﻿Yol. 
  53.] 
  SUDBURY 
  NICKEL 
  DISTRICT 
  (CANADA). 
  63 
  

  

  so 
  that 
  the 
  total 
  quantity 
  of 
  pyroxene 
  and 
  olivine 
  is 
  nearly 
  constant. 
  

   The 
  olivine 
  forms 
  more 
  or 
  less 
  rounded, 
  pale 
  greenish-yellow 
  grains, 
  

   which 
  are 
  younger 
  than 
  the 
  plagioclase, 
  but 
  older 
  than 
  the 
  augite. 
  

   Sometimes 
  the 
  olivine 
  has 
  given 
  rise 
  to 
  small 
  quantities 
  of 
  serpentine 
  

   and 
  swarms 
  of 
  minute 
  grains 
  of 
  magnetite. 
  The 
  pyroxene 
  shows 
  

   no 
  definite 
  outline, 
  and 
  very 
  seldom 
  imperfect 
  cleavage 
  : 
  it 
  is 
  reddish- 
  

   Thrown 
  to 
  violet 
  in 
  colour, 
  and 
  distinctly 
  pleochroic. 
  The 
  usual 
  

   accessory 
  minerals 
  are 
  present, 
  and 
  the 
  rock 
  is 
  remarkably 
  fresh. 
  

  

  One 
  point 
  characteristic 
  of 
  these 
  dykes 
  is 
  the 
  ease 
  with 
  which 
  

   they 
  are 
  acted 
  upon 
  by 
  hydrochemical 
  agencies. 
  Near 
  the 
  village 
  

   of 
  Murray 
  Mines 
  the 
  Government 
  road 
  passes 
  for 
  some 
  distance 
  

   between 
  high 
  walls 
  of 
  granite, 
  which 
  have 
  become 
  prominent 
  by 
  the 
  

   weathering-out 
  of 
  the 
  diabase. 
  The 
  nickel-bearing 
  greenstones 
  

   resist 
  the 
  action 
  of 
  atmospheric 
  agencies 
  much 
  better, 
  and 
  are 
  

   generally 
  greenish 
  on 
  the 
  weathered 
  surface. 
  In 
  this 
  respect 
  they 
  

   stand 
  in 
  contrast 
  to 
  the 
  rocks 
  under 
  discussion, 
  which 
  become 
  quite 
  

   rusty 
  on 
  exposure. 
  Spheroidal 
  weathering 
  is 
  characteristic. 
  

  

  One 
  of 
  the 
  exposures 
  on 
  the 
  railway 
  immediately 
  east 
  of 
  

   Worthington 
  Station 
  contains 
  porphyritic 
  crystals 
  of 
  plagioclase 
  

   from 
  1 
  to 
  2 
  inches 
  long.' 
  This 
  porphyritic 
  phase 
  is 
  confined 
  to 
  

   within 
  2 
  yards 
  of 
  the 
  contact. 
  No 
  glassy 
  borders 
  were 
  observed 
  in 
  

   connexion 
  with 
  these 
  dykes, 
  but 
  this 
  may 
  be 
  due 
  to 
  the 
  ease 
  with 
  

   which 
  the 
  rock 
  decays. 
  The 
  large 
  dyke, 
  where 
  exposed 
  on 
  Earns 
  ay 
  

   Lake, 
  exhibits 
  a 
  gradual 
  change 
  in 
  texture 
  from 
  very 
  fine 
  at 
  the 
  

   borders 
  to 
  quite 
  coarse 
  in 
  the 
  central 
  portions. 
  A 
  microscopic 
  

   examination 
  of 
  the 
  marginal 
  and 
  central 
  portions 
  shows 
  that 
  they 
  

   are 
  mineralogically 
  identical, 
  and 
  that 
  there 
  has 
  been 
  no 
  differen- 
  

   tiation. 
  This 
  is 
  confirmed 
  by 
  specific-gravity 
  determinations 
  of 
  a 
  

   series 
  of 
  specimens 
  representing 
  a 
  cross-section 
  of 
  the 
  dyke 
  where 
  

   its 
  width 
  is 
  about 
  40 
  yards. 
  

  

  A 
  quantitative 
  analysis 
  of 
  a 
  specimen 
  from 
  the 
  big 
  dyke 
  near 
  

   Murray 
  Mines 
  gave 
  the 
  following 
  result 
  : 
  — 
  

  

  Si0 
  2 
  47-22 
  

  

  A1 
  2 
  3 
  1652 
  

  

  Fe 
  3 
  3-32 
  

  

  FeO 
  12-40 
  

  

  MnO 
  004 
  

  

  CaO 
  961 
  

  

  MgO 
  3-33 
  

  

  K 
  2 
  0-67 
  

  

  Na 
  2 
  3-40 
  

  

  Ti0 
  2 
  3-62 
  

  

  P„0 
  5 
  0-33 
  

  

  BaO 
  001 
  

  

  CuO 
  trace 
  

  

  NiO 
  00275 
  

  

  CoO 
  00055 
  

  

  Loss 
  by 
  ignition 
  0-30 
  

  

  Total 
  , 
  100-803 
  

  

  Specific 
  gravity 
  3-01 
  

  

  