﻿A. 
  P. 
  lioness 
  — 
  Etching 
  Figures 
  of 
  Beryl. 
  

  

  233 
  

  

  diagram 
  F, 
  fig. 
  15) 
  ; 
  some 
  are 
  terminated 
  by 
  a 
  basal 
  plane, 
  

   others 
  are 
  pyramidal 
  with 
  the 
  six 
  bounding 
  planes 
  lying 
  

   approximately 
  in 
  the 
  plane 
  of 
  the 
  first-order 
  pyramid 
  ; 
  both 
  

   forms 
  are 
  symmetrical 
  to 
  six 
  vertical 
  planes, 
  which 
  conforms 
  

   to 
  the 
  symmetry 
  of 
  the 
  type. 
  

  

  Another 
  form 
  of 
  natural 
  etch 
  figure 
  occurs 
  on 
  a 
  beautiful 
  

   emerald 
  from 
  Musa 
  Valley, 
  near 
  Bogota, 
  United 
  States 
  of 
  

   Columbia 
  (diagram 
  B, 
  fig. 
  13). 
  Three 
  forms 
  are 
  etched. 
  

  

  Fig. 
  15. 
  

  

  DiaG 
  

  

  DiaF 
  

  

  Prism. 
  — 
  The 
  unit 
  prism 
  1010 
  is 
  beautifully 
  pitted 
  with 
  

   quadrilateral 
  figures, 
  many 
  of 
  them 
  being 
  perfect 
  squares 
  with 
  

   four 
  sloping 
  planes 
  ; 
  others 
  are 
  slightly 
  elongated 
  at 
  right 
  

   angles 
  to 
  the 
  vertical 
  axis 
  of 
  the 
  crystal, 
  but 
  all 
  angles 
  are 
  

   ninety 
  degrees, 
  as 
  in 
  the 
  more 
  regular 
  type. 
  The 
  right 
  and 
  

   left 
  faces 
  of 
  the 
  figures 
  lie 
  in 
  the 
  prism 
  zone, 
  the 
  upper 
  and 
  

   lower 
  faces 
  lie 
  in 
  the 
  zone 
  of 
  the 
  first 
  : 
  order 
  pyramid 
  and 
  the 
  

   base. 
  The 
  position 
  as 
  regards 
  the 
  intercept 
  could 
  not 
  be 
  

   accurately 
  determined 
  as 
  these 
  pits 
  would 
  not 
  yield 
  casts 
  of 
  

   sufficient 
  size 
  for 
  measurement. 
  The 
  figures 
  are 
  very 
  inter- 
  

   esting 
  from 
  a 
  genetic 
  point 
  of 
  view, 
  as 
  they 
  are 
  identical 
  in 
  

   form 
  with 
  the 
  artificial 
  figures 
  produced 
  by 
  the 
  writer 
  on 
  the 
  

   unit 
  prism 
  of 
  a 
  North 
  Carolina 
  beryl, 
  by 
  sodium 
  hydroxide 
  ; 
  

   they 
  are 
  perfect 
  duplications 
  at 
  this 
  state 
  of 
  growth. 
  This 
  is 
  

   to 
  be 
  noted, 
  however: 
  if 
  the 
  artificial 
  figures 
  are 
  allowed 
  to 
  

   develop 
  to 
  a 
  more 
  mature 
  stage, 
  they 
  assume 
  an 
  elongated 
  ap- 
  

   pearance 
  exactly 
  as 
  do 
  the 
  natural 
  etchings 
  on 
  the 
  emerald 
  

   from 
  Musa 
  Valley, 
  South 
  America, 
  but 
  they 
  differ 
  in 
  orienta- 
  

   tion 
  ; 
  the 
  former 
  have 
  their 
  long 
  axes 
  parallel 
  to 
  c\ 
  the 
  latter 
  

  

  