﻿Vol* 
  53«] 
  ORIGIN 
  OF 
  THE 
  RATJENTHAL 
  SERPENTINE. 
  249 
  

  

  surface. 
  In 
  the 
  serpentine, 
  enstatite-crystals 
  are 
  sometimes 
  seen 
  

   on 
  the 
  cross-fractnre 
  planes, 
  where 
  the 
  chlorite 
  is 
  not 
  visible. 
  This 
  

   platy 
  serpentine 
  rich 
  in 
  chlorite 
  can 
  be 
  recognized 
  in 
  many 
  crags 
  

   (see 
  PI. 
  XVI). 
  In 
  a 
  second 
  form 
  of 
  the 
  rock 
  the 
  chlorite-flakes 
  

   are 
  much 
  smaller, 
  more 
  crowded, 
  and 
  not 
  orientated. 
  A 
  third 
  

   variety 
  is 
  massive, 
  dark 
  rich 
  greenish, 
  not 
  platy, 
  without 
  chlorite, 
  

   but 
  containing 
  well-developed 
  enstatite 
  or 
  bronzite. 
  Fourthly, 
  the 
  

   serpentine 
  may 
  be 
  mottled 
  with 
  greenish 
  patches, 
  or 
  a 
  similar 
  

   material 
  may 
  form 
  streaks 
  and 
  laminse 
  sometimes 
  about 
  J 
  inch 
  

   thick 
  ; 
  these 
  patches 
  and 
  layers 
  are 
  somewhat 
  indefinite 
  in 
  outline. 
  

   Lastly, 
  the 
  peculiar 
  amphibolite 
  occurs 
  in 
  places. 
  Where 
  typi- 
  

   cally 
  developed 
  it 
  is 
  a 
  beautiful 
  mass 
  of 
  glittering, 
  silvery, 
  pale- 
  

   greenish 
  crystal-fiakes, 
  orientated 
  so 
  as 
  to 
  produce 
  an 
  appearance 
  of 
  

   foliation. 
  Examples 
  of 
  it 
  are 
  found 
  in 
  at 
  least 
  five 
  of 
  the 
  serpentine- 
  

   crags. 
  It 
  often 
  forms 
  layers 
  an 
  inch 
  or 
  two 
  in 
  thickness 
  embedded 
  

   in 
  normal 
  serpentine, 
  and 
  the 
  two 
  rocks 
  are 
  clearly 
  distinguishable 
  

   in 
  the 
  crags, 
  although 
  the 
  boundary 
  is 
  not 
  always 
  sharply 
  defined, 
  

   a 
  certain 
  indentation 
  or 
  mixiDg 
  being 
  visible 
  on 
  close 
  examination. 
  

  

  Olivine-serpentine 
  and 
  ' 
  aniphibolite 
  ' 
  (Bauenthal) 
  in 
  thin 
  section. 
  

  

  The 
  darker-spotted 
  parts 
  represent 
  the 
  distinctly 
  green 
  portions 
  of 
  the 
  slice, 
  

   which 
  are 
  composed 
  of 
  olivine-serpentine. 
  The 
  paler 
  areas 
  represent 
  the 
  

   ' 
  amphibolite,' 
  which 
  is 
  colourless. 
  ( 
  X 
  2^.) 
  

  

  Thus 
  the 
  amphibolite-bands 
  occur 
  not 
  along 
  the 
  limit 
  of 
  the 
  ser- 
  

   pentine, 
  but 
  included 
  in 
  it 
  (see 
  PI. 
  XVI). 
  Again, 
  the 
  loose 
  blocks 
  

   in 
  the 
  valley 
  show 
  the 
  amphibolite 
  and 
  serpentine 
  in 
  similar 
  relations. 
  

   Another 
  mode 
  of 
  association, 
  however, 
  is 
  exhibited 
  in 
  certain 
  

   loose 
  boulders, 
  and 
  in 
  one 
  crag 
  near 
  to 
  and 
  south 
  of 
  the 
  streamlet. 
  

   Q. 
  J. 
  G. 
  S. 
  No. 
  210. 
  s 
  

  

  