﻿Luedeking 
  and 
  Wheeler 
  — 
  Notes 
  on 
  a 
  Missouri 
  Barite. 
  497 
  

  

  and 
  persistently 
  occurs 
  in 
  all 
  the 
  Smithton 
  specimens 
  that 
  

   have 
  been 
  examined 
  in 
  relatively 
  the 
  same 
  position 
  with 
  re- 
  

   spect 
  to 
  the 
  development 
  of 
  the 
  crystal, 
  whether 
  large 
  or 
  small 
  

   in 
  size. 
  The 
  white 
  coating 
  that 
  fringes 
  the 
  crystals 
  is 
  usually 
  

   superficial, 
  as 
  it 
  most 
  frequently 
  is 
  found 
  to 
  be 
  underlaid 
  by 
  a 
  

   clear 
  wine-colored 
  ground 
  mass 
  ; 
  in 
  some 
  crystals 
  however 
  the 
  

   opaque 
  matter 
  entirely 
  replaces 
  this 
  latter. 
  

  

  The 
  simple 
  tabular 
  crystal 
  C 
  has 
  a 
  clear 
  colorless 
  interior 
  

   inclosed 
  within 
  a 
  subtransparent 
  wine-colored 
  band 
  l-5 
  mm 
  in 
  

   width, 
  that 
  is 
  adjoined 
  by 
  a 
  white 
  opaque 
  band 
  0'5 
  mm 
  in 
  width 
  ; 
  

   both 
  of 
  these 
  bands 
  are 
  parallel 
  to 
  the 
  prismatic 
  faces 
  as 
  like- 
  

   wise 
  the 
  cleavage 
  crack 
  shown 
  in 
  the 
  drawing. 
  The 
  outer 
  

   edge 
  of 
  this 
  crystal 
  is 
  transparent 
  but 
  has 
  the 
  slight 
  bluish 
  

   tinge 
  indicative 
  of 
  strontium. 
  

  

  The 
  twinned 
  group 
  of 
  crystals 
  shown 
  in 
  D 
  have 
  the 
  edges 
  

   of 
  the 
  right 
  rhombic 
  prism 
  modified 
  by 
  either 
  one, 
  two 
  or 
  

   three 
  modifications 
  of 
  the 
  macrodome, 
  and 
  truncated 
  as 
  usual 
  

   by 
  the 
  basal 
  pinacoid 
  ; 
  in 
  this 
  type 
  only 
  the 
  faces 
  of 
  the 
  prism 
  

   are 
  coated 
  with 
  the 
  opaque 
  white 
  barite, 
  the 
  rest 
  of 
  the 
  mate- 
  

   rial 
  consisting 
  of 
  clear 
  colorless 
  and 
  essentially 
  pure 
  barite. 
  

   The 
  thickness 
  of 
  this 
  coating 
  is 
  variable 
  on 
  different 
  faces 
  of 
  

   the 
  prism, 
  being 
  appreciably 
  greater 
  on 
  the 
  upper 
  face 
  in 
  some 
  

   and 
  on 
  the 
  lower 
  face 
  in 
  other 
  crystals 
  and 
  varying 
  from 
  0*2 
  

   to 
  2'2 
  mm 
  in 
  thickness 
  ; 
  but 
  in 
  every 
  case 
  the 
  opaque 
  barite 
  is 
  

   only 
  found 
  on 
  the 
  prismatic 
  faces. 
  

  

  The 
  crystal 
  E 
  is 
  a 
  member 
  of 
  the 
  same 
  cluster 
  of 
  crystals 
  

   from 
  which 
  D 
  was 
  taken. 
  It 
  consists 
  of 
  only 
  the 
  simple 
  

   rhombic 
  prism 
  which 
  is 
  thinly 
  fringed 
  with 
  white 
  barite, 
  but 
  

   on 
  one 
  of 
  the 
  basal 
  faces 
  is 
  a 
  series 
  of 
  irregular 
  lines 
  of 
  a 
  fine 
  

   white 
  pulverulent 
  material 
  that 
  suggests 
  the 
  deposition 
  of 
  a 
  

   sediment 
  on 
  an 
  inclined 
  surface. 
  A 
  subsequent 
  deposition 
  of 
  

   clear 
  barite 
  has 
  preserved 
  this 
  pulverulent 
  matter 
  in 
  situ. 
  

  

  An 
  analysis 
  of 
  the 
  white 
  barite 
  showed 
  it 
  to 
  be 
  somewhat 
  

   variable 
  in 
  composition, 
  but 
  the 
  following 
  gives 
  its 
  general 
  

   character. 
  

  

  Barium 
  sulphate 
  __ 
  87*2 
  per 
  cent. 
  

  

  Strontium 
  sulphate 
  10*9 
  " 
  

  

  Calcium 
  sulphate 
  0-2 
  " 
  

  

  Ammonium 
  sulphate 
  0-2 
  " 
  

  

  Water 
  2*4 
  " 
  

  

  100-9 
  

  

  The 
  occurrence 
  of 
  ammonium 
  sulphate 
  in 
  barite 
  is 
  quite 
  

   novel. 
  The 
  amount 
  seems 
  to 
  be 
  somewhat 
  greater 
  in 
  the 
  yel- 
  

   low 
  than 
  in 
  the 
  white 
  variety 
  by 
  about 
  0*1 
  per 
  cent 
  and 
  is 
  

  

  