﻿CRYSTALLINE 
  KOCKS 
  OF 
  THE 
  MALVERN 
  HILLS. 
  497 
  

  

  (iron-oxide?) 
  being 
  formed. 
  The 
  felspar 
  contains 
  a 
  little 
  white 
  

   mica. 
  Ilmenite 
  and 
  sphene 
  are 
  present. 
  

  

  No. 
  350. 
  Idem. 
  Crushing 
  and 
  decomposition 
  carried 
  further. 
  

   Much 
  opaque 
  matter 
  in 
  the 
  shear-planes. 
  A 
  great 
  deal 
  of 
  chlorite 
  

   in 
  patches 
  and 
  parallel 
  strings. 
  Numerous 
  microliths 
  of 
  a 
  highly- 
  

   refracting 
  mineral 
  (sphene 
  ?). 
  

  

  No. 
  351. 
  Granite 
  crushed 
  into 
  a 
  mass 
  of 
  wedge-like 
  fragments. 
  

   The 
  principal 
  cracks, 
  which 
  are 
  roughly 
  parallel, 
  as 
  well 
  as 
  numerous 
  

   transverse 
  fractures, 
  are 
  filled 
  with 
  minerals, 
  of 
  which 
  chlorite 
  and 
  

   ferrite 
  are 
  by 
  far 
  the 
  most 
  abundant. 
  Here 
  and 
  there 
  in 
  the 
  

   chlorite 
  are 
  patches 
  of 
  biotite, 
  which 
  sometimes 
  surround 
  nuclei 
  

   of 
  ferrite. 
  Microliths 
  of 
  the 
  sphene 
  (?) 
  are 
  also 
  immersed 
  in 
  the 
  

   chlorite. 
  

  

  No. 
  352. 
  Granite 
  partially 
  transformed 
  into 
  gneiss. 
  The 
  slide 
  

   is 
  much 
  clearer, 
  apparently 
  because 
  of 
  a 
  certain 
  amount 
  of 
  recon- 
  

   struction. 
  The 
  wedges 
  of 
  felspar 
  and 
  quartz 
  are 
  much 
  longer 
  and 
  

   thinner, 
  and 
  many 
  of 
  the 
  cracks 
  are 
  healed 
  up. 
  There 
  is 
  still 
  some 
  

   chlorite 
  in 
  the 
  cracks, 
  with 
  black 
  mica 
  and 
  sphene 
  (?) 
  as 
  before. 
  I 
  

   cannot 
  resist 
  the 
  conclusion 
  that 
  the 
  minerals 
  in 
  the 
  cracks 
  have 
  

   been 
  introduced 
  from 
  without, 
  and 
  that 
  the 
  biotite 
  has 
  been 
  formed 
  

   out 
  of 
  the 
  chlorite. 
  This 
  rock 
  passes 
  graclatim 
  into 
  a 
  thoroughly 
  

   foliated 
  gneiss 
  (416). 
  

  

  That 
  the 
  chlorite 
  and 
  ferrite 
  are 
  not 
  formed 
  out 
  of 
  the 
  granite 
  is 
  

   further 
  evident 
  from 
  slides 
  taken 
  from 
  the 
  same 
  junction 
  of 
  diorite 
  

   and 
  granite 
  at 
  a 
  few 
  feet 
  from 
  the 
  last 
  set. 
  No. 
  409 
  is 
  from 
  the 
  

   diorite 
  close 
  to 
  the 
  junction. 
  The 
  hornblende 
  is 
  decomposed 
  mainly 
  

   to 
  epidote 
  and 
  chlorite, 
  but 
  the 
  former 
  is 
  in 
  exceptionally 
  large 
  

   proportion, 
  occupying 
  about 
  one 
  fourth 
  of 
  the 
  slide. 
  It 
  is 
  in 
  small, 
  

   brightly 
  polarizing 
  granules. 
  Two 
  slides 
  (410, 
  411) 
  are 
  from 
  the 
  

   crushed 
  granite 
  within 
  a 
  few 
  inches 
  of 
  the 
  last. 
  In 
  No. 
  410 
  there 
  

   are 
  some 
  small 
  grains 
  of 
  similar 
  epidote 
  scattered 
  here 
  and 
  there 
  in 
  

   the 
  cracks 
  ; 
  but 
  in 
  No. 
  411 
  the 
  epidote 
  is 
  more 
  abundant, 
  filling 
  in 
  

   two 
  cracks 
  running 
  parallel 
  to 
  the 
  foliation, 
  one 
  of 
  which 
  opens 
  out 
  

   to 
  the 
  breadth 
  of 
  nearly 
  1*5 
  millim. 
  In 
  this 
  vein 
  the 
  epidote 
  is 
  

   crystallized 
  in 
  prisms, 
  sometimes 
  with 
  their 
  pyramidal 
  ends 
  pro- 
  

   jecting 
  into 
  a 
  water- 
  clear 
  mineral, 
  apparently 
  quartz, 
  which 
  has 
  

   filled 
  in 
  the 
  rest 
  of 
  the 
  vein. 
  

  

  It 
  is 
  thus 
  seen 
  that 
  where 
  chlorite 
  is 
  most 
  abundant 
  in 
  the 
  de- 
  

   composed 
  diorite, 
  chlorite 
  is 
  also 
  the 
  mineral 
  predominating 
  in 
  the 
  

   cracks 
  of 
  the 
  adjacent 
  granite, 
  but 
  that 
  where 
  epidote 
  is 
  most 
  con- 
  

   spicuous 
  in 
  the 
  former, 
  it 
  is 
  also 
  common 
  in 
  the 
  latter. 
  Irrespective 
  

   of 
  these 
  coincidences, 
  it 
  is 
  surely 
  incredible 
  that 
  chlorite 
  and 
  epidote 
  

   should 
  be 
  formed 
  out 
  of 
  quartz 
  and 
  a 
  potash-felspar. 
  

  

  This 
  infiltration 
  -gneiss 
  forms 
  the 
  ridge 
  for 
  a 
  hundred 
  yards 
  or 
  so. 
  

   Here 
  and 
  there 
  we 
  see 
  in 
  it 
  lenticular 
  flakes 
  of 
  granite, 
  some 
  of 
  

   which 
  are 
  several 
  inches 
  thick. 
  Sometimes 
  they 
  are 
  elongated 
  into 
  

   narrow 
  cakes. 
  At 
  first 
  sight 
  they 
  might 
  be 
  taken 
  for 
  veins 
  ; 
  but 
  I 
  

   am 
  persuaded 
  they 
  are 
  merely 
  residua 
  from 
  the 
  shearing 
  process, 
  

   representing 
  on 
  a 
  larger 
  scale 
  the 
  flattened 
  crystals 
  of 
  an 
  augen- 
  

   gneiss. 
  It 
  is 
  not 
  difficult 
  to 
  distinguish 
  these 
  residual 
  flakes 
  from 
  

  

  a 
  J. 
  G. 
  S. 
  No. 
  179. 
  2 
  n 
  

  

  