
  left. 
  Thus 
  evidently 
  the 
  orthorhombic 
  

   triphylite 
  and 
  the 
  monoclinic 
  graftonite 
  have 
  not 
  intergrown 
  

   with 
  pinacoid 
  faces 
  in 
  common, 
  for 
  in 
  that 
  case 
  both 
  minerals 
  

   would 
  have 
  shown 
  parallel 
  extinction. 
  The 
  inclined 
  extinction 
  

   of 
  the 
  triphylite 
  naturally 
  suggested 
  the 
  idea 
  that 
  one 
  of 
  its 
  

   prism 
  or 
  dome 
  faces 
  might 
  be 
  parallel 
  to 
  the 
  clinopinacoid 
  of 
  

   the 
  graftonite, 
  and, 
  on 
  looking 
  for 
  some 
  similarity 
  between 
  the 
  

   forms 
  and 
  angles 
  of 
  the 
  two 
  minerals, 
  it 
  was 
  observed 
  that 
  the 
  

   angle 
  of 
  the 
  macrodome 
  102 
  of 
  triphylite 
  (102 
  /\ 
  102 
  = 
  

   62° 
  23') 
  was 
  practically 
  the 
  same 
  as 
  the 
  angle 
  between 
  the 
  

   clinodome 
  d, 
  Oil, 
  and 
  the 
  clino-pinacoid 
  &, 
  010, 
  of 
  graftonite 
  

   (011 
  /\ 
  010 
  = 
  62°). 
  If 
  therefore 
  a 
  triphylite 
  crystal 
  is 
  orien- 
  

   tated 
  so 
  that 
  its 
  macro-axis 
  is 
  parallel 
  to 
  the 
  clino 
  axis 
  of 
  graf- 
  

   tonite, 
  and 
  is 
  then 
  tipped 
  31° 
  so 
  that 
  a 
  dome 
  face 
  102 
  comes 
  

   in 
  contact 
  with 
  the 
  clinopinacoid 
  b 
  of 
  graftonite, 
  then 
  the 
  

   clinodome 
  d 
  of 
  the 
  graftonite 
  and 
  the 
  macrodome 
  of 
  the 
  tri- 
  

   phylite 
  fall 
  practically 
  in 
  one 
  plane. 
  In 
  trying 
  to 
  find 
  other 
  

   points 
  of 
  similarity 
  which 
  the 
  two 
  minerals 
  might 
  possess, 
  

   recourse 
  w 
  r 
  as 
  had 
  to 
  the 
  spherical 
  projection. 
  Fig. 
  8 
  represents 
  

   in 
  its 
  full 
  lines 
  the 
  spherical 
  projection 
  of 
  graftonite, 
  the 
  loca- 
  

   tion 
  of 
  the 
  forms 
  recorded 
  on 
  p. 
  24 
  being 
  indicated 
  by 
  italic 
  

   letters, 
  while 
  the 
  location 
  of 
  four 
  forms, 
  001, 
  031, 
  301 
  and 
  221, 
  

   which 
  were 
  not 
  observed 
  as 
  crystal 
  faces, 
  are 
  indicated 
  by 
  

   indices 
  in 
  small 
  figures. 
  The 
  projection 
  of 
  the 
  triphylite 
  is 
  

   given 
  in 
  dotted 
  lines, 
  the 
  known 
  forms 
  being 
  indicated 
  by 
  

   heavy, 
  full-faced 
  letters, 
  while 
  the 
  indices 
  of 
  a 
  few 
  possible 
  

   forms 
  are 
  also 
  given 
  in 
  heavy 
  figures. 
  The 
  lettered 
  forms 
  of 
  

   the 
  triphylite 
  are 
  as 
  follows 
  : 
  

  

  

  B, 
  010 
  

  

  M, 
  

  

  110 
  

  

  W, 
  102 
  

  

  V, 
  302 
  

  

  C, 
  ooi 
  

  

  U 
  

  

  120 
  

  

  E, 
  101 
  

  

  D, 
  021 
  

  

  As" 
  a 
  starting 
  point 
  in 
  constructing 
  the 
  projection 
  of 
  the 
  

   triphylite, 
  the 
  zone 
  in 
  which 
  100 
  and 
  C, 
  001, 
  are 
  located 
  

   was 
  made 
  to 
  coincide 
  with 
  the 
  zone 
  b, 
  d, 
  d 
  7 
  of 
  the 
  graftonite, 
  

   and 
  the 
  location 
  of 
  two 
  faces 
  of 
  the 
  macrodome 
  W 
  of 
  the 
  

   triphylite 
  to 
  coincide, 
  one 
  with 
  the 
  clinodome 
  d, 
  the 
  other 
  

   with 
  the 
  clinopinacoid 
  b 
  of 
  the 
  graftonite. 
  Thus, 
  as 
  shown 
  

   by 
  the 
  figure, 
  the 
  forms 
  C, 
  V 
  and 
  100 
  of 
  triphylite 
  corre- 
  

   spond 
  closely 
  to 
  031, 
  001 
  and 
  d, 
  011 
  of 
  graftonite 
  respectively. 
  

   A 
  zone 
  W, 
  122, 
  M, 
  W 
  of 
  triphylite 
  is 
  almost 
  coincident 
  with 
  

   that 
  joining 
  b 
  and 
  p 
  of 
  graftonite, 
  though 
  the 
  forms 
  M 
  and 
  

   1 
  22 
  of 
  the 
  former 
  are 
  located 
  several 
  degrees 
  distant 
  from 
  

   the 
  pyramid 
  p 
  of 
  the 
  latter. 
  Finally 
  the 
  faces 
  of 
  the 
  dome 
  D, 
  

   021 
  and 
  021, 
  of 
  triphylite 
  fall 
  one 
  within 
  about 
  3° 
  of 
  the 
  prism 
  

  

  