﻿478 
  F. 
  W. 
  Clarice 
  — 
  Constitution 
  of 
  Melilite 
  and 
  Gehlenite. 
  

  

  sarcolite, 
  while 
  gehlenite 
  contains 
  little 
  or 
  none. 
  Weinschenk's 
  

   fuggerite 
  is 
  an 
  exceptional 
  mineral, 
  lying 
  near 
  the 
  boundary 
  

   between 
  melilite 
  and 
  gehlenite, 
  and 
  showing 
  affinities 
  for 
  both 
  

   species. 
  It 
  is 
  best 
  classified 
  as 
  a 
  sodic 
  variety 
  of 
  gehlenite. 
  

  

  The 
  reported 
  syntheses 
  of 
  melilite 
  are 
  not 
  altogether 
  satis- 
  

   factory, 
  and 
  need 
  not 
  be 
  discussed 
  here. 
  There 
  are, 
  however, 
  

   melilites 
  of 
  artificial 
  origin 
  which 
  are 
  very 
  significant 
  as 
  

   regards 
  chemical 
  composition. 
  For 
  example, 
  the 
  melilite 
  crys- 
  

   tals 
  obtained 
  by 
  Bodlander* 
  from 
  Portland 
  cement, 
  have 
  very 
  

   nearly 
  the 
  composition 
  represented 
  by 
  the 
  formula 
  Al 
  9 
  (Si0 
  4 
  ) 
  6 
  

   Ca 
  6 
  Mg 
  3 
  ; 
  which 
  may 
  be 
  written 
  structurally 
  thus 
  : 
  

  

  / 
  Si0 
  4 
  = 
  Ca 
  3 
  = 
  Si0 
  4 
  \ 
  

  

  Al 
  — 
  Si0 
  4 
  = 
  Ca 
  3 
  = 
  Si0 
  4 
  — 
  Al 
  

   \Si0 
  4 
  EEMg 
  3 
  = 
  Si0 
  4 
  / 
  

  

  Another 
  crystalline 
  melilite 
  isolated 
  by 
  Stahlf 
  from 
  furnace 
  

   slag 
  has 
  very 
  nearly 
  the 
  same 
  molecular 
  ratios. 
  In 
  this 
  in- 
  

   stance, 
  however, 
  the 
  general 
  formula 
  Al 
  2 
  (Si0 
  4 
  ) 
  6 
  R 
  9 
  // 
  includes 
  a 
  

   large 
  proportion 
  of 
  ferrous 
  iron 
  and 
  some 
  zinc 
  among 
  the 
  com- 
  

   ponents 
  of 
  R. 
  With 
  these 
  clues 
  we 
  may 
  write 
  the 
  following 
  

   series 
  of 
  formulae 
  : 
  

  

  Al 
  6 
  (Si0 
  4 
  ) 
  6 
  Ca 
  3 
  , 
  Aoorthite. 
  

   Al 
  4 
  (Si0 
  4 
  ) 
  6 
  Ca 
  6 
  , 
  Garnet 
  (and 
  sarcolite). 
  

   Al 
  2 
  (Si0 
  4 
  ) 
  6 
  Ca 
  9 
  , 
  In 
  melilite. 
  

  

  These 
  expressions 
  are 
  to 
  be 
  qualified 
  by 
  the 
  evident 
  fact 
  that 
  

   in 
  melilite 
  as 
  in 
  garnet 
  ferric 
  molecules 
  may 
  be 
  commingled 
  

   with 
  those 
  of 
  alumina, 
  and 
  ferrous 
  or 
  magnesian 
  molecules 
  

   with 
  those 
  of 
  lime. 
  In 
  natural 
  melilite 
  we 
  have, 
  apparently, 
  a 
  

   crystalline 
  mixture 
  of 
  the 
  normal 
  melilite, 
  as 
  written 
  above, 
  

   with 
  sarcolite, 
  soda 
  sarcolite, 
  and 
  a 
  small 
  proportion 
  of 
  a 
  tri- 
  

   silicate, 
  Al 
  4 
  (Si 
  3 
  8 
  ) 
  6 
  Ca 
  4 
  Na 
  4 
  , 
  equivalent 
  to 
  sarcolite. 
  A 
  study 
  of 
  

   the 
  available 
  analyses 
  of 
  melilite 
  will 
  serve 
  to 
  show 
  how 
  closely 
  

   this 
  scheme 
  fits 
  the 
  facts. 
  

  

  Analyses 
  of 
  Melilite 
  

  

  1. 
  Daraour 
  analyst. 
  From 
  Vesuvius. 
  

  

  Capo 
  di 
  Bove, 
  yellow. 
  

   " 
  " 
  brown. 
  

  

  u 
  it 
  

  

  " 
  " 
  yellow. 
  

  

  " 
  " 
  • 
  brown. 
  

  

  Iron 
  Hill, 
  Uncompahgre 
  quad- 
  

   rangle, 
  Colorado.]; 
  

  

  *Neues 
  Jabrb., 
  1892, 
  vol. 
  i, 
  p. 
  53. 
  

  

  f 
  Berg-u.-Huttenmanniscbe 
  Zeitung, 
  lxiii, 
  273, 
  1904. 
  Discussed 
  by 
  Zam- 
  

   bonini 
  in 
  Zeitschr. 
  Kryst., 
  xli, 
  226, 
  1906. 
  

  

  t 
  See 
  Larsen 
  and 
  Scballer, 
  Journ. 
  Wasb. 
  Acad., 
  iv, 
  473, 
  1914. 
  

  

  2. 
  

  

  a 
  u 
  

  

  3. 
  

  

  a 
  a 
  

  

  4. 
  

  

  Bodlander 
  " 
  

  

  5. 
  

  

  Zambonini 
  " 
  

  

  6. 
  

  

  a 
  a 
  

  

  t 
  . 
  

  

  Schaller 
  " 
  

  

  