﻿REPORT 
  OF 
  THE 
  DIRECTOR 
  37 
  

  

  Prof. 
  Volger 
  from 
  his 
  examination 
  of 
  this 
  material 
  arrived 
  at 
  a 
  sim- 
  

   ilar 
  conclusion. 
  

  

  Since 
  the 
  development 
  of 
  microscopic 
  methods 
  of 
  research 
  a 
  

   large 
  number 
  of 
  eminent 
  investigators 
  have 
  studied 
  the 
  structure 
  and 
  

   optical 
  properties 
  of 
  serpentine, 
  and 
  all, 
  including 
  Tschermak, 
  Ros- 
  

   enbusch, 
  Kalowsky, 
  Websky, 
  Wiik, 
  Des 
  Cloizeaux, 
  Von 
  Drasche 
  

   and 
  Fischer, 
  are 
  unanimous 
  in 
  considering 
  it 
  an 
  alteration 
  product 
  of 
  

   anhydrous 
  magnesian 
  silicates. 
  Prof. 
  Rosenbusch 
  in 
  his 
  late 
  v/ork 
  

   on 
  rock-making 
  minerals.* 
  Epitomizes 
  the 
  latest 
  knowledge 
  of 
  the 
  

   subject 
  as 
  follows: 
  — 
  

  

  " 
  Serpentine, 
  according 
  to 
  the 
  mineral 
  from 
  which 
  it 
  is 
  derived, 
  

   has 
  a 
  fibrous 
  or 
  apparently 
  lamellar 
  structure. 
  The 
  apparent 
  lamellae 
  

   may, 
  however, 
  only 
  represent 
  parallel 
  bundles 
  of 
  fibres. 
  The 
  ar- 
  

   rangement 
  of 
  the 
  fibres 
  is 
  quite 
  varied. 
  They 
  are 
  sometimes 
  parallel 
  

   and 
  sometimes 
  confusedly 
  felted 
  and 
  the 
  optical 
  characters 
  of 
  the 
  

   fibres 
  between 
  crossed 
  nicols 
  change 
  with 
  their 
  dimensions 
  and 
  their 
  

   arrangement. 
  In 
  parallel 
  aggregates, 
  which 
  are 
  not 
  too 
  finely 
  

   fibrous, 
  one 
  may 
  recognize 
  with 
  certainty 
  that 
  they 
  are 
  biaxial 
  with 
  

   very 
  large 
  axial 
  angles 
  the 
  negative 
  bisectrix 
  of 
  which 
  is 
  perpendicu- 
  

   lar 
  to 
  the 
  axis 
  of 
  the 
  fibre 
  which 
  is 
  the 
  axis 
  of 
  least 
  elasticity. 
  These 
  

   fibres 
  have 
  a 
  weak 
  refractive 
  power 
  (very 
  near 
  that 
  of 
  Canada 
  balsam) 
  

   and 
  not 
  inconsiderable 
  double 
  refraction. 
  Chrysotile 
  exhibits 
  these 
  

   properties 
  very 
  clearly. 
  In 
  the 
  finely 
  and 
  confusedly 
  fibrous 
  aggre- 
  

   gates 
  very 
  nearly 
  complete 
  compensation 
  occurs 
  so 
  that 
  these 
  often 
  

   appear 
  to 
  be 
  isotropic. 
  

  

  *' 
  The 
  mineral 
  from 
  which 
  serpentine 
  is 
  most 
  frequently 
  derived 
  is 
  

   olivine. 
  The 
  alteration 
  begins 
  from 
  the 
  surface 
  and 
  from 
  the 
  crevices 
  

   and 
  leads 
  to 
  a 
  fibrous 
  structure 
  with 
  simultaneous 
  separation 
  of 
  the 
  

   iron 
  content 
  in 
  the 
  form 
  of 
  Fe203, 
  2Fe203, 
  + 
  3H2O 
  and 
  Fe304. 
  

   The 
  new 
  structures 
  of 
  greenish 
  to 
  yellowish-green 
  color 
  are 
  perpen- 
  

   dicular 
  to 
  the 
  crystal 
  boundaries 
  and 
  the 
  cracks. 
  Since 
  the 
  alteration 
  

   takes 
  place 
  from 
  all 
  the 
  cracks 
  (which 
  cross 
  each 
  other 
  confusedly) 
  

   , 
  and 
  from 
  the 
  sides 
  simultaneously, 
  an 
  olivine 
  in 
  which 
  the 
  alteration 
  

   into 
  serpentine 
  has 
  begun, 
  appears 
  to 
  have 
  a 
  reticulate 
  structure. 
  The 
  

   serpentine 
  strings 
  form 
  a 
  network 
  of 
  which 
  the 
  meshes 
  inclose 
  olivine 
  

  

  * 
  Mik. 
  Phys. 
  der 
  Pet. 
  Wicht. 
  Miner. 
  2te 
  Aufl. 
  pp. 
  557-559 
  

  

  