﻿138 
  

  

  (Mineralogy 
  of 
  New- 
  York, 
  page 
  334.) 
  

  

  The 
  recent 
  researches 
  of 
  Erdmann, 
  in 
  regard 
  to 
  this 
  mineral, 
  deserve 
  

   to 
  be 
  noticed. 
  The 
  following 
  abstract 
  is 
  given 
  by 
  Berzelius, 
  in 
  his 
  

   Annual 
  Eeport 
  for 
  1847. 
  He 
  makes 
  four 
  different 
  species 
  of 
  feldspar, 
  

   which 
  are 
  easily 
  distinguished 
  from 
  each 
  other 
  : 
  

  

  1. 
  Orthoclase. 
  (feldspar, 
  with 
  a 
  base 
  of 
  potash.) 
  Sp. 
  gr. 
  from 
  2-50 
  

   to 
  2*60. 
  Before 
  the 
  blowpipe 
  it 
  melts 
  with 
  more 
  or 
  less 
  difficulty, 
  and 
  

   yields 
  a 
  bubbly 
  or 
  tuberculous 
  pearl. 
  

  

  2. 
  Albite, 
  (feldspar, 
  with 
  a 
  base 
  of 
  soda,) 
  Sp. 
  gr. 
  2'59 
  to 
  2*65. 
  

   Before 
  the 
  blowpipe 
  it 
  melts 
  more 
  easily 
  than 
  the 
  preceding, 
  and 
  gives 
  a 
  

   bubbly, 
  semitransparent 
  pearl. 
  

  

  3. 
  OUgoclase, 
  (natron 
  spodumen.) 
  Sp. 
  gr. 
  2'61 
  to 
  2*69, 
  and 
  rarely 
  

   2'70. 
  One 
  of 
  the 
  faces 
  of 
  cleavage 
  presents 
  very 
  fine 
  striae. 
  It 
  melts 
  

   easily, 
  and 
  gives 
  a 
  pearl 
  free 
  from 
  bubbles, 
  sometimes 
  transparent, 
  

   sometimes 
  opaline, 
  and 
  sometimes 
  like 
  enamel. 
  These 
  differences 
  

   seem 
  to 
  be 
  due 
  to 
  the 
  proportions 
  of 
  lime 
  which 
  they 
  contain. 
  

  

  None 
  of 
  the 
  three 
  above 
  described, 
  are 
  sensibly 
  acted 
  on 
  by 
  muriatic 
  

   acid. 
  

  

  4. 
  Labradorite. 
  This 
  sometimes 
  presents 
  a 
  striated 
  surface, 
  like 
  the 
  

   preceding. 
  Sp. 
  gr. 
  from 
  2 
  - 
  67 
  to 
  2-73. 
  It 
  melts 
  more 
  easily 
  than 
  oli- 
  

   goclase, 
  and 
  gives 
  rise 
  to 
  a 
  transparent 
  or 
  opaline 
  pearl 
  ; 
  but 
  its 
  most 
  

   distinctive 
  character 
  is 
  its 
  solubility, 
  when 
  pulverized, 
  in 
  muriatic 
  acid. 
  

  

  Mr. 
  Alger, 
  in 
  the 
  supplement 
  to 
  his 
  edition 
  of 
  Phillips' 
  Mineralogy, 
  

   (page 
  420) 
  gives 
  a 
  figure 
  of 
  a 
  twin 
  crystal 
  of 
  feldspar 
  from 
  Hammond. 
  

   St. 
  Lawrence 
  county. 
  It 
  has 
  smooth 
  planes, 
  is 
  very 
  perfect, 
  and 
  is 
  one 
  

   of 
  the 
  simplest 
  of 
  the 
  twin 
  forms. 
  

  

  U 
  .\ 
  

  

  M 
  

  

  T\k 
  

  

  To 
  the 
  locality 
  of 
  crystallized 
  albite, 
  noticed 
  in 
  my 
  Mineralogy, 
  I 
  

   must 
  now 
  add 
  the 
  hemitropic 
  form 
  found 
  by 
  Dr. 
  Emmons 
  in 
  the 
  Coal 
  

   Hill 
  mine, 
  St. 
  Lawrence 
  county. 
  Rep. 
  on 
  the 
  Geol. 
  2d 
  Dist., 
  p. 
  366. 
  

  

  