﻿48 
  Foote 
  and 
  Bradley 
  — 
  Constant 
  Composition 
  of 
  Alhite. 
  

  

  components, 
  the 
  latter 
  either 
  in 
  the 
  free 
  condition, 
  as 
  corun- 
  

   dum 
  or 
  silica, 
  or 
  in 
  combination, 
  as 
  nephelite. 
  These 
  associa- 
  

   tions 
  make 
  it 
  possible, 
  as 
  shown 
  above, 
  to 
  determine 
  with 
  

   some 
  definiteness 
  whether 
  solid 
  solution 
  occurs 
  between 
  albite 
  

   and 
  any 
  of 
  its 
  components, 
  and 
  if 
  so, 
  to 
  what 
  extent. 
  The 
  

   mineral 
  is 
  such 
  an 
  important 
  component 
  of 
  many 
  rocks 
  that 
  it 
  

   has 
  seemed 
  well 
  worth 
  while 
  to 
  investigate 
  this 
  problem. 
  

  

  Fortunately, 
  excellent 
  analyses 
  of 
  albite 
  associated 
  with 
  

   quartz 
  have 
  already 
  been 
  made. 
  These 
  minerals 
  occur 
  

   together, 
  beautifully 
  crystallized, 
  in 
  a 
  large 
  pegmatite 
  vein 
  at 
  

   Amelia 
  Court 
  House, 
  Ya., 
  and 
  an 
  analysis 
  of 
  the 
  albite 
  was 
  

   made 
  by 
  Musgrave 
  under 
  the 
  direction 
  of 
  Prof. 
  J. 
  W. 
  Mallett.* 
  

   Another 
  specimen 
  from 
  the 
  same 
  locality 
  was 
  analyzed 
  by 
  

   Robertson.! 
  Specimens 
  of 
  albite 
  from 
  this 
  locality 
  in 
  the 
  

   Brush 
  collection 
  show 
  quartz 
  intimately 
  associated 
  with 
  it, 
  but 
  

   in 
  neither 
  article 
  was 
  there 
  any 
  statement 
  of 
  the 
  association. 
  

   Professor 
  Mallett, 
  shortly 
  before 
  his 
  death, 
  however, 
  wrote 
  us 
  

   as 
  follows 
  regarding 
  the 
  occurrence 
  : 
  " 
  The 
  albite 
  you 
  refer 
  to 
  

   occurs 
  as 
  a 
  constituent 
  of 
  an 
  extremely 
  coarse-grained 
  granite 
  

   with 
  abundance 
  of 
  quartz. 
  The 
  feldspar 
  crystals 
  are 
  some- 
  

   times 
  more 
  than 
  two 
  feet 
  long 
  and 
  there 
  are 
  sheets 
  of 
  mica 
  

   twenty 
  inches 
  across." 
  The 
  analyses 
  of 
  this 
  albite 
  will 
  be 
  

   given 
  below. 
  

  

  The 
  occurrence 
  of 
  albite 
  with 
  corundum 
  is 
  much 
  more 
  

   uncommon. 
  An 
  analysis 
  of 
  this 
  type 
  of 
  albite 
  was 
  published 
  

   many 
  years 
  ago 
  by 
  Silliman.J 
  The 
  ratio 
  between 
  alkalies, 
  

   alumina 
  and 
  silica 
  was 
  1 
  : 
  1*16 
  : 
  6*04, 
  which 
  indicates 
  a 
  consider- 
  

   able 
  excess 
  of 
  alumina 
  above 
  the 
  theoretical 
  ratio, 
  but 
  the 
  

   analysis 
  was 
  made 
  before 
  heavy 
  solutions 
  were 
  in 
  use 
  and 
  the 
  

   material 
  was 
  presumably 
  not 
  as 
  pure 
  as 
  it 
  is 
  possible 
  to 
  obtain 
  

   at 
  present. 
  On 
  the 
  other 
  hand, 
  Moroscewicz§ 
  has 
  shown 
  

   that 
  artificial 
  fused 
  mixtures 
  of 
  albite 
  and 
  anorthite, 
  with 
  excess 
  

   of 
  alumina, 
  separate 
  the 
  latter 
  as 
  corundum 
  on 
  cooling, 
  but 
  his 
  

   results 
  hardly 
  prove 
  that 
  some 
  alumina 
  in 
  excess 
  may 
  not 
  be 
  

   retained 
  in 
  solid 
  solution. 
  

  

  We 
  have 
  been 
  able 
  to 
  obtain 
  but 
  one 
  specimen 
  of 
  a 
  rock 
  

   containing 
  both 
  albite 
  and 
  corundum. 
  This 
  was 
  a 
  corundum- 
  

   syenite 
  from 
  Brudenell, 
  Renfrew 
  Co., 
  Canada, 
  furnished 
  us 
  by 
  

   Prof. 
  L. 
  Y. 
  Pirsson. 
  It 
  also 
  contained 
  nephelite. 
  Preliminary 
  

   tests 
  showed 
  that 
  the 
  albite 
  contained 
  calcium, 
  indicating 
  the 
  

   presence 
  of 
  some 
  anorthite 
  in 
  solid 
  solution. 
  

  

  In 
  preparing 
  the 
  sample 
  for 
  analysis, 
  the 
  rock 
  was 
  crushed 
  

   and 
  albite 
  separated 
  by 
  hand 
  as 
  carefully 
  as 
  possible. 
  It 
  was 
  

   then 
  sifted 
  to 
  a 
  uniform 
  grain 
  and 
  put 
  through 
  a 
  heavy 
  solu- 
  

   tion. 
  On 
  account 
  of 
  their 
  higher 
  specific 
  gravity, 
  there 
  was 
  

   no 
  difficulty 
  whatever 
  in 
  separating 
  the 
  mica 
  and 
  corundum. 
  

  

  *Chem. 
  News, 
  xlvi, 
  204, 
  1882 
  f-Chem. 
  News, 
  1, 
  208, 
  1884. 
  

  

  {This 
  Journal, 
  viii, 
  390, 
  1849. 
  § 
  Min. 
  petr. 
  Mitt., 
  xviii, 
  1, 
  1898. 
  

  

  