﻿52 
  Washington 
  — 
  Analyses 
  of 
  Italian 
  Volcanic 
  Rocks. 
  

  

  sections 
  showed 
  that 
  it 
  was 
  to 
  be 
  expected. 
  In 
  their 
  general 
  

   features 
  they 
  resemble 
  analyses 
  of 
  andesites, 
  though 
  possibly 
  

   somewhat 
  basic, 
  and 
  in 
  this 
  way 
  approaching 
  the 
  basalts. 
  It 
  

   has 
  been 
  noted 
  also 
  that 
  olivine 
  is 
  rare. 
  The 
  alkalies 
  amount 
  

   to 
  somewhat 
  more 
  than 
  five 
  per 
  cent, 
  and 
  K 
  2 
  molecularly 
  is 
  

   higher 
  than 
  JNa 
  2 
  0, 
  though 
  not 
  as 
  much 
  so 
  as 
  in 
  most 
  other 
  

   Italian 
  rocks. 
  The 
  analyses 
  do 
  not 
  differ 
  radically 
  from 
  the 
  

   older 
  ones 
  of 
  vom 
  Rath 
  and 
  Ricciardi, 
  which 
  are 
  given 
  for 
  

   comparison. 
  The 
  large 
  amount 
  of 
  S0 
  3 
  in 
  Ricciardi's 
  analyses 
  

   is 
  surprising, 
  since 
  no 
  noselite 
  could 
  be 
  found. 
  

  

  I 
  II 
  III 
  iv 
  v 
  

  

  Si0 
  2 
  54-14 
  54-56 
  55'00 
  53*63 
  55'23 
  

  

  TiO, 
  1-23 
  1-10 
  

  

  A1 
  2 
  3 
  16-42 
  16-49 
  14*38 
  14*17 
  14*06 
  

  

  Fe 
  2 
  3 
  1-69 
  1-02 
  ,__. 
  1-46 
  5*0,6 
  

  

  FeO 
  5*26 
  5*65 
  9*29 
  8*07 
  4*12 
  

  

  MnO 
  trace 
  trace 
  trace 
  0*57 
  

  

  MgO 
  8*44 
  8-57 
  7*72 
  7*05 
  4*00 
  

  

  CaO 
  8*05 
  7*95 
  8 
  51 
  8*52 
  9*34 
  

  

  Na 
  2 
  2-20 
  2*07 
  2*25 
  1*80 
  2*07 
  

  

  K 
  2 
  G 
  3*34 
  3-35 
  252 
  2*03 
  2*43 
  

  

  H 
  2 
  G 
  0*56 
  0*15 
  0*48 
  2*01 
  1*07 
  

  

  P 
  2 
  5 
  __. 
  0*93 
  1*33 
  

  

  S0 
  o 
  0*62 
  0*84 
  

  

  101*33 
  

  

  100*91 
  100*15 
  100*29 
  100*12 
  

  

  I. 
  Andesite 
  (black), 
  near 
  Castle 
  Gate, 
  Radicofani. 
  Washington 
  

   anal. 
  

   II. 
  Andesite 
  (gray), 
  west 
  of 
  village, 
  Radicofani. 
  Washington 
  

   anal. 
  

  

  III. 
  Andesite 
  (gray), 
  Radicofani, 
  vom 
  Rath, 
  Zeit. 
  deut. 
  Geol. 
  

  

  Ges., 
  xvii, 
  p. 
  405, 
  1865. 
  

  

  IV. 
  Andesite 
  (black), 
  Radicofani. 
  Ricciardi 
  anal. 
  Mercalli, 
  Atti 
  

  

  Soc. 
  Ital. 
  Sc. 
  Nat., 
  xxx, 
  p. 
  4, 
  1887. 
  

   V. 
  Andesite 
  (gray), 
  Radicofani. 
  Ricciardi 
  anal. 
  Mercalli, 
  

   op. 
  cit., 
  p. 
  8. 
  

  

  I 
  previously* 
  expressed 
  the 
  opinion 
  that 
  these 
  rocks 
  were 
  

   probably 
  ciminites, 
  but 
  the 
  examination 
  and 
  analysis 
  of 
  the 
  

   specimens 
  collected 
  since 
  then, 
  the 
  results 
  of 
  which 
  have 
  just 
  

   been 
  given, 
  show 
  that 
  while 
  they 
  are 
  analogous 
  to 
  them 
  in 
  cer- 
  

   tain 
  particulars, 
  yet 
  that 
  they 
  should 
  properly 
  be 
  classed 
  with 
  

   the 
  andesites, 
  which, 
  as 
  well 
  as 
  the 
  basalts, 
  are 
  rarely 
  found 
  on 
  

   the 
  Italian 
  peninsula. 
  The 
  occurrence 
  is 
  of 
  interest 
  as 
  show- 
  

   ing 
  that 
  the 
  Italian 
  latites 
  may 
  shade 
  off 
  into 
  true 
  andesites 
  

   and 
  basalts, 
  as 
  well 
  as 
  into 
  basic 
  leucitic 
  rocks. 
  

  

  * 
  Jour. 
  Geol., 
  v, 
  p. 
  355, 
  1897. 
  

  

  