﻿221 
  A. 
  P. 
  lioness 
  — 
  Etching 
  Figures 
  of 
  Beryl. 
  

  

  at 
  Marburg, 
  and 
  the 
  University 
  of 
  Kiel, 
  has 
  prepared 
  a 
  very 
  

   elaborate 
  discussion 
  of 
  natural 
  etch 
  figures. 
  Five 
  forms 
  were 
  

   etched 
  ; 
  the 
  prism 
  is 
  marked 
  by 
  rectangular 
  pits, 
  elongated 
  at 
  

   right 
  angles 
  to 
  the 
  prism 
  edges 
  ; 
  the 
  figures 
  are 
  three 
  mm. 
  long, 
  

   one 
  broad 
  and 
  one-third 
  mm. 
  deep 
  and 
  composed 
  of 
  four 
  tri- 
  

   angular 
  faces 
  meeting 
  in 
  the 
  center 
  of 
  the 
  pit. 
  Smaller 
  figures 
  

   representing 
  other 
  stages 
  of 
  development 
  are 
  also 
  described. 
  

   The 
  second-order 
  prism 
  reveals 
  long, 
  slender, 
  spindle-shaped 
  

   etchings, 
  parallel 
  to 
  the 
  prism 
  edges 
  ; 
  other 
  forms 
  are 
  elongated 
  

   octagons. 
  The 
  first-order 
  pyramid 
  has 
  triangular 
  pits 
  with 
  

   the 
  apex 
  turned 
  downward. 
  Occasionally 
  the 
  apex 
  is 
  truncated 
  

   producing 
  a 
  four-sided 
  figure, 
  symmetrical 
  to 
  a 
  vertical 
  plane. 
  

   The 
  second-order 
  pyramid 
  has 
  many 
  well-defined 
  shield-shaped 
  

   figures, 
  very 
  shallow, 
  with 
  point 
  downward. 
  On 
  the 
  base 
  are 
  

   hexagonal 
  and 
  dihexagonal 
  etchings 
  : 
  some 
  have 
  a 
  base, 
  others 
  

   are 
  pyramidal, 
  but 
  all 
  are 
  symmetrical 
  to 
  six 
  vertical 
  planes. 
  

   Traube* 
  has 
  etched 
  beryl 
  crystals 
  from 
  Elba 
  with 
  potassium 
  

   hydroxide. 
  On 
  the 
  base 
  are 
  regular 
  six-sided 
  forms 
  with 
  the 
  

   edges 
  parallel 
  to 
  0001/1010. 
  On 
  the 
  first-order 
  pyramid 
  are 
  

   triangular 
  figures, 
  apex 
  upward 
  and 
  the 
  longer 
  side 
  parallel 
  to 
  

   1011/1010. 
  The 
  second-order 
  pyramid 
  is 
  marked 
  by 
  four- 
  

   sided 
  pits, 
  with 
  boundaries 
  curved 
  and 
  elongated 
  horizontally. 
  

   Three 
  or 
  four 
  different 
  types 
  of 
  figures 
  are 
  represented 
  on 
  the 
  

   unit 
  prism 
  : 
  some 
  are 
  rectangular 
  with 
  the 
  boundaries 
  straight 
  

   and 
  the 
  long 
  axes 
  parallel 
  to 
  c, 
  others 
  are 
  similarly 
  oriented 
  

   but 
  have 
  curved 
  bounding 
  lines 
  ; 
  still 
  others 
  are 
  quite 
  oval 
  hav- 
  

   ing 
  five 
  faces 
  and 
  elongated 
  parallel 
  to 
  c. 
  All 
  of 
  the 
  figures 
  

   on 
  the 
  various 
  forms 
  indicate 
  the 
  symmetry 
  of 
  the 
  type. 
  With 
  

   potassium 
  fluoride 
  the 
  figures 
  on 
  the 
  base 
  and 
  pyramid 
  faces 
  

   do 
  not 
  differ 
  essentially 
  from 
  the 
  potassium 
  hydroxide 
  figures, 
  

   but 
  the 
  unit 
  prism 
  contains 
  hexagonal 
  forms 
  elongated 
  parallel 
  

   to 
  the 
  prism 
  edges 
  ; 
  other 
  figures 
  appearing 
  on 
  the 
  prism 
  are 
  

   rhombic. 
  The 
  potassium 
  hydroxide 
  etchings 
  of 
  Trail 
  be 
  may 
  

   well 
  be 
  compared 
  and 
  contrasted 
  with 
  the 
  potassium 
  figures 
  of 
  

   the 
  writer 
  as 
  subsequently 
  described 
  and 
  illustrated. 
  

  

  The 
  beryl 
  crystals 
  used 
  for 
  etching 
  were 
  small 
  transparent 
  

   crystals 
  from 
  Elba. 
  They 
  occur 
  in 
  a 
  matrix 
  of 
  feldspar, 
  asso- 
  

   ciated 
  with 
  topaz 
  and 
  tourmaline, 
  very 
  often 
  intimately 
  attached 
  

   to 
  the 
  topaz 
  crystals, 
  which 
  they 
  resemble 
  very 
  closely 
  in 
  form 
  

   and 
  luster. 
  The 
  crystals 
  are 
  not 
  over 
  four 
  or 
  five 
  mm. 
  in 
  

   length 
  and 
  are 
  very 
  simple 
  in 
  form, 
  possessing 
  the 
  unit 
  prism 
  

   1010, 
  the 
  first 
  order 
  pyramid 
  1011, 
  the 
  second 
  order 
  pyramid 
  

   1121, 
  and 
  the 
  base 
  0001. 
  

  

  Various 
  solvents 
  were 
  used 
  for 
  the 
  purpose 
  of 
  etching, 
  but 
  

   the 
  best 
  results 
  were 
  obtained 
  with 
  the 
  alkalie 
  hydroxides 
  

   and 
  a 
  mixture 
  of 
  the 
  same. 
  Hydrofluoric 
  acid, 
  which 
  ordina- 
  

  

  *Traube, 
  Jb. 
  Min. 
  Beil., 
  x, 
  464, 
  1896. 
  

  

  