﻿Hansome 
  — 
  New 
  OccuTrence 
  of 
  Nepheline 
  Syenite. 
  425 
  

  

  with 
  an 
  occasional 
  movable 
  bubble, 
  and 
  capillary 
  crystals 
  of 
  

   rutile 
  (?) 
  Apatite 
  in 
  stont 
  colorless 
  prisms 
  is 
  a 
  fairly 
  abundant 
  

   accessory 
  constituent. 
  Titanite 
  occurs 
  as 
  idiomorphic 
  crystals, 
  

   but 
  more 
  commonly 
  as 
  rounded 
  or 
  irregular 
  grains. 
  There 
  is 
  a 
  

   little 
  iron 
  ore 
  present, 
  usually 
  associated 
  with 
  the 
  am 
  phi 
  bole 
  

   areas. 
  

  

  Hornblende 
  Gixtnite. 
  — 
  The 
  specimen 
  described 
  under 
  this 
  

   head 
  was 
  supposed, 
  when 
  collected, 
  to 
  be 
  merely 
  a 
  fresher 
  

   facies 
  of 
  the 
  hornblende 
  syenite, 
  as 
  its 
  richness 
  in 
  quartz 
  was 
  

   not 
  apparent 
  in 
  the 
  hand-specimen. 
  It 
  appeared 
  in 
  the 
  field 
  to 
  

   form 
  a 
  part 
  of 
  the 
  same 
  small 
  mass 
  in 
  the 
  trap 
  which 
  afforded 
  

   the 
  specimens 
  of 
  syenite 
  just 
  described. 
  It 
  is 
  a 
  medium 
  

   granular, 
  dark 
  gray 
  rock, 
  in 
  which 
  the 
  feldspars 
  are 
  brownish 
  

   in 
  color, 
  and 
  show 
  a 
  tendency 
  toward 
  prismatic 
  development 
  

   in 
  the 
  direction 
  of 
  the 
  edge 
  pA.m. 
  The 
  dark 
  constituent, 
  

   apparently 
  dark 
  green 
  hornblende, 
  is 
  fairly 
  abundant 
  in 
  rather 
  

   irregular 
  prisms. 
  A 
  little 
  dark 
  mica 
  is 
  also 
  visible 
  in 
  the 
  

   hand-specimen. 
  Under 
  the 
  microscope 
  partly 
  idiomorphic 
  

   sections 
  of 
  decomposed 
  feldspar 
  and 
  irregular 
  plates 
  of 
  amphi- 
  

   bole 
  lie 
  in 
  a 
  sort 
  of 
  gi'oundmass 
  composed 
  of 
  quartz 
  and 
  

   feldspar 
  micropegmatitically 
  intergrown. 
  The 
  idiomorphic 
  

   feldspars 
  appear 
  to 
  be, 
  in 
  part 
  at 
  least, 
  an 
  acid 
  oligoclase, 
  bnt 
  

   many 
  of 
  them 
  are 
  completely 
  changed 
  into 
  very 
  fine 
  sericitic 
  

   aggregates. 
  The 
  hornblende 
  is 
  the 
  common 
  green 
  variety 
  and 
  

   presents 
  no 
  unusual 
  features. 
  The 
  most 
  striking 
  thing 
  about 
  

   the 
  thin-section 
  is 
  the 
  beautiful 
  manner 
  in 
  which 
  the 
  quartz 
  

   and 
  feldspar, 
  together 
  constituting 
  more 
  than 
  half 
  the 
  rock, 
  

   are 
  intergrown. 
  The 
  feldspar 
  of 
  these 
  intergrowths 
  is 
  rendered 
  

   turbid 
  by 
  numerous 
  brownish 
  dust-like 
  particles, 
  and 
  its 
  char- 
  

   acter 
  is 
  not 
  easily 
  determined 
  by 
  optical 
  means 
  alone. 
  It 
  is, 
  

   however, 
  without 
  much 
  doubt 
  an 
  alkali 
  feldspar 
  closely 
  related 
  

   to 
  soda 
  orthoclase 
  or 
  to 
  anorthoclase, 
  although 
  it 
  may 
  be 
  in 
  

   part 
  ordinary 
  orthoclase. 
  It 
  shows 
  occasionally 
  the 
  tine 
  irregu- 
  

   lar 
  twinning 
  and 
  lack 
  of 
  optical 
  homogeneity 
  which 
  charac- 
  

   terize 
  anorthoclase. 
  The 
  quartz 
  is 
  always 
  more 
  or 
  less 
  

   intergrown 
  with 
  feldspar, 
  but 
  sometimes 
  shows 
  homogeneous 
  

   patches 
  of 
  considerable 
  size. 
  

  

  The 
  Trap-roch. 
  — 
  The 
  intrusive 
  mass 
  forming 
  Mt. 
  Gilboa 
  is 
  

   fairly 
  uniform 
  throughout. 
  It 
  is 
  commonly 
  a 
  dark 
  gray 
  rock 
  

   of 
  fine 
  to 
  medium 
  grain, 
  and 
  the 
  structure, 
  as 
  visible 
  to 
  the 
  

   eye, 
  is 
  granular. 
  A 
  typical 
  specimen 
  collected 
  by 
  Mr. 
  Darton 
  

   from 
  near 
  the 
  center 
  of 
  the 
  area 
  shows 
  under 
  the 
  microscope 
  a 
  

   hypidiomorphic-granular 
  structure, 
  and 
  is 
  a 
  fairly 
  fresh 
  aggre- 
  

   gate 
  of 
  labradorite 
  {ah/in^) 
  > 
  augite 
  ^ 
  hypersthene 
  > 
  quartz 
  

   >biotite^<^iron 
  ore. 
  It 
  is 
  a 
  fine-grained 
  gabbro 
  in 
  which 
  a 
  

   brown 
  diallagic 
  augite 
  is 
  intergrown 
  with 
  subordinate 
  amounts 
  

   of 
  hypersthene 
  and 
  biotite. 
  The 
  quartz 
  was 
  the 
  last 
  mineral 
  

  

  