﻿424 
  Ransome 
  — 
  New 
  Occurrence 
  of 
  Nejpheline 
  Syenite. 
  

  

  alkali 
  feldspars 
  containing 
  both 
  soda 
  and 
  potash 
  molecules. 
  

   There 
  is 
  probably 
  a 
  little 
  acid 
  oligoclase 
  present 
  with 
  the 
  other 
  

   feldspars. 
  The 
  biotite 
  is 
  in 
  the 
  main 
  fairly 
  fresh, 
  but 
  is 
  some- 
  

   times 
  partly 
  chloritized. 
  It 
  occurs 
  in 
  short 
  stout 
  prisms 
  or 
  

   thick 
  scales, 
  giving 
  abundant 
  oblong 
  sections 
  with 
  somewhat 
  

   ragged 
  ends. 
  

  

  The 
  pyroxene 
  is 
  largely 
  altered 
  to 
  calcite 
  and 
  chlorite. 
  It 
  

   shows 
  a 
  tendency 
  toward 
  idiomorphicform 
  and 
  the 
  larger 
  crys- 
  

   tals 
  frequently 
  have 
  a 
  pale 
  pinkish 
  interior 
  with 
  a 
  greenish 
  

   rim, 
  both 
  being 
  optically 
  continuous. 
  In 
  some 
  specimens 
  no 
  

   pyroxene 
  is 
  recognizable, 
  and 
  in 
  others 
  there 
  is 
  present 
  a 
  green 
  

   amphibole 
  which 
  may 
  exceed 
  the 
  pyroxene 
  in 
  amount. 
  The 
  

   rock 
  generally 
  shows 
  considerable 
  alteration, 
  which 
  renders 
  its 
  

   petrographic 
  study 
  unsatisfactory. 
  

  

  Hornhlende 
  Syenite. 
  — 
  This 
  rock, 
  which 
  occurs, 
  as 
  already 
  

   described, 
  near 
  the 
  southern 
  end 
  of 
  the 
  trap-mass, 
  just 
  north 
  

   of 
  Barbour 
  & 
  Ireland's 
  quarry, 
  is 
  a 
  coarse-grained 
  and 
  slightly 
  

   microlitic 
  aggregate 
  of 
  flesh-colored 
  feldspars 
  and 
  rather 
  

   bleached-looking 
  fibrous 
  green 
  amphibole. 
  The 
  feldspar 
  and 
  

   amphibole 
  both 
  show 
  a 
  tendency 
  toward 
  prismatic 
  develop- 
  

   ment, 
  and 
  some 
  cleavage 
  faces 
  of 
  the 
  former 
  are 
  seen 
  under 
  

   the 
  lens 
  to 
  be 
  finely 
  striated. 
  The 
  microscope 
  reveals 
  a 
  hyp- 
  

   idiomorphic-granular 
  aggregate 
  of 
  alkali 
  feldspar, 
  amphibole, 
  

   and 
  a 
  little 
  quartz. 
  The 
  alkali-feldspar 
  is 
  turbid 
  with 
  the 
  

   usual 
  brown 
  dust-like 
  particles, 
  and 
  is 
  besides 
  usually 
  full 
  of 
  

   wisps 
  of 
  secondary 
  sericite. 
  Nearly 
  all 
  the 
  feldspar 
  shows 
  

   fine 
  polysynthetic 
  twinning, 
  corresponding 
  to 
  both 
  the 
  albite 
  

   and 
  pericline 
  laws. 
  But 
  the 
  twinning 
  is 
  often 
  very 
  irregular, 
  

   occupying 
  only 
  a 
  portion 
  of 
  an 
  individual 
  grain, 
  and 
  is 
  some- 
  

   times 
  associated 
  with 
  tine 
  microperthitic 
  intergrowths. 
  Some 
  

   acid 
  soda-lime 
  feldspar 
  (oligoclase) 
  may 
  possibly 
  be 
  present, 
  

   but 
  the 
  bulk 
  of 
  the 
  feldspar 
  is 
  probably 
  an 
  alkali-feldspar 
  iden- 
  

   tical 
  with, 
  or 
  closely 
  related 
  to, 
  anorthoclase. 
  The 
  index 
  of 
  

   refraction 
  is 
  in 
  all 
  cases 
  lower 
  than 
  the 
  balsam. 
  The 
  abundant 
  

   secondary 
  sericite, 
  and 
  absence 
  of 
  calcite, 
  suggest 
  that 
  the 
  lime 
  

   molecule 
  must 
  occupy 
  a 
  very 
  subordinate 
  position 
  in 
  the 
  com- 
  

   position 
  of 
  the 
  feldspars. 
  

  

  The 
  amphibole 
  is 
  pale 
  yellowish 
  green, 
  and 
  occurs 
  in 
  allo- 
  

   triomorphic 
  areas 
  between 
  the 
  feldspars. 
  In 
  a 
  few 
  instances 
  

   the 
  amphibole 
  is 
  compact, 
  but 
  it 
  usually 
  shows 
  a 
  distinct 
  

   fibrous 
  structure, 
  each 
  area 
  being 
  made 
  up 
  of 
  bundles 
  of 
  

   numerous 
  slender 
  prisms, 
  not 
  all 
  of 
  which 
  are 
  in 
  parallel 
  

   orientation. 
  The 
  pleochroism 
  is 
  n 
  pale 
  yellowish 
  green, 
  bdark 
  

   yellowish 
  green, 
  and 
  c 
  pale 
  green. 
  The 
  absorption 
  is 
  b>cl>a. 
  

   The 
  optical 
  scheme 
  is 
  the 
  usual 
  one 
  a 
  = 
  a^h 
  = 
  b, 
  and 
  C/\C 
  — 
  at 
  

   least 
  16°. 
  Quartz 
  occurs* 
  in 
  subordinate 
  amount 
  as 
  irregular 
  

   clear 
  grains 
  between 
  the 
  feldspars. 
  It 
  contains 
  fluid 
  cavities 
  

  

  