﻿262 
  MISS 
  C. 
  A. 
  RAISIN 
  ON 
  THE 
  NATURE 
  AND 
  [May 
  1 
  897, 
  

  

  having 
  the 
  meshwork-structure 
  of 
  a 
  mass 
  developed 
  from 
  olivine, 
  

   and, 
  except 
  in 
  the 
  presence 
  of 
  rather 
  more 
  magnetite 
  than 
  occurs 
  

   in 
  most 
  but 
  not 
  in 
  all 
  of 
  the 
  Rauenthal 
  rock, 
  this 
  has 
  a 
  similarity, 
  

   we 
  might 
  say 
  an 
  identity, 
  with 
  the 
  parts 
  of 
  that 
  serpentine 
  which 
  

   may 
  be 
  claimed 
  as 
  showing 
  an 
  olivine 
  structure. 
  In 
  many 
  kernels 
  

   of 
  the 
  original 
  mineral 
  a 
  border 
  occurs, 
  of 
  slender 
  ru 
  tile-rods 
  with 
  

   a 
  radial 
  arrangement 
  as 
  I 
  have 
  described 
  it 
  above 
  in 
  a 
  Rauenthal 
  

   serpentine 
  (p. 
  253). 
  In 
  another 
  slice 
  from 
  Starkenbach 
  we 
  can 
  

   trace 
  all 
  stages 
  in 
  the 
  alteration. 
  In 
  the 
  completely 
  altered 
  rock, 
  

   strings 
  of 
  serpentine, 
  often 
  straight, 
  not 
  seldom 
  form 
  a 
  rudely 
  

   rectangular 
  network 
  or 
  even 
  occasionally 
  cross 
  at 
  angles 
  of 
  nearly 
  

   120°. 
  In 
  other 
  words, 
  it 
  has 
  the 
  characters 
  of 
  most 
  of 
  the 
  Eauenthal 
  

   serpentine, 
  but 
  here 
  is 
  associated 
  with 
  distinct 
  remains 
  of 
  olivine. 
  

   Serpentinized 
  enstatite 
  and 
  picotite 
  occur, 
  as 
  described 
  ; 
  a 
  colourless 
  

   hornblende 
  and 
  a 
  white 
  augite 
  are 
  also 
  present. 
  

  

  (ii) 
  The 
  strongest 
  resemblance, 
  however, 
  can 
  be 
  found 
  in 
  parts 
  

   of 
  the 
  mass 
  which 
  is 
  claimed 
  by 
  Herr 
  Weigand 
  as 
  an 
  olivine-serpen- 
  

   tine 
  — 
  that 
  at 
  JBonhomme. 
  This 
  rock 
  shows 
  much 
  variation, 
  includes 
  

   sometimes 
  the 
  patches 
  described 
  as 
  modified 
  garnets, 
  1 
  sometimes 
  

   picotite 
  in 
  exceptional 
  abundance, 
  sometimes 
  serpentinized 
  enstatite 
  

   or 
  clustered 
  augite 
  or 
  hornblende. 
  Most 
  of 
  the 
  serpentine 
  has 
  been 
  

   derived 
  from 
  olivine, 
  but 
  at 
  parts 
  well-cleaved 
  crystals 
  of 
  hornblende 
  

   more 
  or 
  less 
  serpentinized 
  occur, 
  which, 
  like 
  the 
  chlorite 
  or 
  the 
  

   hornblende 
  within 
  the 
  Hauenthal 
  rock, 
  are 
  ' 
  grouped 
  in 
  layers 
  ' 
  or 
  

   ' 
  scattered 
  quite 
  irregularly.' 
  One 
  slice 
  which 
  consists 
  mainly 
  of 
  

   olivine 
  (some 
  kernels 
  still 
  remaining 
  unchanged), 
  but 
  includes 
  

   several 
  crystals 
  of 
  partially 
  altered 
  hornblende, 
  seems 
  to 
  give 
  a 
  

   perfect 
  representation 
  of 
  what 
  parts 
  of 
  the 
  Hauenthal 
  rock 
  should 
  

   have 
  been 
  at 
  an 
  earlier 
  stage 
  (PI. 
  XVII. 
  fig. 
  1). 
  

  

  This 
  mass 
  it 
  was 
  which 
  first 
  furnished 
  evidence, 
  conclusive 
  in 
  

   my 
  opinion, 
  of 
  the 
  origin 
  of 
  the 
  peculiar 
  chlorite 
  already 
  discussed. 
  

   Glittering 
  silvery 
  flakes 
  occur 
  on 
  certain 
  specimens, 
  2 
  and 
  microscopic 
  

   investigation 
  proved 
  their 
  identity 
  with 
  the 
  chlorite 
  ; 
  but 
  in 
  the 
  

   same 
  slide 
  the 
  mineral 
  could 
  be 
  traced 
  associated 
  with, 
  and 
  evidently 
  

   developed 
  from, 
  a 
  variety 
  of 
  mica. 
  This 
  is 
  pale 
  brownish, 
  with 
  

   pleochroism 
  from 
  almost 
  colourless 
  to 
  that 
  tint, 
  and 
  resembles 
  the 
  

   form 
  of 
  phlogopite 
  seen 
  in 
  the 
  Kimberley 
  peridotite. 
  3 
  A 
  specimen 
  

   from 
  among 
  tumbled 
  blocks, 
  which 
  are 
  almost 
  in 
  situ 
  by 
  the 
  road 
  

   just 
  south 
  of 
  the 
  col, 
  has 
  mica 
  occurring 
  in 
  larger 
  flakes, 
  also 
  large 
  

   enstatite- 
  crystals, 
  and 
  a 
  bright 
  green 
  apparently 
  chloritic 
  mineral. 
  

   The 
  specimen 
  is 
  practically 
  identical 
  with 
  a 
  rock 
  from 
  Portsoy. 
  4 
  

  

  1 
  B. 
  Weigand, 
  op. 
  cit. 
  p. 
  190. 
  The 
  interesting 
  structure 
  of 
  these 
  must 
  be 
  

   left 
  for 
  future 
  investigation, 
  since 
  it 
  has 
  no 
  direct 
  bearing 
  on 
  the 
  question 
  here 
  

   under 
  consideration. 
  

  

  2 
  The 
  chlorite 
  is 
  noticed 
  by 
  Delesse, 
  who 
  states 
  that 
  it 
  differs 
  from 
  the 
  variety 
  

   formed 
  from 
  garnet 
  in 
  the 
  Zdblitz 
  rock, 
  being 
  less 
  rich 
  in 
  iron 
  : 
  Annales 
  des 
  

   Mines, 
  ser. 
  4, 
  vol. 
  xviii. 
  (1850) 
  p. 
  327. 
  

  

  3 
  Geol. 
  Mag. 
  1895, 
  pp. 
  497, 
  498. 
  This 
  mica 
  seems 
  to 
  undergo 
  change 
  to 
  

   vaalite 
  or 
  to 
  silvery 
  spangles. 
  

  

  4 
  For 
  the 
  loan 
  of 
  this 
  and 
  other 
  slides 
  from 
  Portsoy 
  I 
  am 
  indebted 
  to 
  Prof. 
  

   Bonney. 
  

  

  