﻿F. 
  IF. 
  Charlie 
  — 
  Constitution 
  of 
  TourTnaline. 
  119 
  

  

  account 
  for 
  the 
  chief 
  variations 
  between 
  observation 
  and 
  theory. 
  

   There 
  is 
  another 
  complication 
  also, 
  due 
  to 
  the 
  fact 
  that 
  alterna- 
  

   tive 
  expressions 
  are 
  possible, 
  between 
  which 
  it 
  is 
  very 
  difficult 
  

   to 
  decide. 
  In 
  the 
  tourmaline 
  from 
  Haddam 
  JSTeck, 
  Conn., 
  

   analyzed 
  by 
  Penfield 
  and 
  Foote, 
  a 
  somewhat 
  different 
  com- 
  

   mingling 
  of 
  molecules 
  seems 
  to 
  be 
  necessary, 
  partly 
  on 
  account 
  

   of 
  the 
  higher 
  proportion 
  of 
  lime 
  in 
  the 
  mineral, 
  and 
  partly 
  on 
  

   account 
  of 
  the 
  fluorine. 
  This 
  tourmaline, 
  also, 
  admits 
  of 
  

   various 
  alternatives 
  in 
  formulation 
  ; 
  but 
  it 
  agrees 
  well 
  with 
  

   the 
  molecular 
  mixture 
  

  

  3. 
  Al.(SiO.)„(BO,),.BO,Ca.Fe.H,, 
  

  

  10. 
  AI,(SiO.),(BOJ,. 
  B03(A10H) 
  . 
  Al,Li,H„ 
  

  

  1. 
  Al.(SiO.).(BO,), 
  . 
  BO,Ca 
  . 
  Al.NaH,, 
  

  

  6. 
  Al,(SiO.),(BOJ, 
  . 
  BO.NaH 
  . 
  Al.NaH, 
  ; 
  

  

  in 
  which 
  Ca 
  is 
  equivalent 
  to 
  a 
  replacement 
  of 
  ^N'aH. 
  This 
  

   mixture, 
  with 
  the 
  group 
  AlOH 
  proportional 
  to 
  fluorine, 
  gives 
  

   a 
  good 
  comparison 
  between 
  analysis 
  and 
  theory, 
  thus 
  : 
  

  

  Found. 
  Reduced. 
  Calculated. 
  

  

  SiO, 
  36-96 
  36-75 
  36-86 
  

  

  B^Og 
  11-00 
  10-94 
  10-74 
  

  

  TiO, 
  -03 
  ) 
  

  

  Al,03 
  -. 
  _- 
  39-56 
  j 
  39-35 
  39-44 
  

  

  Feb 
  2-14 
  i 
  4-35 
  4-43 
  

  

  MnO 
  2-00 
  

  

  MgO 
  -15 
  

  

  CaO._ 
  1-28 
  1-27 
  1-15 
  

  

  Na^ 
  _-_ 
  2-10 
  2-09 
  2-07 
  

  

  Li„0 
  1-64 
  1-63 
  1-54 
  

  

  H,0 
  3-10 
  I 
  3-62 
  3-77 
  

  

  F 
  1-13 
  \ 
  

  

  101-09 
  100-00 
  100-00 
  

  

  The 
  theoretical 
  amount 
  of 
  fluorine 
  needed 
  to 
  replace 
  hydroxyl 
  

   in 
  the 
  assumed 
  group, 
  AlOH, 
  is 
  0-97 
  per 
  cent. 
  Altogether, 
  

   the 
  comparison 
  is 
  fairly 
  satisfactory. 
  

  

  One 
  analysis 
  by 
  Riggs, 
  that 
  of 
  the 
  magnesium 
  tourmaline 
  

   from 
  Hamburgh, 
  N. 
  J., 
  I 
  have 
  omitted 
  from 
  my 
  discussion. 
  

   In 
  that 
  tourmaline 
  there 
  are 
  variations 
  which 
  I 
  cannot 
  readily 
  

   account 
  for, 
  unless 
  by 
  assuming 
  the 
  presence 
  in 
  it 
  of 
  a 
  molecule 
  

  

  Al.(SiO.).(BOJ,.BO,R',.R", 
  

  

  Such 
  a 
  molecule, 
  written 
  structurally, 
  exhibits 
  affinities 
  to 
  

   garnet, 
  rather 
  than 
  to 
  the 
  micas 
  ; 
  and 
  I 
  prefer 
  to 
  await 
  further 
  

   evidence 
  before 
  committing 
  myself 
  to 
  any 
  definite 
  formulation 
  

   in 
  this 
  instance. 
  As 
  for 
  the 
  analyses 
  published 
  by 
  Jannasch 
  

  

  