﻿Washington 
  — 
  Analyses 
  of 
  Italian 
  Volcanic 
  Rocks. 
  53 
  

  

  Leucitite, 
  Capo 
  cii 
  Bove, 
  Alb 
  an 
  Hills. 
  — 
  Of 
  the 
  well- 
  

   known 
  rocks 
  of 
  the 
  Alban 
  Hills 
  only 
  the 
  analyses 
  made 
  by 
  

   Bunsen 
  in 
  186 
  1 
  have 
  been 
  published.* 
  It 
  was, 
  therefore, 
  

   thought 
  advisable 
  to 
  make 
  a 
  new 
  analysis 
  of 
  one 
  of 
  these 
  

   rocks, 
  and 
  for 
  this 
  purpose 
  a 
  fresh 
  specimen 
  collected 
  at 
  the 
  

   quarries 
  at 
  Capo 
  di 
  Bove, 
  near 
  the 
  tomb 
  of 
  Cecilia 
  Metella, 
  

   was 
  selected. 
  The 
  rock, 
  a 
  flow 
  from 
  the 
  Alban 
  volcano, 
  is 
  the 
  

   well 
  known 
  one 
  which 
  is 
  found 
  in 
  all 
  collections, 
  and 
  does 
  not 
  

   call 
  for 
  a 
  lengthy 
  description. 
  It 
  need 
  only 
  be 
  said 
  that 
  this 
  

   specimen 
  is 
  composed 
  of 
  leucite, 
  melilite, 
  nephelite, 
  diopside, 
  

   magnetite, 
  a 
  few 
  flakes 
  of 
  biotite, 
  scarcely 
  any 
  apatite, 
  and 
  no 
  

   glass. 
  

  

  I 
  II 
  ill 
  

  

  Si0 
  o 
  . 
  _ 
  45-99 
  45-93 
  46'51 
  

  

  • 
  Ti0 
  2 
  ._ 
  0-37 
  0-83 
  

  

  Al 
  2 
  O 
  s 
  17*12 
  18-72 
  11-86 
  

  

  Fe 
  2 
  3 
  ... 
  4-17 
  7-59 
  

  

  FeO 
  5-38 
  10-68 
  4'39 
  

  

  MnO. 
  trace 
  0*22 
  

  

  MsO 
  5-30 
  5-67 
  4-73 
  

  

  CaO 
  ._ 
  10-47 
  10-57 
  7'41 
  

  

  BaO 
  0-25 
  0-50 
  

  

  SrO 
  ._ 
  none 
  0'16 
  

  

  Na 
  o 
  2-18 
  1-68 
  . 
  2-39 
  

  

  K 
  2 
  6 
  8-97 
  6-83 
  8'7l 
  

  

  H,O(110°)-) 
  nA 
  . 
  nKO 
  1-10 
  

  

  H;O(110 
  o 
  ) 
  + 
  \ 
  04 
  ° 
  °' 
  59 
  2-45 
  

  

  100-65 
  100-67 
  99-73f 
  

  

  I. 
  Leucitite, 
  Capo 
  di 
  Bove. 
  Washington 
  analyst. 
  

   II. 
  Leucitite, 
  Capo 
  di 
  Bove. 
  Bunsen 
  analyst. 
  Roth. 
  Beitr. 
  

   Petr., 
  1869, 
  p. 
  cii, 
  No. 
  31. 
  

   III. 
  Leucitite, 
  Bearpaw 
  Mountain, 
  Montana. 
  H. 
  N. 
  Stokes 
  anal. 
  

   Weed 
  and 
  Pirsson, 
  this 
  Journal, 
  ii, 
  p. 
  147, 
  1896. 
  

  

  The 
  analysis, 
  which 
  resembles 
  closely 
  the 
  older 
  one 
  of 
  

   Bunsen 
  (II), 
  except 
  as 
  to 
  A1 
  2 
  3 
  and 
  K 
  a 
  O, 
  is 
  characterized 
  by 
  

   high 
  K 
  2 
  0, 
  CaO 
  and 
  iron 
  oxides, 
  and, 
  for 
  so 
  basic 
  a 
  rock, 
  quite 
  

   high 
  A1 
  2 
  3 
  and 
  low 
  MgO. 
  It 
  was 
  thought 
  possible 
  that 
  the 
  

   same 
  error 
  had 
  been 
  made 
  in 
  the 
  determination 
  of 
  these 
  two 
  

   oxides 
  which 
  has 
  already 
  been 
  noticed 
  elsewhere. 
  So 
  a 
  second 
  

   analysis 
  was 
  made 
  recently, 
  which, 
  however, 
  gave 
  results 
  quite 
  

   confirmatory 
  of 
  those 
  of 
  the 
  earlier 
  one. 
  The 
  figures 
  given 
  

   above 
  are 
  the 
  means 
  of 
  the 
  two 
  closely 
  agreeing 
  determinations 
  

   of 
  all 
  the 
  constituents, 
  except 
  II 
  2 
  0. 
  They 
  may, 
  therefore, 
  be 
  

   considered 
  reliable. 
  

  

  * 
  Roth. 
  Beitr. 
  Petr. 
  plut. 
  Gest., 
  1869. 
  p. 
  cii, 
  Nos. 
  30-33. 
  

  

  .f 
  Including 
  80 
  P 
  2 
  5 
  , 
  0-04 
  CI, 
  04 
  NiO 
  and 
  traces 
  of 
  CuO, 
  CoO, 
  F 
  and 
  S0 
  3 
  . 
  

  

  