﻿118 
  F. 
  W. 
  Clarke 
  — 
  Constitution 
  of 
  Tourmaline. 
  

  

  clear. 
  The 
  green 
  tourmalines 
  are 
  all 
  lower 
  in 
  alumina, 
  and 
  

   range 
  downward 
  towards 
  the 
  iron 
  end 
  of 
  the 
  series; 
  and 
  like 
  

   the 
  latter 
  are 
  representable 
  as 
  mixtures 
  of 
  the 
  foUowiug 
  molec- 
  

   ular 
  types 
  : 
  

  

  A. 
  Al,(SiOJ,(BOJ, 
  . 
  B03(A10H) 
  . 
  Fe,H,. 
  

  

  B. 
  Al,(SiOJ,(BOJ,.B03Ca.Fe,H,. 
  

  

  C. 
  Al,(SiO 
  J,(BOJ, 
  . 
  B03LiH 
  . 
  AIJJ.H,. 
  

  

  D. 
  Al,(SiOJ,{BO 
  J, 
  . 
  B03NaH 
  . 
  Al3NaH,. 
  

  

  E. 
  Al,(SiOJ,(BOJ, 
  . 
  BO3H, 
  . 
  Al3NaH,. 
  

  

  Thus 
  the 
  dark, 
  opaque 
  green 
  tourmaline 
  from 
  Kumford, 
  Me., 
  

   is 
  a 
  molecular 
  mixture 
  corresponding 
  to 
  AgB^C^Dj^Eg 
  ; 
  the 
  

   similar 
  mineral 
  from 
  Auburn 
  is 
  AgB^CgDj^ 
  ; 
  the 
  light 
  green 
  

   from 
  Auburn, 
  A^BgC.oDgE,^ 
  ; 
  and 
  the 
  nearly 
  colorless 
  from 
  

   Auburn, 
  K^fj^^^^^^. 
  From 
  Brazil, 
  the 
  dark 
  green 
  is 
  

   AjB^CgDg, 
  and 
  the 
  liglit 
  green 
  is 
  A^B^CgDgE^. 
  The 
  complexity 
  

   of 
  these 
  expressions 
  is 
  only 
  apparent, 
  not 
  real 
  ; 
  as 
  a 
  study 
  of 
  

   the 
  original 
  type 
  formulae 
  will 
  show. 
  They 
  compare 
  with 
  the 
  

   reduced 
  analyses 
  as 
  follows 
  : 
  

  

  

  Rum 
  

   Found. 
  

  

  ford. 
  

  

  Auburn, 
  dark. 
  Auburn, 
  

  

  medium. 
  

  

  Auburn, 
  pale. 
  

  

  

  Calc. 
  

  

  Found. 
  

  

  Calc. 
  

  

  Found. 
  

  

  Calc. 
  

  

  Found. 
  

  

  Calc. 
  

  

  SiO„ 
  

  

  .. 
  36-68 
  

  

  36-69 
  

  

  36-37 
  

  

  36-45 
  

  

  37^95 
  

  

  37-52 
  

  

  38-25 
  

  

  37-92 
  

  

  BA- 
  

  

  - 
  10-26 
  

  

  10-69 
  

  

  9-98 
  

  

  10-63 
  

  

  10-57 
  

  

  10-94 
  

  

  10-30 
  

  

  11-05 
  

  

  AlO, 
  

  

  . 
  38-26 
  

  

  37-74 
  

  

  36-89 
  

  

  37-21 
  

  

  38-11 
  

  

  39-02 
  

  

  39-92 
  

  

  40-17 
  

  

  FeO 
  . 
  

  

  . 
  6-78 
  

  

  6-90 
  

  

  7-94 
  

  

  7-72 
  

  

  4-47 
  

  

  4-28 
  

  

  2-75 
  

  

  2-56 
  

  

  CaO 
  

  

  •34 
  

  

  -34 
  

  

  •17 
  

  

  •16 
  

  

  •50 
  

  

  -50 
  

  

  -43 
  

  

  •49 
  

  

  Na„0 
  

  

  . 
  3-12 
  

  

  3-07 
  

  

  3-19 
  

  

  3-14 
  

  

  2-58 
  

  

  2-58 
  

  

  2-55 
  

  

  2^53 
  

  

  Li„0. 
  

  

  •95 
  

  

  -94 
  

  

  1-06 
  

  

  1-07 
  

  

  1-35 
  

  

  1-35 
  

  

  1-34 
  

  

  r34 
  

  

  H,0. 
  

  

  .. 
  3-61 
  

   100-00 
  

  

  3-63 
  

   100-00 
  

  

  4-40 
  

   100-00 
  

  

  3-62 
  

  

  4-47 
  

  

  3-81 
  

  

  4-46 
  

   100-00 
  

  

  3-94 
  

  

  

  100-00 
  100-00 
  

  

  100-00 
  

  

  100-00 
  

  

  

  

  

  Brazil, 
  

  

  dark. 
  

  

  

  Brazil, 
  light. 
  

  

  

  

  

  

  Found. 
  

  

  Calc. 
  

  

  Found. 
  

  

  Calc. 
  

  

  

  

  SiO,-.. 
  

  

  

  37-24 
  

  

  37-14 
  

  

  

  37-49 
  

  

  37-64 
  

  

  

  

  BO 
  -. 
  

  

  

  9-95 
  

  

  38-66 
  

  

  5-49 
  

  

  10-83 
  

  

  38-07 
  

  

  5-24 
  

  

  

  10-32 
  

  

  39-86 
  

  

  3-74 
  

  

  10-97 
  

  

  39^04 
  

  

  3-61 
  

  

  

  

  FeO... 
  

  

  

  

  

  

  

  

  CaO 
  .. 
  

  

  

  •39 
  

  

  •35 
  

  

  

  -49 
  

  

  •46 
  

  

  

  

  Na 
  

  

  

  2-90 
  

   1-63 
  

  

  3-01 
  

  

  r64 
  

  

  

  2-59 
  

   1-71 
  

  

  2^76 
  

   1-69 
  

  

  

  

  Li,0 
  ., 
  

  

  

  

  

  HO 
  .. 
  

  

  

  3-74 
  

  

  3^72 
  

  

  

  3-80 
  

  

  3-83 
  

  

  

  

  •^3^ 
  — 
  

  

  

  

  100-00 
  100-00 
  

  

  100-00 
  

  

  100-00 
  

  

  In 
  these 
  cases 
  the 
  low 
  boric 
  acid 
  of 
  the 
  analyses, 
  and 
  the 
  

   uncertainties 
  as 
  to 
  the 
  significance 
  of 
  the 
  water 
  determinations, 
  

  

  