﻿Yol. 
  53.] 
  STJDBCJEY 
  NICKEL 
  DISTRICT 
  (CANADA). 
  53 
  

  

  :fine-grained 
  and 
  weathers 
  to 
  a 
  greenish 
  colour. 
  Crystals 
  of 
  black 
  

   hornblende, 
  varying 
  in 
  size 
  from 
  peas 
  to 
  ' 
  marbles/ 
  are 
  richly 
  

   scattered 
  through 
  it. 
  

  

  Hocks 
  West 
  of 
  the 
  Type-rock. 
  — 
  We 
  shall 
  now 
  examine 
  in 
  turn 
  

   the 
  rocks 
  collected 
  along 
  the 
  railway 
  between 
  the 
  type-rock 
  and 
  

   the 
  north-western 
  contact. 
  

  

  About 
  J 
  mile 
  north-west 
  of 
  the 
  type-rock, 
  there 
  seems 
  to 
  be 
  

   little 
  change 
  macroscopically. 
  Small 
  sapphire-bine 
  grains 
  of 
  quartz 
  

   are 
  frequently 
  observed 
  in 
  the 
  dark 
  rock. 
  The 
  microscope 
  shows 
  

   the 
  complete 
  alteration 
  of 
  hypersthene 
  to 
  bastite 
  and 
  green 
  horn- 
  

   hlende. 
  The 
  boundaries 
  of 
  the 
  secondary 
  products 
  are 
  fairly 
  sharp, 
  

   although 
  there 
  has 
  been 
  considerable 
  migration 
  of 
  hornblende. 
  

   Frequently 
  the 
  secondary 
  hornblende 
  is 
  associated 
  with 
  scales 
  of 
  

   biotite, 
  as 
  if 
  the 
  latter 
  had 
  been 
  produced 
  from 
  the 
  former. 
  Within 
  

   the 
  bounds 
  of 
  the 
  old 
  hypersthene-areas 
  the 
  hornblende 
  extinguishes 
  

   in 
  two 
  portions, 
  and 
  presents 
  in 
  some 
  cases, 
  between 
  crossed 
  nicols, 
  

   the 
  appearance 
  of 
  polysynthetic 
  twinning 
  on 
  the 
  orthopinacoid. 
  

   There 
  are 
  occasional 
  irregular 
  areas 
  of 
  secondary 
  hornblende, 
  as 
  if 
  

   derived 
  from 
  augite. 
  Primary 
  hornblende 
  and 
  biotite 
  are 
  present 
  

   in 
  about 
  the 
  same 
  proportions 
  as 
  in 
  the 
  type-specimen. 
  Micro- 
  

   pegmatite 
  forms 
  a 
  few 
  small 
  areas, 
  arid 
  seems 
  to 
  have 
  been 
  one 
  of 
  

   the 
  last 
  constituents 
  to 
  crystallize. 
  

  

  One 
  mile 
  east 
  of 
  Hayside 
  Station 
  the 
  rock 
  becomes 
  quite 
  coarse 
  

   and 
  gabbro-like. 
  The 
  dark 
  minerals 
  constitute 
  only 
  a 
  third 
  of 
  the 
  

   jock. 
  Microscopically 
  it 
  differs 
  from 
  the 
  last 
  specimen 
  in 
  the 
  total 
  

   disappearance 
  of 
  the 
  bastite 
  stage 
  of 
  secondary 
  hornblende, 
  an 
  in- 
  

   crease 
  in 
  fine 
  scaly 
  biotite 
  in 
  association 
  with 
  immigrated 
  hornblende, 
  

   and 
  an 
  abundance 
  of 
  epidote-crystals 
  in 
  the 
  plagioclases. 
  The 
  

   original 
  rock 
  was 
  of 
  a 
  somewhat 
  more 
  acid 
  character 
  than 
  those 
  

   previously 
  examined, 
  as 
  indicated 
  by 
  an 
  increase 
  in 
  the 
  quantity 
  of 
  

   quartz 
  and 
  micropegmatite. 
  There 
  are 
  a 
  few 
  grains 
  of 
  a 
  mineral 
  

   which 
  is 
  strongly 
  pleochroic 
  — 
  purple, 
  rose, 
  colourless 
  — 
  and 
  which 
  is 
  

   generally 
  associated 
  with 
  the 
  bisilicates. 
  It 
  is 
  probably 
  orthite. 
  

  

  Westward 
  the 
  rock 
  takes 
  on 
  gradually 
  the 
  appearance 
  of 
  a 
  granite. 
  

   The 
  weathered 
  surface 
  is 
  white 
  to 
  pink 
  instead 
  of 
  green, 
  while 
  an 
  

   indistinct 
  parallelism 
  is 
  sometimes 
  noticeable. 
  Fine 
  scaly 
  biotite 
  is 
  

   more 
  prominent, 
  while 
  the 
  large, 
  bright, 
  black 
  cleavage-surfaces 
  of 
  

   hypersthene, 
  biotite, 
  and 
  hornblende 
  are 
  seldom 
  observed. 
  

  

  A 
  specimen 
  collected 
  about 
  J 
  mile 
  west 
  of 
  Payside 
  Station 
  repre- 
  

   sents 
  the 
  north-western 
  border 
  of 
  the 
  area. 
  The 
  weathered 
  surface 
  

   is 
  pale 
  pink. 
  Parallelism 
  in 
  the 
  constituents 
  is 
  very 
  apparent, 
  so 
  

   that 
  the 
  structure 
  is 
  coarsely 
  gneissoid. 
  The 
  texture 
  is 
  finer 
  than 
  

   in 
  the 
  central 
  portion 
  of 
  the 
  eruptive. 
  The 
  microscope 
  shows 
  that 
  

   fine 
  scaly 
  biotite 
  is 
  the 
  only 
  bisilicate 
  present, 
  that 
  orthoclase 
  is 
  

   much 
  more 
  abundant 
  than 
  plagioclase, 
  and 
  that 
  quartz 
  in 
  small 
  

   grains 
  makes 
  up 
  about 
  half 
  the 
  rock. 
  This 
  granitic 
  rock 
  has 
  been 
  

   subjected 
  to 
  considerable 
  pressure, 
  as 
  indicated 
  by 
  the 
  undulatory 
  

   extinction 
  of 
  the 
  quartz-grains 
  and 
  the 
  bending 
  and 
  breaking 
  of 
  the 
  

   jDiagioclase-crystals. 
  

  

  Quite 
  at 
  the 
  contact, 
  in 
  a 
  hill 
  | 
  mile 
  north-west 
  of 
  Rayside 
  

  

  