﻿284: 
  Phillips 
  — 
  Mineralogical 
  Structure 
  and 
  Chemical 
  

  

  Here 
  the 
  normal 
  feldspar 
  is 
  an 
  andesine 
  or 
  oligoclase, 
  replac- 
  

   ing 
  the 
  normal 
  labradorite 
  of 
  quarrj 
  No. 
  2. 
  In 
  order 
  to 
  get 
  

   an 
  estimate 
  of 
  the 
  quantity 
  of 
  each 
  mineral 
  compound 
  of 
  

   quarry 
  ^o. 
  2 
  and 
  No. 
  3, 
  a 
  sample 
  of 
  each 
  was 
  taken, 
  crushed 
  

   finer 
  than 
  y^-^ 
  inch, 
  and 
  the 
  dust 
  washed 
  out, 
  then 
  separated 
  

   wdth 
  the 
  magnet 
  and 
  solution, 
  with 
  the 
  following 
  results, 
  as 
  

   the 
  magnet 
  was 
  strong 
  enough 
  to 
  remove 
  the 
  secondary 
  oxide 
  

   of 
  iron 
  granules 
  formed 
  by 
  the 
  decomposition 
  of 
  diallage 
  : 
  in 
  

   getting 
  the 
  total 
  per 
  cent 
  of 
  diallage 
  this 
  magnetic 
  portion 
  

   must 
  be 
  considered, 
  but 
  is 
  given 
  separately 
  here. 
  

  

  Quarry 
  No. 
  2. 
  Quarry 
  No. 
  3. 
  

  

  Magnetite 
  41 
  6- 
  

  

  Magnetic 
  3-6 
  9*7 
  

  

  Diallage 
  45-6 
  41* 
  

  

  Feldspar, 
  G. 
  > 
  2-69 
  32"2 
  23-1 
  

  

  Feldspar, 
  G. 
  < 
  2-69 
  14-3 
  •13-4 
  

  

  Feldspar, 
  G. 
  < 
  2-60- 
  _ 
  0- 
  6-5 
  

  

  The 
  decrease 
  in 
  the 
  density 
  of 
  the 
  feldspars 
  from 
  No. 
  2 
  to 
  

   No. 
  3, 
  or 
  their 
  increase 
  in 
  acidity 
  is 
  clearly 
  shown 
  by 
  the 
  above 
  

   figures. 
  The 
  total 
  feldspars 
  in 
  No. 
  2 
  is 
  45 
  per 
  cent 
  ; 
  69 
  per 
  

   cent 
  of 
  this 
  is 
  denser 
  than 
  2*69, 
  and 
  31 
  per 
  cent 
  lighter 
  than 
  

   2-69, 
  while 
  it 
  all 
  falls 
  before 
  the 
  solution 
  reaches 
  the 
  density 
  

   of 
  2-60. 
  The 
  total 
  feldspars 
  in 
  No. 
  3 
  is 
  43 
  per 
  cent, 
  53*7 
  per 
  

   cent 
  is 
  denser 
  than 
  2*69, 
  and 
  46*3 
  per 
  cent 
  below 
  the 
  density 
  

   of 
  2-69 
  ; 
  of 
  this 
  67*3 
  per 
  cent 
  is 
  denser 
  than 
  2-60, 
  while 
  32-Y 
  

   per 
  cent 
  is 
  below 
  the 
  gravity 
  of 
  2' 
  60. 
  

  

  In 
  the 
  crystallization 
  of 
  the 
  feldspars, 
  the 
  tendency 
  is 
  to 
  form 
  

   the 
  anorthite 
  molecule 
  at 
  the 
  border 
  region, 
  but 
  that 
  has 
  not 
  

   been 
  reached, 
  as 
  the 
  optical 
  properties 
  of 
  the 
  crystals 
  in 
  this 
  

   region 
  are 
  those 
  of 
  a 
  feldspar 
  of 
  the 
  composition 
  of 
  bytownite, 
  

   a 
  feldspar 
  richer 
  in 
  CaO 
  than 
  any 
  of 
  the 
  samples 
  analyzed 
  ; 
  

   this 
  is 
  also 
  substantiated, 
  as 
  the 
  analyses 
  of 
  the 
  rock 
  in 
  this 
  

   •region 
  indicates 
  a 
  10 
  per 
  cent 
  increase 
  in 
  CaO. 
  From 
  the 
  

   bytownite 
  molecule 
  the 
  amount 
  of 
  CaO 
  has 
  gradually 
  decreased 
  

   until 
  in 
  quarry 
  No. 
  3, 
  the 
  last 
  region 
  to 
  consolidate, 
  a 
  feldspar 
  

   almost 
  free 
  of 
  CaO 
  has 
  been 
  formed, 
  with 
  a 
  large 
  percentage 
  of 
  

   Kfi. 
  Thus 
  the 
  feldspars 
  of 
  the 
  Rocky 
  Hill 
  dike 
  present 
  a 
  

   complexity 
  far 
  greater 
  than 
  has 
  jQi 
  been 
  noted 
  in 
  connection 
  

   with 
  the 
  Mesozoic 
  trap. 
  

  

  Conclusion. 
  

  

  1st. 
  The 
  Rocky 
  Hill 
  trap, 
  from 
  its 
  holocrystalline 
  nature, 
  

   would 
  be 
  classed 
  as 
  a 
  dolerite. 
  

  

  2d. 
  The 
  border 
  region 
  possesses 
  the 
  ophitic 
  development 
  

   of 
  its 
  plagioclase 
  ; 
  if 
  the 
  small 
  amount 
  of 
  olivine 
  present 
  be 
  

   considered, 
  it 
  would 
  present 
  the 
  structure 
  and 
  composition 
  of 
  

   an 
  olivine 
  diabase. 
  

  

  