﻿Washington 
  — 
  Analyses 
  of 
  Italian 
  Volcanic 
  Rocks. 
  47 
  

  

  feldspar 
  and 
  oligoclase. 
  The 
  amount 
  of 
  lime 
  found 
  on 
  analysis 
  

   indicates 
  that 
  the 
  latter 
  is 
  present 
  in 
  considerable 
  quantity. 
  

   The 
  feldspars 
  are 
  frequently 
  branched 
  and 
  tend 
  to 
  assume 
  

   kerannoidal 
  forms. 
  This 
  is 
  especially 
  well 
  seen 
  in 
  specimens 
  

   near 
  the 
  contact 
  with 
  the 
  marls, 
  in 
  which, 
  although 
  much 
  

   decomposed, 
  the 
  branching 
  of 
  the 
  feldspars 
  (here 
  more 
  slender) 
  

   is 
  well 
  developed. 
  A 
  few 
  stout 
  irregular 
  grains 
  of 
  quartz 
  

   (apparently 
  secondary) 
  and 
  small 
  apatites 
  and 
  magnetites 
  are 
  

   present, 
  but 
  are 
  not 
  common. 
  Scarcely 
  any 
  true 
  glass 
  could 
  

   be 
  made 
  out 
  with 
  certainty. 
  

  

  Even 
  the 
  freshest 
  specimens 
  from 
  newly 
  quarried 
  large 
  

   blocks 
  are 
  somewhat 
  decomposed, 
  since 
  the 
  olivines 
  are 
  all 
  

   entirely 
  altered 
  to 
  pilite, 
  but 
  the 
  diopside, 
  the 
  feldspars, 
  and 
  

   apparently 
  the 
  biotite, 
  are 
  quite 
  unaltered, 
  so 
  that 
  it 
  is 
  prob- 
  

   able 
  that 
  the 
  analysis 
  represents 
  very 
  well 
  the 
  composition 
  of 
  

   the 
  fresh 
  rock. 
  This, 
  made 
  on 
  the 
  freshest 
  piece 
  obtainable 
  at 
  

   the 
  quarry 
  of 
  Signor 
  Ireneo 
  Capelli, 
  is 
  given 
  in 
  I. 
  

  

  I 
  II 
  III 
  IV 
  V 
  VI 
  YII 
  VIII 
  

  

  SiOo 
  56-39 
  55 
  69 
  56-19 
  58 
  21 
  41-43 
  53'70 
  57*37 
  5517 
  

  

  Ti0 
  2 
  2 
  07 
  trace 
  069 
  trace 
  029 
  1-92 
  

  

  AI063--- 
  12-88 
  19-08 
  1676 
  19 
  90 
  9"80 
  11-16 
  13-84 
  13-49 
  

  

  Fe 
  2 
  3 
  2-36 
  407 
  305 
  4"07 
  3"28 
  340 
  2'44 
  3'10 
  

  

  FeO. 
  3-54 
  3-26 
  4-18 
  087 
  5 
  15 
  121 
  3"44 
  3"55 
  

  

  MnO 
  trace 
  trace 
  0-10 
  trace 
  0*04 
  trace 
  39 
  

  

  MgO 
  783 
  3-41 
  3-79 
  0-98 
  13-40 
  644 
  6 
  05 
  8'55 
  

  

  CaO 
  4 
  06 
  6-87 
  6-53 
  3'58 
  16 
  62 
  3-46 
  5'53 
  3'15 
  

  

  Xa 
  2 
  130 
  2 
  89 
  2 
  53 
  2-57 
  164 
  1'67 
  1-53 
  4*43 
  

  

  K.O 
  7 
  84 
  4-41 
  4-46 
  9-17 
  7 
  40 
  11-16 
  4'47 
  1-09 
  

  

  H 
  a 
  O(ll0 
  3 
  -) 
  ) 
  ,.33 
  ., 
  7 
  0-34 
  0-80 
  

  

  H 
  2 
  O(110° 
  + 
  ) 
  \ 
  lod 
  U 
  l1 
  0-66 
  U 
  ' 
  4 
  1Ll 
  2-61 
  d17 
  4J7 
  

  

  P 
  2 
  5 
  0-55 
  none 
  1-75* 
  0'37 
  

  

  C0 
  2 
  0-67 
  3-27 
  

  

  99-60 
  99-85 
  100-02* 
  10009 
  100-12 
  100'40f 
  10001^ 
  100'46 
  

  

  I. 
  Selagite 
  ( 
  <; 
  Mica-trachyte 
  "), 
  Monte 
  Catini, 
  Tuscany. 
  Washington 
  anal. 
  

   II. 
  Biotite-vulsinite, 
  Monte 
  Santa 
  Croce, 
  Rocca 
  Monfina. 
  Washington 
  anal. 
  

   Jour. 
  Geol., 
  v, 
  p. 
  252, 
  1897. 
  

  

  III. 
  Augite-latite, 
  Tahle 
  Mountain, 
  Sierra 
  Nevada, 
  Cal. 
  Hillebrand 
  anal. 
  

  

  Turner, 
  14th 
  Ann. 
  Rep. 
  U. 
  S. 
  G. 
  S., 
  p. 
  491, 
  1894. 
  

  

  IV. 
  Vulsinite, 
  Bolsena, 
  Washington 
  anal. 
  Jour. 
  Geo!., 
  iv, 
  p. 
  552, 
  1896. 
  

   V. 
  Venanzite. 
  San 
  Venanzo. 
  Umbria, 
  Rosenbusch, 
  op. 
  cit. 
  infra., 
  p. 
  113. 
  

  

  VI. 
  Wvomingite, 
  Leucite 
  Hills. 
  Hillebrand 
  anal. 
  Cross, 
  this 
  Journal, 
  iv. 
  

   p. 
  130, 
  1897. 
  

   VII. 
  Minette. 
  Kirschhauser 
  Thai. 
  Odenwald, 
  Lcpsius 
  in 
  Zirkel, 
  Lehrbuch, 
  ii, 
  

  

  p. 
  349, 
  1894. 
  

   VIII. 
  Verite, 
  Osann 
  anal., 
  Zeit. 
  deut. 
  Geol. 
  Ges., 
  xli, 
  p. 
  311, 
  1889. 
  

  

  The 
  noteworthy 
  features 
  of 
  this 
  are 
  the 
  medium 
  Si0 
  2 
  , 
  high 
  

   Mg< 
  ). 
  K 
  2 
  and 
  Ti0 
  2 
  , 
  moderate 
  CaO 
  and 
  low 
  A1 
  2 
  3 
  and 
  Na 
  a 
  O. 
  

   Its 
  essentially 
  monzonitic 
  or 
  latitic 
  character, 
  and 
  the 
  resem- 
  

  

  * 
  Including 
  0-19 
  BaO 
  and 
  trace 
  of 
  SrO. 
  

  

  t 
  Including 
  04 
  Cr 
  2 
  3 
  , 
  0-62 
  BaO, 
  0-19 
  SrO, 
  0'06 
  S0 
  3 
  , 
  03 
  CI, 
  and 
  044 
  F. 
  

  

  + 
  Including 
  T13 
  FeS 
  2 
  and 
  trace 
  S0 
  3 
  . 
  

  

  