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  136 
  

  

  replacement 
  of 
  the 
  constituents 
  of 
  certain 
  minerals, 
  the 
  crystalline 
  forms 
  

   of 
  which 
  remain 
  the 
  same. 
  See 
  Memoirs 
  Bost. 
  Nat. 
  Hist. 
  Soc.,ii., 
  p. 
  SS 
  

  

  (Mineralogy 
  of 
  New- 
  York, 
  page 
  320.) 
  

  

  Hermann, 
  of 
  St. 
  Petersburgh, 
  has 
  announced 
  that 
  the 
  constitution 
  of 
  

   gibbsite 
  was 
  that 
  of 
  a 
  hydrous 
  phosphate 
  of 
  alumina, 
  and 
  that 
  the 
  com- 
  

   position 
  assigned 
  to 
  gibbsite 
  by 
  Torrey, 
  belonged 
  only 
  to 
  the 
  hydrargil- 
  

   lite 
  of 
  Rose. 
  Prof. 
  B. 
  Silliman, 
  Jr., 
  has 
  repeated 
  the 
  analysis 
  of 
  this 
  

   mineral, 
  from 
  Richmond, 
  Mass 
  , 
  and 
  finds 
  it 
  to 
  correspond 
  to 
  the 
  formula 
  

   first 
  given, 
  which 
  requires 
  : 
  

  

  Alumina, 
  ------- 
  65-800 
  

  

  Water, 
  34-200 
  

  

  100-000 
  

   And 
  the 
  mean 
  results 
  of 
  his 
  analysis 
  correspond 
  very 
  closely 
  to 
  the 
  

   calculated 
  per 
  centages. 
  The 
  phosphoric 
  acid 
  is 
  like 
  the 
  magnesia, 
  iron 
  

   and 
  silica, 
  contained 
  in 
  gibbsite, 
  only 
  as 
  a 
  contingent 
  impurity. 
  The 
  

   gibbsite, 
  he 
  says, 
  is 
  sometimes 
  mixed 
  with 
  allophane, 
  which 
  will 
  account 
  

   for 
  the 
  presence 
  of 
  silica 
  ; 
  and 
  he 
  thinks 
  the 
  silica 
  mentioned 
  by 
  Dr. 
  

   T. 
  Thompson, 
  in 
  his 
  analysis, 
  was 
  derived 
  from 
  the 
  same 
  intermixture 
  

   of 
  the 
  two 
  species. 
  There 
  is 
  now 
  little 
  doubt 
  that 
  the 
  hydrargillite 
  of 
  

   Rose, 
  and 
  gibbsite, 
  are 
  identical 
  ; 
  the 
  former 
  is 
  the 
  crystalline, 
  the 
  lat- 
  

   ter 
  the 
  amorphous 
  variety 
  of 
  the 
  same 
  species. 
  Sill. 
  Jour., 
  July, 
  1849 
  

   ■page 
  411. 
  

  

  (Mineralogy 
  of 
  New-York, 
  page 
  321.) 
  

  

  Subsequent 
  examination 
  has 
  satisfied 
  me 
  that 
  the 
  mineral 
  called 
  ido- 
  

   crase, 
  from 
  Hall's, 
  on 
  Muscolunge 
  lake, 
  in 
  Jefferson 
  county, 
  is 
  pyroxene. 
  

   The 
  measurement 
  of 
  the 
  primary 
  is, 
  as 
  nearly 
  as 
  can 
  be 
  determined, 
  

   87° 
  and 
  93° 
  ; 
  the 
  replacing 
  planes, 
  134°. 
  Its 
  color, 
  although 
  peculiar, 
  

   is 
  not 
  unlike 
  that 
  of 
  the 
  pyroxene 
  found 
  on 
  the 
  Rossie 
  turnpike, 
  two 
  

   miles 
  from 
  the 
  village 
  of 
  Oxbow, 
  in 
  Jefferson 
  county. 
  

  

  (Mineralogy 
  of 
  New- 
  York, 
  page 
  323.) 
  

  

  The 
  variety 
  colophonite, 
  is 
  reported 
  by 
  Dr. 
  Emmons 
  as 
  being 
  abun- 
  

   dant 
  at 
  Johnsburg, 
  Warren 
  county. 
  Rep. 
  on 
  the 
  Gcol. 
  2d 
  Dist., 
  p. 
  192 
  

  

  