﻿F. 
  W. 
  Clarke 
  — 
  Constitution 
  of 
  Tourmaline. 
  113 
  

  

  tnrally 
  correlated. 
  The 
  subjoined 
  formulse 
  are 
  sufficient 
  to 
  

   make 
  this 
  point 
  clear 
  ; 
  and 
  to 
  render 
  the 
  splitting 
  up 
  of 
  tour- 
  

   maline, 
  its 
  alteration 
  into 
  mica, 
  somewhat 
  intelligible. 
  

  

  Al-SiO, 
  = 
  Al 
  

   "-^SiO,~Al 
  

  

  Muscovite 
  

  

  /SiO,^H3 
  

   Al-SiO,EEH3 
  

   "-SiO,=:Al-BO, 
  

  

  A1-B0„=H„ 
  

  

  ^SiO,= 
  Al-BO, 
  

   Al-SiO 
  =H3 
  

  

  ^SiO,EEEH3 
  

  

  The 
  Tourmaline 
  Acid. 
  

  

  In 
  the 
  acid, 
  two 
  hydrogen 
  atoms 
  are 
  nnited 
  with 
  the 
  ortho- 
  

   boric 
  group, 
  and 
  twelve 
  with 
  the 
  orthosilicate 
  portion 
  of 
  the 
  

   nucleus. 
  Hence, 
  to 
  avoid 
  repetition 
  of 
  the 
  structural 
  expres- 
  

   sion, 
  the 
  formula 
  may 
  be 
  condensed 
  into 
  a 
  linear 
  form 
  as 
  

   follows 
  : 
  

  

  Al.(SiO.),(BOJ,.BO.H,.H.„ 
  

  

  and 
  this 
  is 
  applicable 
  to 
  the 
  discussion 
  of 
  the 
  analyses. 
  For 
  

   example, 
  Riggs' 
  analysis 
  of 
  the 
  black 
  magnesium 
  tourmaline 
  

   from 
  Pierrepont, 
  N. 
  Y., 
  corresponds 
  to 
  the 
  following 
  molecular 
  

   mixture 
  : 
  

  

  13. 
  Al,(SiOJ.(BO,), 
  . 
  BO.Ca 
  . 
  iMg.H, 
  

  

  1. 
  Al.(SiOJ,(BOJ,.BO,Mg.Mg,H. 
  

  

  2. 
  Al,(SiO.).(BO,),.BO,Na,.Al,Na.H, 
  

  

  Comparing 
  this 
  with 
  the 
  analj-sis, 
  and 
  reducing 
  the 
  latter 
  by 
  

   union 
  of 
  hke 
  bases 
  and 
  recalculation 
  to 
  100 
  per 
  cent, 
  we 
  have 
  — 
  

  

  Found. 
  

  

  SiO. 
  

  

  35-61 
  

  

  bo; 
  

  

  . 
  ,..._ 
  10-15 
  

  

  Al,03 
  

  

  FeO 
  

  

  25-29 
  

  

  -44 
  

  

  Tio;: 
  

  

  -55 
  

  

  CaO 
  

  

  3-31 
  

  

  FeO 
  

  

  8-19 
  

  

  MgO 
  

  

  Na,0 
  

  

  KO 
  

  

  11-07 
  

  

  1-51 
  

  

  •20 
  

  

  HO 
  

  

  3-34 
  

  

  F 
  

  

  •27 
  

  

  

  

  Reduced. 
  

  

  Calculated 
  

  

  37-19 
  

  

  37^05 
  

  

  10^51 
  

  

  10-80 
  

  

  27^10 
  

  

  27-19 
  

  

  99-93 
  

  

  3-45 
  

  

  16-31 
  

   1-72 
  

  

  3-72 
  

   100-00 
  

  

  -3-40 
  

  

  16-28 
  

   1-74 
  

  

  3-54 
  

   100-00 
  

  

  