﻿E. 
  V. 
  Shannon 
  — 
  New 
  Description 
  of 
  Amesite. 
  9 
  S 
  

  

  of 
  1cm. 
  with 
  a 
  thickness 
  of 
  3 
  to 
  5mm. 
  By 
  breaking 
  np 
  

   the 
  diaspore, 
  clean 
  crystals 
  were 
  readily 
  secured 
  and 
  

   these 
  crystals 
  when 
  gronnd 
  were 
  nsed 
  for 
  analysis. 
  The 
  

   material 
  analyzed 
  was 
  perfectly 
  homogeneous 
  and 
  free 
  

   from 
  impurities 
  as 
  shown 
  by 
  optical 
  study. 
  

  

  Physical 
  Properties. 
  — 
  The 
  amesite 
  is 
  of 
  a 
  uniform 
  pale 
  

   bluish 
  green 
  color. 
  The 
  luster 
  is 
  pearly 
  to 
  somewhat 
  

   metallic 
  on 
  cleavage 
  surfaces. 
  In 
  thick 
  pieces 
  the 
  min- 
  

   eral 
  is 
  translucent 
  to 
  almost 
  opaque. 
  Thin 
  fragments 
  

   are 
  transparent. 
  The 
  powder 
  is 
  white 
  with 
  a 
  very 
  faint 
  

   tinge 
  of 
  green. 
  The 
  mineral 
  has 
  a 
  micaceous 
  basal 
  

   cleavage 
  which, 
  however, 
  is 
  not 
  nearly 
  so 
  perfect 
  as 
  in 
  

   most 
  crystallized 
  chlorites. 
  Laminae 
  are 
  rather 
  brittle 
  

   and 
  break 
  in 
  a 
  manner 
  suggesting 
  a 
  very 
  imperfect 
  pris- 
  

   matic 
  cleavage. 
  The 
  hardness 
  is 
  about 
  2-3 
  as 
  it 
  scratches 
  

   gypsum 
  readily 
  but 
  is 
  scratched 
  with 
  great 
  ease 
  by 
  cal- 
  

   cite. 
  The 
  specific 
  gravity 
  as 
  determined 
  on 
  approxi- 
  

   mately 
  3 
  grams 
  of 
  coarse 
  fragments 
  in 
  a 
  pygnometer 
  is 
  

   2-77. 
  

  

  Optical 
  Properties. 
  — 
  Cleavage 
  plates 
  of 
  the 
  amesite 
  

   are 
  dark 
  in 
  all 
  positions 
  between 
  crossed 
  nicols. 
  Ex- 
  

   amined 
  in 
  convergent 
  light 
  a 
  black 
  cross 
  is 
  obtained 
  

   which 
  separates 
  slightly 
  on 
  rotation 
  of 
  the 
  stage 
  indicat- 
  

   ing 
  that 
  the 
  mineral 
  is 
  biaxial 
  with 
  the 
  axial 
  angle, 
  2V, 
  

   very 
  small, 
  acute 
  bisectrix 
  normal 
  to 
  the 
  perfect 
  cleav- 
  

   age. 
  The 
  optical 
  character 
  is 
  positive. 
  The 
  mineral 
  is 
  

   colorless 
  as 
  seen 
  under 
  the 
  microscope. 
  The 
  refractive 
  

   indices 
  measured 
  by 
  the 
  immersion 
  method 
  were 
  found 
  

   to 
  be 
  as 
  follows 
  : 
  4 
  

  

  a 
  = 
  1-597 
  ± 
  -003 
  

   £ 
  = 
  1-597 
  ± 
  -003 
  

   y 
  = 
  1-612 
  ± 
  003 
  

  

  a-y 
  = 
  -010 
  ± 
  -003 
  

  

  Chemical 
  Properties. 
  — 
  Heated 
  before 
  the 
  blowpipe 
  the 
  

   amesite 
  swells 
  somewhat 
  and 
  exfoliates 
  slightly 
  becom- 
  

   ing 
  silvery 
  brownish 
  white 
  in 
  color. 
  It 
  is 
  infusible. 
  It 
  

   does 
  not 
  become 
  magnetic 
  when 
  roasted 
  on 
  charcoal. 
  It 
  

   yields 
  considerable 
  water 
  in 
  the 
  closed 
  tube. 
  The 
  main 
  

   portion 
  of 
  the 
  water 
  is 
  basic 
  coming 
  off 
  only 
  at 
  a 
  dull 
  red 
  

   heat. 
  The 
  mineral 
  is 
  partially 
  decomposed 
  by 
  boiling 
  in 
  

   sulphuric, 
  nitric 
  or 
  hydrochloric 
  acid 
  with 
  separation 
  of 
  

   flocculent 
  silica. 
  Upon 
  analysis 
  the 
  pure 
  powder 
  yields 
  

   the 
  following 
  results 
  : 
  

  

  4 
  Values 
  confirmed 
  "by 
  E. 
  S. 
  Larsen. 
  

  

  