﻿268 
  THE 
  EAUENTHAL 
  SERPENTINE. 
  [May 
  1 
  89 
  7, 
  

  

  Plate 
  XVII. 
  

   All 
  the 
  figures 
  are 
  X 
  20. 
  Figs. 
  2-6 
  are 
  of 
  Eauenthal 
  serpentine. 
  

  

  Fig. 
  1. 
  A 
  slice 
  from 
  the 
  Bonhomme 
  serpentine 
  (which 
  is 
  admitted 
  to 
  be 
  an 
  

   olivine-serpentine), 
  to 
  illustrate 
  the 
  similarity 
  to 
  the 
  Eauenthal 
  rock. 
  

   The 
  drawing 
  shows 
  accessory 
  hornblende-crystals, 
  serpentinized, 
  

   among 
  olivine-serpentine 
  as 
  in 
  fig. 
  2 
  from 
  the 
  Eauenthal. 
  The 
  chief 
  

   differences 
  are, 
  in 
  the 
  Bonhomme 
  rock, 
  the 
  presence 
  of 
  picotite 
  

   (represented 
  together 
  with 
  opacite 
  by 
  dark 
  spots 
  in 
  the 
  drawing) 
  and 
  

   the 
  occurrence 
  of 
  some 
  residual 
  unchanged 
  olivine. 
  

  

  Fig. 
  2. 
  Crystals 
  of 
  accessory 
  hornblende, 
  serpentinized, 
  but 
  still 
  exhibiting 
  

   characteristic 
  cleavage, 
  within 
  a 
  mass 
  of 
  olivine-serpentine. 
  Iron 
  

   oxide, 
  with 
  amount 
  and 
  arrangement 
  as 
  usual, 
  occurs 
  in 
  the 
  slide. 
  

   Serpentinized 
  enstatite 
  and 
  chlorite 
  are 
  also 
  present, 
  but 
  are 
  not 
  

   shown 
  in 
  the 
  drawing. 
  (The 
  darker 
  tint 
  of 
  this 
  figure, 
  as 
  compared 
  

   with 
  fig. 
  1, 
  is 
  due 
  to 
  the 
  slice 
  of 
  the 
  rock 
  being 
  much 
  thicker.) 
  

  

  Fig 
  3. 
  Chlorite 
  accompanying 
  and 
  enclosed 
  within 
  olivine-serpentine, 
  associated 
  

   with 
  partly-changed 
  hornblende. 
  Some 
  of 
  the 
  chlorite 
  is 
  in 
  a 
  tran- 
  

   sitional 
  condition, 
  evidently 
  forming 
  from 
  mica. 
  Crystalline 
  grains 
  

   of 
  iron 
  oxide 
  are 
  present. 
  

  

  Fig 
  4. 
  ' 
  Amphibolite 
  ' 
  consisting 
  of 
  hornblende, 
  mostly 
  unaltered, 
  sometimes 
  

   in 
  idiomorphic 
  crystals, 
  associated 
  with 
  well-developed 
  chlorite. 
  

   (Band 
  in 
  Eauenthal 
  serpentine.) 
  

  

  Fig. 
  5. 
  Interstreaking 
  of 
  greenish 
  olivine-serpentine 
  and 
  colourless 
  well-cleaved 
  

   hornblende 
  ('amphibolite'). 
  Iron 
  oxide 
  is 
  present. 
  Structure 
  

   probably 
  fluxional. 
  

  

  Fig. 
  6. 
  Olivine-serpentine, 
  with 
  the 
  usual 
  mesh 
  work- 
  structure. 
  Many 
  of 
  the 
  

   fine 
  dots 
  over 
  the 
  grains 
  represent 
  minute 
  granules 
  of 
  ferrite, 
  probably 
  

   haematite 
  ; 
  and 
  a 
  few 
  larger 
  patches 
  of 
  opacite 
  and 
  ferrite 
  are 
  shown 
  

   in 
  the 
  drawing. 
  Chlorite 
  occurs 
  in 
  parallel 
  or 
  orientated 
  flakes, 
  but 
  

   no 
  hornblende 
  is 
  associated 
  with 
  it. 
  

  

  Discussion. 
  

  

  Prof. 
  Judd 
  called 
  attention 
  to 
  the 
  fact 
  that 
  the 
  relations 
  of 
  the 
  

   serpentine 
  of 
  the 
  Rauenthal 
  to 
  the 
  adjacent 
  granites 
  and 
  gneisses, 
  

   as 
  described 
  by 
  the 
  Author 
  of 
  the 
  paper, 
  are 
  strikingly 
  like 
  those 
  of 
  

   the 
  peridotites 
  and 
  serpentines 
  of 
  North 
  Carolina 
  and 
  Georgia 
  to 
  the 
  

   granites 
  and 
  gneisses 
  of 
  that 
  area. 
  

  

  Mr. 
  Kutley 
  said 
  that 
  the 
  rocks 
  included 
  within 
  the 
  area 
  described 
  

   would 
  unquestionably 
  yield 
  serpentines 
  varying 
  considerably 
  in 
  

   character. 
  One 
  of 
  these 
  rocks 
  was 
  stated 
  to 
  be 
  amphibolite, 
  and, 
  

   although 
  the 
  nature 
  of 
  rocks 
  bearing 
  this 
  name 
  is 
  open 
  to 
  question, 
  

   he 
  thought 
  that 
  in 
  certain 
  cases 
  amphibolites 
  were 
  eruptive 
  rocks. 
  

   When 
  the 
  hornblende 
  of 
  an 
  amphibolite 
  was 
  converted 
  into 
  ser- 
  

   pentine, 
  it 
  would 
  be 
  interesting 
  to 
  know 
  what 
  became 
  of 
  the 
  other 
  

   constituents. 
  He 
  appreciated 
  the 
  straightforward 
  way 
  in 
  which 
  

   only 
  actual 
  exposures 
  were 
  represented 
  on 
  the 
  map, 
  and 
  believed 
  

   that 
  the 
  paper, 
  when 
  printed 
  in 
  full, 
  would 
  be 
  a 
  valuable 
  addition 
  

   to 
  the 
  literature 
  relating 
  to 
  serpentines 
  and 
  their 
  origin. 
  

  

  Prof. 
  Bonnet 
  stated 
  that 
  the 
  mode 
  in 
  which 
  the 
  serpentine 
  

   occurred 
  corresponded 
  with 
  what 
  could 
  be 
  seen 
  in 
  several 
  localities. 
  

   The 
  question 
  of 
  the 
  connexion 
  of 
  the 
  foliation 
  of 
  the 
  serpentine 
  

   with 
  pressure 
  had 
  always 
  been 
  present 
  to 
  the 
  mind 
  of 
  the 
  Authoress, 
  

   but 
  no 
  connexion 
  had 
  been 
  proved. 
  He 
  agreed 
  with 
  Mr. 
  Rutley 
  

   that 
  amphibolite 
  was 
  generally 
  an 
  igneous 
  rock. 
  There 
  was 
  a 
  

   difficulty 
  in 
  accounting 
  for 
  the 
  missing 
  silica 
  ; 
  but 
  the 
  fact 
  of 
  the 
  

   change 
  of 
  certain 
  pyroxenes 
  into 
  serpentine 
  was 
  indubitable. 
  This 
  

   rock, 
  however, 
  had 
  originated 
  from 
  a 
  peridotite. 
  

  

  