﻿252 
  MISS 
  C. 
  A. 
  RAISIN 
  ON 
  THE 
  NATTTEE 
  AND 
  [May 
  1897, 
  

  

  hornblende. 
  Although 
  the 
  original 
  hornblende-crystal 
  has 
  in 
  the 
  

   process 
  of 
  change 
  become 
  ragged 
  and 
  often 
  irregularly 
  replaced 
  at 
  

   the 
  exterior 
  by 
  the 
  mineral 
  serpentine 
  or 
  actinolite, 
  yet 
  in 
  a 
  few 
  

   cases 
  a 
  definite 
  external 
  form 
  can 
  be 
  traced. 
  An 
  idiomorphic 
  

   character 
  would 
  not 
  have 
  been 
  generally 
  acquired 
  in 
  the 
  original 
  

   crystallization 
  of 
  hornblende 
  any 
  more 
  than 
  in 
  other 
  hornblendic 
  

   peridotites 
  or 
  in 
  the 
  amphibolite 
  of 
  this 
  area. 
  The 
  pale 
  hornblende 
  

   which 
  forms 
  the 
  last-named 
  rock 
  consists 
  of 
  crystals 
  often 
  bounded 
  

   by 
  straight 
  sides 
  (generally 
  prism-faces) 
  and 
  exhibiting 
  perfect 
  

   cleavages, 
  but 
  with 
  ragged 
  ends 
  (PL 
  XVII. 
  figs. 
  4 
  & 
  5). 
  Most 
  of 
  

   the 
  mineral 
  is 
  fresh, 
  but 
  occasionally 
  it 
  is 
  broken 
  up 
  into 
  an 
  

   aggregate 
  partly 
  serpentinous, 
  partly 
  actinolitic, 
  which 
  begins 
  in 
  

   tooth-like 
  projections 
  penetrating 
  into 
  the 
  hornblende. 
  

  

  (3) 
  Enstatite 
  * 
  

  

  This 
  mineral 
  can 
  be 
  identified 
  by 
  various 
  characters. 
  It 
  exhibits 
  

   close 
  parallel 
  structure, 
  with 
  straight 
  extinction, 
  appears 
  streaked 
  

   at 
  least 
  partially 
  with 
  serpentine, 
  and 
  includes, 
  along 
  the 
  structure- 
  

   planes, 
  minute 
  tubular 
  enclosures, 
  or 
  some 
  clustered 
  brownish 
  

   crystals, 
  probably 
  perofskite. 
  The 
  enstatite 
  is 
  undergoing 
  serpenti- 
  

   nization 
  and 
  is 
  similar 
  in 
  its 
  characters 
  to 
  that 
  which 
  Weigand 
  

   describes 
  as 
  forming 
  the 
  major 
  part 
  of 
  the 
  Starkenbach 
  mass, 
  which, 
  

   partly 
  from 
  this 
  fact, 
  he 
  infers 
  to 
  have 
  an 
  origin 
  different 
  from 
  that 
  

   of 
  the 
  Rauenthal 
  rock. 
  

  

  (4) 
  Augite.* 
  

  

  Augite 
  occurs 
  in 
  one 
  slide, 
  although 
  it 
  is 
  in 
  a 
  layer 
  of 
  amphi- 
  

   bolite, 
  and 
  thus, 
  according 
  to 
  Weigand's 
  hypothesis, 
  not 
  within 
  

   an 
  original 
  peridotite. 
  The 
  augite 
  is 
  colourless, 
  fresh-looking, 
  with 
  

   well 
  -developed 
  cleavages 
  seen 
  both 
  in 
  transverse 
  and 
  in 
  longitudinal 
  

   sections. 
  The 
  crystals 
  are 
  partly 
  idiomorphic 
  (with 
  planes 
  110, 
  

   101, 
  Oil) 
  and 
  are 
  enclosed 
  within 
  the 
  hornblende. 
  

  

  (5) 
  Iron 
  Oxide. 
  

  

  Secondary 
  minerals 
  occur, 
  one 
  of 
  the 
  most 
  important 
  of 
  which 
  is 
  

   iron 
  oxide, 
  commonly 
  associated, 
  as 
  Weigand 
  describes, 
  with 
  the 
  

   chlorite, 
  and 
  often 
  in 
  the 
  form 
  of 
  haematite. 
  Other 
  minute 
  grains 
  of 
  

   iron 
  oxide 
  will 
  be 
  noticed 
  shortly 
  as 
  occurring 
  in 
  the 
  serpentine. 
  

  

  (6) 
  Perofskite* 
  

  

  In 
  connexion 
  with 
  the 
  serpentinized 
  enstatite, 
  small 
  crystals 
  

   occur 
  (about 
  *025 
  mm. 
  or 
  less 
  in 
  diameter), 
  sometimes 
  in 
  definite 
  

   cubes 
  or 
  octahedra, 
  but 
  usually 
  clustered. 
  The 
  mineral 
  is 
  clear, 
  

   colourless, 
  with 
  a 
  high 
  refraction 
  and 
  rough-looking 
  surface, 
  and 
  it 
  

   has 
  whitish 
  or 
  silvery 
  lustre 
  by 
  reflected 
  light. 
  It 
  apparently 
  is 
  

   perofskite. 
  

  

  The 
  mineral 
  within 
  the 
  chlorite 
  (as 
  mentioned 
  above) 
  has 
  very 
  

  

  