﻿42 
  

  

  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Thus, 
  according 
  to 
  the 
  old 
  qualitative 
  classification, 
  the 
  rock 
  is 
  a 
  

   biotite-diabase, 
  while 
  under 
  the 
  new 
  quantitative 
  chemical 
  classifica- 
  

   tion 
  it 
  is 
  a 
  biotite-camptonose. 
  The 
  amounts 
  of 
  Si0 
  2 
  , 
  A1 
  2 
  3 
  , 
  and 
  

   CaO 
  in 
  the 
  analysis 
  strongly 
  bear 
  out 
  the 
  determination 
  of 
  the 
  

   plagioclase 
  as 
  ranging 
  from 
  andesine 
  to 
  labradorite. 
  Such 
  a 
  high 
  

   content 
  of 
  FeO 
  in 
  the 
  analysis 
  makes 
  it 
  certain 
  that 
  the 
  biotite 
  is 
  

   rich 
  in 
  ferrous 
  iron, 
  since 
  there 
  is 
  not 
  enough 
  magnetite 
  and 
  augite 
  

   to 
  account 
  for 
  so 
  much 
  FeO. 
  The 
  sulphur 
  appears 
  too 
  low 
  as 
  judged 
  

   by 
  the 
  amount 
  of 
  pyrite 
  visible 
  even 
  to 
  the 
  naked 
  eye. 
  The 
  high 
  

   Ti0 
  2 
  shows 
  either 
  ilmenite 
  or 
  that 
  the 
  magnetite 
  is 
  decidedly 
  titan- 
  

   iferous, 
  though 
  a 
  little 
  of 
  the 
  Ti0 
  2 
  may 
  be 
  in 
  the 
  biotite. 
  The 
  low 
  

   Fe 
  2 
  3 
  content 
  in 
  the 
  analysis 
  favors 
  the 
  presence 
  of 
  ilmenite. 
  

  

  It 
  is 
  important 
  to 
  note 
  that 
  the 
  analyses 
  of 
  the 
  diabase 
  and 
  typical 
  

   gabbro 
  are 
  very 
  similar 
  except 
  for 
  somewhat 
  higher 
  silica 
  and 
  lower 
  

   lime 
  in 
  the 
  diabase, 
  this 
  difference 
  probably 
  being 
  due 
  to 
  the 
  slightly 
  

   more 
  acid 
  character 
  of 
  the 
  plagioclase 
  in 
  the 
  diabase. 
  Thus 
  the 
  

   two 
  rocks 
  have 
  quite 
  certainly 
  been 
  derived 
  from 
  the 
  same 
  source 
  

   of 
  basic 
  supply 
  though 
  at 
  different 
  times. 
  

  

  Table 
  12 
  

   Adirondack 
  diabase 
  analyses 
  compared 
  

  

  Si02 
  

  

  50.57 
  

   13-58 
  

   3.26 
  

   10.09 
  

   4.98 
  

   7-67 
  

   2.92 
  

   1.89 
  

   1 
  . 
  10 
  

  

  M203 
  

  

  Fe 
  2 
  3 
  

  

  FeO 
  ; 
  

  

  MgO 
  

  

  CaO 
  

  

  Na 
  2 
  

  

  K2O 
  

  

  H2O 
  

  

  Ti0 
  2 
  

  

  2.68 
  

  

  P2O5 
  

  

  .28 
  

  

  CI 
  

  

  .09 
  

   .09 
  

  

  ".'36 
  

   .09 
  

   . 
  10 
  

  

  F 
  

  

  Cr 
  2 
  3 
  

  

  MnO.... 
  

  

  BaO 
  

  

  SrO 
  

  

  S 
  

  

  •03 
  

  

  CO2 
  

  

  99.78 
  

  

  2.00 
  

  

  too. 
  54 
  

  

  44-51 
  

   19.99 
  

  

  7.22 
  

   8. 
  11 
  

   8-15 
  

   5-24 
  

   2.60 
  

  

  2-93 
  

  

  45 
  46 
  

   19.94 
  

  

  I5-36 
  

  

  2-95 
  

   8.32 
  

   2. 
  12 
  

   3.21 
  

   2.30 
  

  

  98.75 
  

  

  99.66 
  

  

  46.73 
  

   16.66 
  

  

  3-56 
  

  

  8-45 
  

   8.12 
  

   8.03 
  

  

  3-73 
  

   1 
  .64 
  

  

  2-39 
  

   ■03 
  

   •39 
  

   .18 
  

   .26 
  

   .06 
  

   trace 
  

   .04 
  

  

  100.27 
  

  

  50.89 
  

   15-39 
  

  

  5-77 
  

   7.60 
  

   8-75 
  

   5-67 
  

   2.72 
  

   2.46 
  

  

  99 
  25 
  

  

  