﻿143 
  

  

  Finally, 
  to 
  complete 
  the 
  catalogue 
  of 
  identical 
  minerals, 
  M. 
  Staff 
  

   states 
  that 
  his 
  analysis 
  of 
  a 
  specimen 
  of 
  sillimanite 
  from 
  Chester, 
  Conn., 
  

   gives 
  the 
  formula 
  of 
  kyanite, 
  which 
  again 
  is 
  supposed 
  to 
  be 
  identical 
  

   with 
  the 
  disthene 
  of 
  Haiiy. 
  The 
  recent 
  analyses 
  of 
  Prof. 
  B. 
  Silliman, 
  

   Jun., 
  also 
  show 
  the 
  identity 
  of 
  sillimanite, 
  bucholzite 
  and 
  fibrolite, 
  with 
  

   kyanite. 
  Sill. 
  Jour., 
  Nov., 
  1849. 
  

  

  If 
  these 
  views 
  are 
  correct, 
  the 
  following 
  minerals 
  should 
  be 
  reduced 
  

   to 
  one 
  species, 
  viz 
  : 
  

  

  Bucholzite, 
  Andalusite, 
  

  

  Sillimanite, 
  Kyanite, 
  

  

  Xenolite, 
  Disthene. 
  

  

  Fibrolite, 
  

   Sillimanite 
  has 
  been 
  found 
  in 
  the 
  town 
  of 
  Yorktown, 
  Westchester 
  

   county, 
  about 
  ten 
  miles 
  north-east 
  of 
  Sing-Sing, 
  near 
  the 
  road 
  leading 
  

   from 
  Pine's 
  brige 
  to 
  Yorktown 
  post 
  office, 
  associated, 
  with 
  monazite, 
  

   tremolite 
  and 
  magnetic 
  iron. 
  The 
  crystals 
  are 
  distinct 
  and 
  run 
  through 
  

   the 
  iron 
  ore 
  ; 
  they 
  are 
  often 
  6 
  or 
  more 
  inches 
  in 
  length, 
  much 
  bent 
  and 
  

   fractured, 
  as 
  they 
  are 
  at 
  Norwich 
  and 
  Chester, 
  Con. 
  (Sill. 
  Jour, 
  xlvi, 
  

   p. 
  207.) 
  I 
  have 
  received 
  specimens 
  from 
  my 
  friend, 
  Mr. 
  Cyrus 
  P. 
  

   Fountain, 
  of 
  Peekskill. 
  

  

  According 
  to 
  the 
  analysis 
  of 
  Prof. 
  Norton, 
  of 
  Yale 
  College, 
  the 
  

   Yorktown 
  sillimanite 
  contains, 
  

  

  Silica, 
  37-70 
  

  

  Alumina, 
  ------- 
  62'75 
  

  

  Oxide 
  of 
  iron, 
  - 
  - 
  - 
  - 
  ' 
  - 
  - 
  2-29 
  

  

  10274 
  

  

  (Dana's 
  Mineralogy, 
  2d 
  ed., 
  p. 
  378.) 
  

  

  PITCHSTONE. 
  

   (Mineralogy 
  of 
  New- 
  York, 
  page 
  367.) 
  

  

  This 
  is 
  perhaps 
  the 
  most 
  appropriate 
  place 
  for 
  the 
  introduction 
  of 
  a 
  

   notice 
  of 
  a 
  mineral 
  found 
  by 
  Dr. 
  Emmons 
  at 
  Johnsburg, 
  in 
  Warren 
  

   county. 
  It 
  is 
  called 
  obsidian, 
  and 
  is 
  described 
  as 
  occurring 
  in 
  a 
  trap 
  

   dyke 
  at 
  the 
  line 
  of 
  contract 
  of 
  the 
  gneiss, 
  in 
  which 
  it 
  is 
  embraced. 
  

   The 
  mineral 
  has 
  a 
  bluish 
  black 
  color, 
  a 
  vitreous 
  lustre 
  and 
  a 
  conchoidal 
  

   fracture. 
  It 
  is 
  only 
  about 
  an 
  inch 
  wide 
  on 
  both 
  sides 
  of 
  the 
  dyke. 
  Dr. 
  

   Emmons 
  says, 
  " 
  it 
  is 
  to 
  be 
  considered 
  as 
  a 
  part 
  of 
  the 
  dyke, 
  which 
  for 
  

   some 
  cause 
  was 
  more 
  perfectly 
  pure, 
  and 
  in 
  consequence 
  of 
  more 
  sud- 
  

  

  