﻿Pratt 
  and 
  Foote- 
  

  

  Wellsite, 
  a 
  new 
  Mineral. 
  

  

  445 
  

  

  due 
  to 
  the 
  difference 
  in 
  the 
  ratio 
  of 
  the 
  barium 
  to 
  the 
  calcium 
  

   in 
  the 
  different 
  crystals. 
  

  

  A 
  section 
  parallel 
  to 
  the 
  pinacoid 
  faces 
  h, 
  010, 
  the 
  apparent 
  

   prism, 
  revealed 
  in 
  polarized 
  light 
  the 
  structure 
  shown 
  in 
  fig. 
  3. 
  

   The 
  parts 
  I 
  and 
  I 
  extinguish 
  simultaneously, 
  as 
  also 
  II 
  and 
  II 
  ; 
  

   while 
  portions 
  III, 
  which 
  are 
  parallel 
  to 
  the 
  basal 
  plane, 
  show 
  

   parallel 
  extinction. 
  The 
  section 
  showed 
  something 
  of 
  a 
  zonal 
  

   structure, 
  so 
  that 
  the 
  extinction 
  could 
  only 
  be 
  measured 
  approxi- 
  

   mately. 
  Using 
  the 
  Bertrand 
  ocular, 
  this 
  was 
  found 
  to 
  be 
  33° 
  

   from 
  one 
  pinacoid 
  on 
  to 
  the 
  other 
  over 
  the 
  twinning 
  plane. 
  

   The 
  axis 
  a 
  makes 
  an 
  angle 
  of 
  52° 
  with 
  the 
  vertical 
  axis 
  6 
  in 
  the 
  

   obtuse 
  angle 
  /?. 
  

  

  The 
  double 
  refraction 
  is 
  posi- 
  

   tive 
  and 
  weak. 
  The 
  acute 
  

   bisectrix 
  c 
  is 
  at 
  right 
  angles 
  to 
  

   the 
  pinacoid 
  010, 
  and 
  the 
  diver- 
  

   gence 
  of 
  the 
  optical 
  axes 
  is 
  

   large. 
  2E 
  probably 
  varies 
  from 
  

   120° 
  to 
  130°, 
  but 
  this 
  could 
  not 
  

   be 
  measured 
  directly. 
  

  

  Chemical 
  analysis. 
  — 
  The 
  

   mineral 
  was 
  purified 
  for 
  analy- 
  

   sis 
  by 
  means 
  of 
  the 
  heavy 
  solu- 
  

   tion 
  and 
  that 
  which 
  was 
  used 
  

   varied 
  in 
  specific 
  gravity 
  from 
  

   2*278 
  to 
  2-360. 
  Water 
  was 
  

   determined 
  by 
  loss 
  on 
  ignition 
  

   and 
  silica 
  and 
  alumina 
  by 
  the 
  

   ordinary 
  methods 
  after 
  fusion 
  

   with 
  sodium 
  carbonate. 
  The 
  

   filtrate 
  from 
  the 
  alumina 
  pre- 
  

   cipitation 
  was 
  evaporated 
  with 
  

   aqua 
  regia 
  to 
  remove 
  the 
  large 
  

   excess 
  of 
  ammonium 
  salts 
  and 
  

   a 
  small 
  amount 
  of 
  ammonium 
  chloride 
  was 
  again 
  added. 
  Cal- 
  

   cium, 
  barium 
  and 
  strontium 
  were 
  then 
  precipitated 
  together, 
  

   with 
  a 
  considerable 
  excess 
  of 
  ammonia 
  and 
  ammonium 
  carbo- 
  

   nate, 
  and 
  magnesia 
  was 
  determined 
  in 
  the 
  filtrate. 
  The 
  mixed 
  

   carbonates 
  were 
  dissolved 
  in 
  hydrochloric 
  acid, 
  evaporated 
  to 
  

   dryness 
  and 
  taken 
  up 
  in 
  about 
  300 
  cc 
  of 
  water. 
  The 
  method 
  

   used 
  for 
  separating 
  barium 
  was 
  that 
  recommended 
  by 
  Fre- 
  

   senius.* 
  To 
  the 
  hot 
  solution, 
  a 
  few 
  drops 
  of 
  acetic 
  acid 
  were 
  

   added 
  and 
  10 
  cc 
  of 
  a 
  10 
  per 
  cent 
  solution 
  of 
  ammonium 
  chro- 
  

   mate 
  containing 
  a 
  small 
  amount 
  of 
  dichromate. 
  After 
  stand- 
  

   ing 
  until 
  the 
  solution 
  became 
  cold, 
  the 
  clear 
  liquid 
  was 
  decanted 
  

  

  *Zs. 
  Anal. 
  Chem., 
  xxix, 
  426. 
  

  

  Am. 
  Jour. 
  Sci.— 
  Fourth 
  Series, 
  Yol. 
  Ill, 
  No. 
  18.— 
  June, 
  1897. 
  

   31 
  

  

  