﻿Vol. 
  53.] 
  ORIGIN 
  OP 
  THE 
  RAUENTHAL 
  SERPENTINE. 
  255 
  

  

  intervening 
  bands, 
  as 
  indicated 
  by 
  Prof. 
  Bonney. 
  1 
  Thus, 
  even 
  apart 
  

   from 
  the 
  chlorite, 
  iron 
  oxide 
  is 
  not 
  entirely 
  absent 
  2 
  ; 
  but 
  it 
  is 
  true 
  

   that 
  the 
  strongly 
  marked 
  black 
  or 
  brownish 
  network 
  of 
  many 
  

   serpentines 
  is 
  not 
  here 
  visible. 
  

  

  I 
  fail 
  to 
  see, 
  however, 
  that 
  this 
  fact 
  leads 
  to 
  any 
  other 
  inference 
  

   than 
  that 
  the 
  original 
  olivine 
  was 
  not 
  a 
  ferriferous 
  variety. 
  It 
  

   would 
  seem 
  that 
  the 
  original 
  magma 
  was 
  one 
  rather 
  poor 
  in 
  iron, 
  

   for 
  the 
  colourless 
  hornblende 
  probably 
  owes 
  its 
  peculiarity 
  to 
  a 
  want 
  

   of 
  the 
  ferruginous 
  constituent. 
  3 
  Much 
  of 
  the 
  iron 
  oxide 
  which 
  is 
  

   present 
  in 
  the 
  serpentine 
  seems 
  to 
  be 
  associated 
  with 
  the 
  peculiar 
  

   chlorite. 
  In 
  certain 
  specimens, 
  however, 
  the 
  olivine-serpentine 
  is 
  

   more 
  ferruginous, 
  with 
  grains 
  of 
  magnetite 
  (?) 
  and 
  so 
  much 
  scattered 
  

   minute 
  opacite 
  that 
  it 
  gives 
  a 
  bluish 
  tinge 
  to 
  parts 
  of 
  the 
  slide 
  : 
  but 
  

   here 
  no 
  chlorite 
  is 
  exhibited. 
  

  

  (3) 
  Microscopic 
  Structure 
  of 
  the 
  Serpentine. 
  

  

  (1) 
  After 
  the 
  accurate 
  description 
  of 
  the 
  serpentinization 
  of 
  

   hornblende, 
  Herr 
  Weigand 
  goes 
  on 
  to 
  state 
  that 
  ' 
  the 
  same 
  arrange- 
  

   ment 
  is 
  found 
  everywhere 
  in 
  the 
  serpentine,' 
  4 
  and 
  that 
  it 
  ' 
  follows 
  

   without 
  doubt 
  that 
  .... 
  a 
  serpentine 
  .... 
  in 
  great 
  masses 
  .... 
  has 
  

   originated 
  from 
  amphibolite.' 
  5 
  It 
  was 
  shown 
  by 
  Prof. 
  Bonney 
  that 
  

   the 
  serpentine 
  had 
  not 
  so 
  universal 
  and 
  uniform 
  a 
  character, 
  and 
  

   that 
  the 
  major 
  part 
  of 
  it 
  can 
  be 
  distinguished 
  from 
  the 
  serpentinized 
  

   crystals 
  of 
  hornblende. 
  6 
  We 
  cannot 
  ignore 
  the 
  differences 
  which 
  

   certainly 
  exist, 
  which 
  Weigand 
  himself 
  to 
  a 
  certain 
  extent 
  recognizes 
  

   from 
  his 
  words 
  the 
  ' 
  larger 
  rounded 
  parts.' 
  ~ 
  This 
  phrase 
  alone 
  

   suggests 
  two 
  differences 
  ; 
  others 
  have 
  now 
  been 
  added 
  ; 
  and 
  the 
  

   true 
  explanation 
  seems 
  to 
  be 
  that 
  the 
  part 
  with 
  ' 
  larger 
  rounded 
  ' 
  

   kernels 
  is 
  the 
  result 
  of 
  the 
  serpentinization 
  of 
  an 
  oli 
  vine-mass 
  

   (PL 
  XVII. 
  figs. 
  2, 
  6). 
  In 
  fact 
  the 
  hornblende 
  occurs 
  as 
  an 
  accessory 
  

   in 
  an 
  original 
  peridotite, 
  just 
  as 
  that 
  mineral 
  is 
  found 
  in 
  parts 
  of 
  

   the 
  Lizard 
  serpentine. 
  

  

  (2) 
  We 
  are 
  told 
  that 
  this 
  Rauenthal 
  serpentine 
  does 
  not 
  exhibit 
  

   the 
  ' 
  irregular 
  network 
  ' 
  which 
  is 
  characteristic 
  of 
  olivine-serpen 
  - 
  

   tines. 
  8 
  Here 
  there 
  is 
  a 
  network 
  — 
  it 
  is 
  only 
  therefore 
  a 
  question 
  of 
  

  

  1 
  Geol. 
  Mag. 
  1887, 
  p. 
  68. 
  

  

  2 
  Indeed 
  this 
  appears 
  to 
  be 
  acknowledged, 
  although 
  the 
  statements 
  do 
  not 
  

   seem 
  perfectly 
  clear 
  : 
  — 
  'Die 
  Analyse 
  zeigt 
  also 
  in 
  Uebereinstimmung 
  mit 
  der 
  

   mikroskopischen 
  TTntersuchung 
  eine 
  grosse 
  Menge 
  Eisen.' 
  (B. 
  Weigand, 
  op. 
  

   dtp. 
  200.) 
  

  

  3 
  The 
  analysis 
  of 
  the 
  amphibolite 
  given 
  by 
  Weigand 
  includes 
  Fe 
  2 
  3 
  4*649, 
  

   FeO 
  2-107, 
  but 
  the 
  analysis 
  was 
  obtained, 
  we 
  are 
  told, 
  from 
  material 
  which 
  

   included 
  some 
  serpentine. 
  

  

  4 
  ' 
  Zeigt 
  sich 
  dieselbe 
  gitter- 
  und 
  fensterformige 
  Structur 
  iiber 
  das 
  ganze 
  

   G-esichtsfeld 
  verbreitet 
  ' 
  (op. 
  tit. 
  p. 
  198) 
  ; 
  ' 
  . 
  . 
  . 
  . 
  man 
  im 
  Serpentine 
  selbst 
  

   inittelst 
  des 
  polarisirten 
  Lichtes 
  den 
  Chrysot.il 
  in 
  derselben 
  AnordnuDg 
  iiberall 
  

   wiederfindet 
  wie 
  in 
  der 
  Hornblende 
  . 
  . 
  .' 
  (op. 
  tit. 
  p. 
  200). 
  

  

  5 
  ' 
  Geht 
  unzweifelhaft 
  hervor, 
  dass 
  .... 
  wir 
  also 
  hier 
  einen 
  in 
  grossen 
  

   Massen 
  auftretenden 
  Serpentin 
  haben, 
  der 
  aus 
  Amphibolit 
  entstanden 
  ist 
  ' 
  

   (op. 
  tit. 
  pp. 
  200-201). 
  6 
  Geol. 
  Mag. 
  1887, 
  p. 
  68. 
  

  

  7 
  Op. 
  tit. 
  p. 
  197 
  : 
  ' 
  grossere 
  rundliche 
  Partien.' 
  

   s 
  B. 
  Weigand, 
  op. 
  tit. 
  p. 
  201. 
  

  

  