﻿478 
  

  

  DR. 
  C. 
  CALLAWAY 
  ON 
  SECONDARY 
  MINERALS 
  IN 
  THE 
  

  

  E. 
  Schistosity 
  in 
  Veined 
  Complexes. 
  

  

  The 
  most 
  important 
  phenomena 
  occur 
  in 
  masses 
  of 
  diorite 
  inter- 
  

   laced 
  with 
  granite 
  veins 
  and 
  subjected 
  to 
  pressure. 
  

  

  1. 
  Production 
  in 
  Diorite 
  of 
  Black 
  Mica, 
  White 
  Mica, 
  Quartz, 
  and 
  

   Secondary 
  Felspar. 
  

  

  Shear-zone 
  above 
  West 
  Malvern 
  (Fig. 
  1). 
  — 
  This 
  section 
  is 
  seen 
  

   in 
  the 
  uppermost 
  of 
  several 
  quarries 
  at 
  the 
  more 
  southerly 
  of 
  the 
  

   two 
  paths 
  which 
  cross 
  over 
  the 
  ridge 
  to 
  Great 
  Malvern. 
  In 
  the 
  

   lower 
  quarries 
  the 
  rock 
  is 
  mainly 
  diorite 
  with 
  vertical 
  granite- 
  

   veins. 
  The 
  same 
  structure 
  appears 
  in 
  the 
  greater 
  part 
  of 
  the 
  

   section 
  ; 
  but 
  just 
  at 
  the 
  northern 
  extremity 
  shearing 
  sets 
  in. 
  The 
  

   diorite 
  is 
  one 
  of 
  the 
  coarse 
  varieties 
  of 
  my 
  former 
  paper, 
  and 
  is 
  

  

  Fig. 
  1. 
  — 
  Section 
  of 
  Shear-zone 
  above 
  West 
  Malvern. 
  

   N 
  (Scale 
  3 
  feet 
  to 
  1 
  inch.) 
  

  

  f>$? 
  Granite. 
  

  

  a-a. 
  Joint-surfaces, 
  facing 
  to 
  south. 
  

   s. 
  Where 
  shearing 
  commences. 
  

   v. 
  Vein 
  with 
  upper 
  part 
  sheathed 
  in 
  kersantite. 
  

   v'. 
  Vein 
  of 
  quartz 
  and 
  biotite. 
  

  

  similar 
  to 
  a 
  rock 
  described 
  by 
  Mr. 
  Rutley 
  * 
  as 
  a 
  " 
  hornblende- 
  

   gabbro." 
  In 
  its 
  normal 
  state 
  it 
  is 
  a 
  granitoid 
  compound 
  of 
  horn- 
  

   blende 
  and 
  plagioclase, 
  with 
  perhaps 
  an 
  iron-ore 
  and 
  sometimes 
  

   with 
  apatite. 
  The 
  granite 
  is 
  the 
  ordinary 
  binary 
  compound 
  of 
  

   quartz 
  and 
  red 
  orthoclase, 
  the 
  only 
  original 
  granite 
  I 
  have 
  ever 
  seen 
  

   at 
  Malvern. 
  Microcline 
  f 
  is 
  sometimes 
  found 
  in 
  it, 
  but 
  this 
  mineral 
  

   occurs 
  so 
  frequently 
  in 
  this 
  district 
  coincidently 
  with 
  crushing 
  that 
  

   I 
  suspect 
  much 
  of 
  it 
  is 
  of 
  secondary 
  origin. 
  The 
  veins 
  vary 
  in 
  thick- 
  

  

  * 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xliii. 
  p. 
  492, 
  No. 
  4. 
  

   t 
  Ibid. 
  p. 
  500, 
  No. 
  22 
  ; 
  p. 
  505, 
  No. 
  33. 
  

  

  