﻿Vol. 
  53-] 
  SUDBURY 
  NICKEL 
  DISTRICT 
  ( 
  CANADA). 
  49 
  

  

  outline 
  or 
  cleavage, 
  and 
  finally 
  the 
  hornblende 
  in 
  question 
  with 
  

   definite 
  outline, 
  strong 
  pleochroism, 
  and 
  characteristic 
  cleavage. 
  

   Were 
  this 
  the 
  case 
  we 
  should 
  expect 
  to 
  find 
  the 
  largest 
  amounts 
  of 
  

   this 
  hornblende 
  in 
  rocks 
  where 
  alteration 
  had 
  advanced 
  farthest. 
  

   This, 
  however, 
  as 
  will 
  be 
  seen 
  later, 
  is 
  not 
  the 
  case, 
  and 
  hence 
  it 
  is 
  

   preferable 
  to 
  regard 
  this 
  well-developed 
  hornblende 
  as 
  primary, 
  and 
  

   as 
  having 
  formed 
  borders 
  on 
  the 
  pyroxene-crystals 
  in 
  the 
  original 
  

   unaltered 
  norite. 
  When 
  so 
  regarded, 
  we 
  find 
  difficulty 
  neither 
  in 
  

   explaining 
  its 
  presence 
  as 
  a 
  border 
  on 
  perfectly 
  fresh 
  hypersthene- 
  

   crystals, 
  nor 
  in 
  its 
  surrounding 
  the 
  bluish-green 
  hornblende, 
  which 
  

   is 
  undoubtedly 
  of 
  secondary 
  nature. 
  

  

  Biotite 
  is 
  occasionally 
  observed 
  in 
  well-developed 
  scales, 
  of 
  whose 
  

   primary 
  nature 
  there 
  is 
  no 
  doubt. 
  Secondary 
  hornblende 
  forms 
  

   a 
  very 
  narrow 
  border 
  on 
  biotite-scales 
  when 
  in 
  contact 
  with 
  

   plagioclase. 
  

  

  Apatite, 
  magnetite, 
  and 
  occasionally 
  grains 
  of 
  iron 
  sulphides 
  are 
  

   present, 
  as 
  is 
  usually 
  the 
  case 
  in 
  such 
  rocks. 
  The 
  very 
  last 
  

   mineral 
  to 
  crystallize 
  was 
  quartz, 
  which 
  is 
  represented 
  by 
  a 
  few 
  

   irregular 
  grains. 
  

  

  Prom 
  this 
  description 
  it 
  will 
  be 
  seen 
  that 
  the 
  type-rock 
  of 
  the 
  

   nickel-bearing 
  eruptive 
  exposed 
  between 
  Murray 
  and 
  Rayside 
  

   Stations 
  is 
  a 
  norite 
  containing 
  small 
  quantities 
  of 
  biotite, 
  hornblende, 
  

   and 
  augite. 
  The 
  slight 
  alteration 
  in 
  no 
  way 
  obscures 
  the 
  original 
  

   nature 
  of 
  the 
  rock. 
  

  

  East 
  of 
  the 
  Type-rock. 
  — 
  Eastward 
  along 
  the 
  railway 
  very 
  little 
  

   change 
  is 
  observed 
  in 
  the 
  character 
  of 
  the 
  greenstone 
  for 
  some 
  

   distance. 
  About 
  \ 
  mile 
  east 
  of 
  the 
  type-rock 
  two 
  intrusions 
  of 
  

   granite 
  occur. 
  The 
  broader 
  of 
  these 
  has 
  a 
  width 
  of 
  about 
  100 
  

   yards. 
  The 
  later 
  age 
  of 
  this 
  granite 
  may 
  be 
  concluded, 
  as 
  it 
  sends 
  

   apophyses 
  into 
  the 
  norite, 
  and 
  where 
  in 
  contact 
  with 
  the 
  latter 
  

   rock 
  it 
  has 
  changed 
  the 
  pyroxenes 
  to 
  hornblende 
  and 
  biotite. 
  

   Similar 
  action 
  may 
  be 
  observed 
  on 
  fragments 
  of 
  norite 
  included 
  in 
  

   the 
  granite. 
  This 
  intrusive 
  granite 
  will 
  be 
  fully 
  described 
  later. 
  

   It 
  is 
  enough 
  here 
  to 
  know 
  that 
  we 
  have 
  sufficient 
  ground 
  for 
  

   regarding 
  the 
  norite 
  as 
  a 
  continuous 
  area. 
  

  

  About 
  | 
  mile 
  east 
  of 
  the 
  type-rock 
  the 
  rock 
  is 
  macroscopically 
  

   unchanged, 
  except 
  that 
  it 
  peels 
  off 
  in 
  concentric 
  layers 
  when 
  exposed 
  

   to 
  the 
  weather, 
  as 
  is 
  frequently 
  the 
  case 
  with 
  diabase, 
  but 
  not 
  with 
  

   norite. 
  The 
  microscope 
  shows 
  that 
  it 
  is 
  more 
  altered 
  than 
  the 
  

   type-rock. 
  Most 
  of 
  the 
  hypersthene-crystals 
  are 
  so 
  altered 
  that 
  

   generally 
  only 
  a 
  few 
  isolated 
  grains 
  can 
  be 
  detected 
  in 
  areas 
  of 
  

   secondary 
  hornblende, 
  whose 
  areas 
  are 
  identical 
  with 
  those 
  of 
  the 
  

   normal 
  hypersthene-crystals. 
  The 
  secondary 
  hornblende 
  is 
  the 
  

   same 
  as 
  in 
  the 
  previous 
  rock, 
  except 
  that 
  there 
  is 
  relatively 
  more 
  

   pale 
  bluish-green 
  hornblende 
  and 
  less 
  bastite. 
  

  

  A 
  few 
  needles 
  of 
  secondary 
  pale-green 
  hornblende 
  occur 
  in 
  the 
  

   plagioclase, 
  ^s 
  if 
  the 
  bastite-substanee 
  had 
  been 
  transported 
  into 
  

   the 
  felspar, 
  aud 
  had 
  there 
  produced 
  the 
  pale 
  green 
  hornblende, 
  

   which 
  in 
  the 
  type-rock 
  occurred 
  only 
  where 
  bastite 
  bordered 
  on 
  

   felspar. 
  The 
  plagioclase 
  constitutes 
  two-thirds 
  of 
  the 
  rock, 
  and, 
  

  

  Q.J.G.S. 
  No. 
  209. 
  e 
  

  

  