﻿ARTICLE 
  V. 
  

  

  On 
  the 
  Crystals 
  developed 
  in 
  Vermiculite 
  by 
  Heat. 
  By 
  Andres 
  Del 
  Rio, 
  

   Professor 
  of 
  Mineralogy 
  in 
  the 
  Mexican 
  School 
  of 
  Mines. 
  Read 
  

   before 
  the 
  American 
  Philosophical 
  Society 
  November 
  1st, 
  1833. 
  

  

  A 
  pupil 
  of 
  the 
  celebrated 
  Werner, 
  I 
  have 
  always 
  been 
  more 
  of 
  a 
  Nep- 
  

   tunian 
  than 
  a 
  Plutonist, 
  notwithstanding 
  the 
  many 
  crystallizations 
  

   produced 
  in 
  the 
  dry 
  way. 
  A 
  new 
  instance 
  which 
  has 
  come 
  under 
  my 
  

   observation 
  in 
  the 
  crystals 
  of 
  vermiculite, 
  has 
  contributed 
  materially 
  to 
  

   change 
  my 
  opinions. 
  

  

  Dr 
  Meigs 
  first 
  showed 
  me 
  the 
  numerous 
  worm-like 
  filaments 
  which 
  

   shoot 
  out 
  from 
  this 
  mineral 
  when 
  held 
  in 
  the 
  flame 
  of 
  a 
  candle 
  : 
  it 
  is 
  

   this 
  property 
  which 
  gives 
  to 
  the 
  mineral 
  its 
  name 
  of 
  vermiculite. 
  

   Under 
  the 
  blow-pipe, 
  and 
  when 
  exposed 
  on 
  a 
  small 
  capsule 
  to 
  the 
  heat 
  

   of 
  a 
  fire, 
  the 
  whole 
  mass 
  started 
  up 
  into 
  numerous 
  oblique 
  rhombic 
  

   prisms, 
  nearly 
  an 
  inch 
  long 
  and 
  more 
  than 
  a 
  line 
  in 
  thickness, 
  crooked 
  

   and 
  wormlike, 
  like 
  the 
  filaments 
  just 
  referred 
  to. 
  These 
  prisms 
  are 
  

   composed 
  of 
  very 
  thin 
  plates 
  of 
  the 
  colour 
  and 
  lustre 
  of 
  silver, 
  placed 
  

   parallel 
  to 
  each 
  other, 
  and 
  oblique 
  to 
  the 
  axes 
  of 
  the 
  prisms. 
  I 
  also 
  

   observed 
  some 
  twin 
  crystals 
  among 
  these 
  groups. 
  

  

  These 
  crystals 
  were 
  digested 
  in 
  sulphuric 
  acid, 
  which 
  separated 
  the 
  

  

  plates 
  from 
  each 
  other, 
  probably 
  by 
  dissolving 
  out 
  portions 
  of 
  the 
  

  

  mineral 
  which 
  were 
  between 
  the 
  plates; 
  these 
  latter 
  remained 
  unat- 
  

  

  tacked 
  by 
  the 
  acid. 
  A 
  partial 
  examination 
  of 
  the 
  solution, 
  made 
  at 
  

  

  vol. 
  v. 
  — 
  2 
  K 
  

  

  