﻿145 
  

  

  The 
  micas 
  with 
  a 
  single 
  axis, 
  so 
  far 
  as 
  I 
  have 
  examined 
  them, 
  are 
  

   usually 
  more 
  easily 
  fusible 
  than 
  those 
  with 
  a 
  double 
  axis, 
  In 
  thin 
  frag- 
  

   ments 
  they 
  curl 
  up 
  under 
  the 
  blowpipe 
  and 
  fuse 
  into 
  a 
  vermicular 
  en- 
  

   amel, 
  varying 
  in 
  color 
  with 
  the 
  specimen. 
  The 
  following 
  belong 
  to, 
  

  

  HEXAGONAL 
  OR 
  MONOAXIAL 
  MICA. 
  

  

  Forshee's 
  mine, 
  Orange 
  county. 
  Optic 
  axis 
  single; 
  rather 
  difficultly 
  

   fusible. 
  

  

  Copper 
  colored 
  mica, 
  from 
  Edenville, 
  Orange 
  county. 
  Optic 
  axis 
  

   single 
  ; 
  fuses 
  into 
  a 
  dark 
  enamel. 
  

  

  Silvery 
  mica, 
  from 
  Rossie, 
  St. 
  Lawrence. 
  Optic 
  axis 
  single 
  ; 
  fuses 
  

   into 
  a 
  white 
  string. 
  

  

  Mica, 
  from 
  Vrooman 
  lake, 
  Jefferson 
  county. 
  Optic 
  axis 
  single. 
  

  

  Mica, 
  from 
  Gouverneur, 
  St. 
  Lawrence 
  county. 
  Optic 
  axis 
  single. 
  

   In 
  thin 
  plates 
  it 
  fuses 
  into 
  a 
  string 
  of 
  a 
  white 
  color 
  and 
  high 
  lustre. 
  

  

  Copper 
  colored 
  mica, 
  from 
  Edwards, 
  St. 
  Lawrence 
  county. 
  Crys- 
  

   talized 
  in 
  six-sided 
  tables, 
  sometimes 
  5 
  or 
  6 
  inches 
  in 
  diameter; 
  optic 
  

   axis 
  single 
  ; 
  fuses 
  with 
  difficulty 
  into 
  a 
  white 
  mass 
  ; 
  angles 
  of 
  the 
  

   crystals 
  about 
  120° 
  ; 
  lustre 
  metallic 
  ; 
  plates 
  sometimes 
  curved. 
  

  

  Silvery 
  mica, 
  from 
  Edwards. 
  Crystallized 
  in 
  six-sided 
  tables 
  ; 
  optic 
  

   axis 
  single 
  ; 
  fuses 
  rather 
  more 
  easily 
  than 
  the 
  preceding. 
  

  

  The 
  brown 
  mica, 
  from 
  Jefferson 
  county, 
  New- 
  York, 
  has 
  been 
  ana- 
  

   lyzed 
  by 
  Meitzendorff, 
  whose 
  average 
  results 
  are 
  thus 
  stated 
  by 
  Ber- 
  

   zelius, 
  (Arsb. 
  1843, 
  p. 
  211,) 
  silica, 
  41*30; 
  alumina, 
  15-25; 
  peroxide 
  of 
  

   iron, 
  1-77; 
  magnesia, 
  28*79; 
  potash, 
  970 
  ; 
  soda, 
  0*65; 
  fluoric 
  acid, 
  

   3.30 
  ; 
  loss 
  by 
  ignition, 
  0.28. 
  It 
  thus 
  agrees 
  very 
  nearly 
  with 
  Prof. 
  

   H. 
  Rose's 
  analysis 
  of 
  magnesian 
  mica 
  from 
  Siberia. 
  Alger's 
  Phillips, 
  

   619. 
  

  

  ORDER 
  III. 
  GLUCINA. 
  

  

  CHRYSOBERYL. 
  

   (Mineralogy 
  of 
  New- 
  York, 
  page 
  375.) 
  

   To 
  the 
  extensive 
  series 
  of 
  compound 
  crystals 
  figured 
  in 
  the 
  Mineral- 
  

   ogy 
  of 
  New-York, 
  I 
  have 
  to 
  add 
  a 
  few 
  others. 
  For 
  the 
  ability 
  to 
  do 
  

   this, 
  I 
  am 
  indebted 
  to 
  Dr.-Leonard, 
  of 
  Lansingburgh, 
  N. 
  Y., 
  who 
  has 
  

   been 
  uncommonly 
  successful 
  in 
  his 
  exploration 
  of 
  the 
  Greenfield 
  local- 
  

   ity. 
  He 
  has 
  obtained 
  from 
  thence 
  specimens 
  of 
  extraordinary 
  size 
  and 
  

   beauty. 
  Many 
  of 
  them 
  exhibit 
  the 
  forms 
  which 
  I 
  have 
  heretofore 
  

   [Nat. 
  Hist.] 
  10 
  

  

  