﻿Plate 
  5 
  

  

  - 
  4 
  | 
  iJIP^ 
  W. 
  J. 
  Miller, 
  photo 
  

   Photomicrographs 
  of 
  thin 
  sections 
  of 
  gabbro 
  from 
  the 
  stock 
  on 
  the 
  south 
  

   side 
  of 
  Loon 
  lake. 
  Each 
  magnified 
  15 
  diameters. 
  

  

  In 
  the 
  upper 
  figure 
  the 
  large 
  central 
  mineral 
  is 
  olivine 
  completely 
  sur- 
  

   rounded 
  by 
  successive 
  rims 
  of 
  hypersthene, 
  biotite 
  (narrow 
  and 
  dark), 
  and 
  

   garnet. 
  Surrounding 
  all 
  are 
  broad 
  laths 
  of 
  labradorite. 
  

  

  In 
  the 
  lower 
  figure 
  the 
  large, 
  black, 
  central 
  mineral 
  is 
  ilmenite, 
  followed 
  

   by 
  successive 
  rims 
  of 
  biotite, 
  hornblende, 
  garnet 
  and 
  biotite. 
  The 
  second 
  

   and 
  third 
  — 
  biotite 
  and 
  hornblende 
  — 
  rims 
  are 
  not 
  separable 
  in 
  the 
  photo- 
  

   graph. 
  Surrounding 
  all 
  are 
  labradorite 
  crystals. 
  

  

  