﻿AND 
  BANDED 
  CRYSTALLINE 
  ROCKS 
  OF 
  THE 
  LIZARD. 
  521 
  

  

  gical 
  sense. 
  But 
  there 
  is 
  no 
  proof 
  that 
  the 
  fragments 
  have 
  been 
  

   deposited 
  as 
  such. 
  The 
  original 
  minerals 
  may 
  have 
  been 
  broken 
  

   during 
  the 
  deformation 
  of 
  the 
  rock-masses. 
  This, 
  I 
  believe, 
  is 
  what 
  

   has 
  actually 
  taken 
  place. 
  The 
  structures 
  are 
  of 
  the 
  kind 
  for 
  which 
  

   Prof. 
  Kjerulf 
  has 
  proposed 
  the 
  term 
  cataclastic." 
  

  

  Still 
  more 
  recently 
  Mr. 
  Alexander 
  Somervail, 
  in 
  communications 
  

   to 
  the 
  ' 
  Geological 
  Magazine 
  ' 
  *, 
  asserts 
  the 
  " 
  igneous 
  origin" 
  of 
  the 
  

   whole 
  of 
  Prof. 
  Bonney's 
  granulitic 
  group, 
  and 
  he 
  points 
  to 
  the 
  dyke 
  

   in 
  serpentine 
  at 
  the 
  extreme 
  north 
  end 
  of 
  Pentreath 
  Beach 
  as 
  a 
  por- 
  

   tion 
  of 
  this 
  " 
  granulitic 
  group," 
  and 
  states 
  that, 
  " 
  at 
  the 
  west 
  end 
  of 
  

   Kennack 
  Cove, 
  the 
  dykes 
  cutting 
  the 
  serpentine 
  are 
  seen 
  to 
  coalesce 
  

   with 
  the 
  granulitic 
  rocks 
  forming 
  the 
  foreshore." 
  Mr. 
  Somervail 
  

   concludes 
  that 
  the 
  granite, 
  diorite, 
  and 
  other 
  varieties 
  of 
  rock 
  speci- 
  

   fied 
  in 
  his 
  paper 
  " 
  have 
  been 
  differentiated 
  out 
  of 
  the 
  same 
  magma 
  

   during 
  the 
  cooling 
  process, 
  the 
  ordinary 
  selective 
  law 
  of 
  chemical 
  

   affinity 
  separating 
  the 
  basic 
  from 
  the 
  acidic 
  types." 
  He 
  adds 
  in 
  a 
  

   subsequent 
  communication 
  t 
  that 
  he 
  does 
  not 
  know 
  any 
  separation 
  

   between 
  the 
  beds 
  of 
  the 
  "granulitic" 
  group 
  and 
  the 
  hornblende-schists 
  

   save 
  in 
  the 
  extremes 
  of 
  their 
  compositions." 
  

  

  The 
  above 
  extracts 
  show 
  that 
  the 
  geology 
  of 
  the 
  Lizard 
  District 
  

   is 
  still 
  in 
  a 
  very 
  unsettled 
  state 
  in 
  respect 
  to 
  some 
  material 
  points. 
  

  

  Hornblende-schists. 
  

  

  I 
  pass 
  on 
  now 
  to 
  offer 
  some 
  remarks 
  on 
  the 
  hornblende-schists. 
  

  

  These 
  rocks, 
  in 
  the 
  area 
  covered 
  by 
  this 
  paper, 
  namely 
  the 
  coast- 
  

   line 
  from 
  the 
  Lion 
  Bock, 
  Kynance 
  Cove, 
  on 
  the 
  west 
  coast, 
  to 
  

   Kennack 
  Cove 
  on 
  the 
  east 
  coast, 
  are 
  bedded 
  crystalline 
  schists 
  in 
  

   which 
  the 
  foliation 
  is 
  strictly 
  parallel 
  to 
  the 
  bedding. 
  The 
  dip 
  is, 
  

   on 
  the 
  whole, 
  very 
  flat, 
  and 
  being 
  nearly 
  flat 
  it 
  wavers 
  about 
  con- 
  

   siderably, 
  ranging 
  from 
  W.N.E. 
  (magnetic) 
  round 
  by 
  E.N.E. 
  and 
  

   E. 
  to 
  S.S.E. 
  

  

  The 
  following 
  table 
  (p. 
  522) 
  gives 
  a 
  summary 
  of 
  the 
  result 
  of 
  the 
  

   microscopic 
  examination 
  of 
  16 
  samples 
  of 
  schists 
  from 
  the 
  horn- 
  

   blende-schist 
  area. 
  

  

  The 
  first 
  point 
  to 
  be 
  noted, 
  and 
  the 
  result 
  was 
  a 
  surprise 
  to 
  me, 
  

   is 
  that 
  none 
  of 
  the 
  samples 
  entered 
  in 
  the 
  above 
  list 
  contain 
  quartz. 
  

   In 
  this 
  respect 
  they 
  present 
  a 
  striking 
  contrast 
  to 
  the 
  rocks 
  of 
  the 
  

   granulitic 
  group 
  (a 
  microscopic 
  analysis 
  of 
  which 
  is 
  given 
  further 
  

   on, 
  p. 
  532) 
  and 
  the 
  rocks 
  of 
  the 
  metamorphic 
  series 
  below 
  the 
  horn- 
  

   blende-schists. 
  

  

  The 
  next 
  point 
  to 
  be 
  observed 
  is 
  that 
  all 
  the 
  samples, 
  without 
  

   exception, 
  contain 
  felspar. 
  This 
  mineral 
  forms 
  the 
  base 
  in 
  which 
  

   the 
  other 
  minerals 
  are 
  set 
  ; 
  much 
  of 
  it 
  exhibits 
  the 
  twinning 
  of 
  the 
  

   triclinic 
  system, 
  but, 
  as 
  a 
  rule, 
  it 
  is 
  much 
  kaolinized 
  or 
  in 
  other 
  ways 
  

   altered. 
  Here 
  and 
  there 
  it 
  is 
  water-clear, 
  but 
  the 
  presence 
  of 
  poly- 
  

   synthetic 
  twinning, 
  or 
  the 
  character 
  of 
  the 
  interference 
  figure 
  in 
  con- 
  

   verging 
  polarized 
  light, 
  shows 
  conclusively 
  that 
  the 
  clear 
  mineral 
  is 
  

   felspar 
  and 
  not 
  quartz. 
  

  

  * 
  Geol. 
  Mag. 
  1888, 
  pp. 
  46, 
  553. 
  

   t 
  Ibid. 
  1889, 
  p. 
  96. 
  

  

  