﻿DEC. 
  4, 
  1922 
  WATSON 
  : 
  VEIN 
  OF 
  RUTILE-ILMENITE 
  453 
  

  

  Bearing 
  of 
  rutile-ilmenite 
  inter 
  growths 
  on 
  composition 
  of 
  r 
  utile. 
  — 
  This 
  

   subject 
  is 
  discussed 
  elsewhere 
  by 
  the 
  writer'^ 
  and 
  is 
  only 
  briefly 
  touched 
  

   on 
  here. 
  The 
  intergrowth 
  relations 
  of 
  the 
  two 
  titanium 
  minerals 
  de- 
  

   scribed 
  above 
  have 
  their 
  analogy 
  in 
  the 
  titaniferous 
  magnetites 
  which 
  

   have 
  been 
  shown 
  by 
  others 
  to 
  be 
  a 
  mechanical 
  mixture 
  of 
  ilmenite 
  in 
  

   the 
  host 
  magnetite. 
  

  

  All 
  modern 
  analyses 
  of 
  rutile 
  show 
  the 
  presence 
  of 
  ferrous 
  oxide 
  in 
  

   variable 
  amounts. 
  The 
  writer 
  suggests 
  that 
  probably 
  the 
  source 
  

   of 
  this 
  constituent 
  is 
  from 
  ilmenite 
  mechanically 
  mixed 
  with 
  rutile 
  

   and 
  not 
  from 
  a 
  supposed 
  isomorphous 
  mixture 
  of 
  ferroustitanate 
  

   (FeCTiOs)) 
  and 
  titanyl 
  titanate 
  (TiO)(Ti03), 
  as 
  has 
  been 
  advanced 
  

   by 
  some.^ 
  This 
  explanation 
  certainly 
  seems 
  applicable 
  to 
  the 
  rutile 
  

   of 
  the 
  Franklin 
  County, 
  Virginia, 
  vein. 
  Many 
  supposed 
  cases 
  of 
  

   isomorphism 
  among 
  sulphide 
  minerals 
  have 
  been 
  shown 
  by 
  modern 
  

   critical 
  study 
  to 
  represent 
  mechanical 
  mixtures.^ 
  The 
  writer 
  is 
  con- 
  

   vinced 
  that 
  this 
  relationship 
  holds 
  among 
  opaque 
  oxides, 
  

  

  CHEMICAI^ 
  COMPOSITION 
  OF 
  THE 
  RUTlI^E-IIvMENlTE 
  

  

  Chemical 
  analyses 
  of 
  the 
  rutile 
  and 
  rutile-ilmenite 
  from 
  the 
  Franklin 
  

   County, 
  Virginia, 
  rutile-bearing 
  quartz 
  vein 
  are 
  given 
  in 
  Table 
  I 
  

   below. 
  

  

  TABLE 
  I. 
  — 
  'Analyses 
  of 
  Rutile 
  and 
  Rutile-Ilmenite, 
  Franklin 
  County, 
  Virginia 
  

  

  Ti02 
  

  

  SiOo 
  

  

  CroOs 
  

  

  V2O3 
  : 
  

  

  FeO 
  

  

  MnO 
  

  

  HoO 
  _ 
  

  

  100.13 
  100.10 
  

  

  I. 
  Rutile, 
  Franklin 
  County, 
  Virginia. 
  William 
  M. 
  Thornton, 
  Jr., 
  analyst. 
  

  

  II. 
  Rutile-ilmenite, 
  Franklin 
  County, 
  Virginia. 
  Dorothy 
  Getz, 
  analyst. 
  

  

  The 
  possible 
  effect 
  of 
  the 
  presence 
  of 
  Cr203 
  and 
  V2O3 
  in 
  rutile, 
  as 
  

   shown 
  in 
  all 
  recent 
  accurate 
  analyses, 
  has 
  been 
  discussed 
  by 
  the 
  

  

  ' 
  Watson, 
  Thomas 
  L. 
  Rutile-ilmenite 
  intergrowths. 
  Amer. 
  Mineralogist. 
  1922. 
  (In 
  

   press.) 
  

  

  8 
  ScHALLER, 
  W. 
  T. 
  U. 
  S. 
  Geol. 
  Survey 
  Bull. 
  509: 
  9-39. 
  1912, 
  and 
  references. 
  

  

  9 
  Wherry, 
  E. 
  T. 
  This 
  Journal 
  10: 
  488. 
  1920. 
  Foshag, 
  W. 
  F. 
  Am. 
  J. 
  Sci. 
  1921. 
  

  

  