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  Bansoine 
  — 
  New 
  Occurrence 
  of 
  Nejjheline 
  Syenite. 
  

  

  the 
  refractive 
  indices, 
  in 
  the 
  double 
  refraction, 
  and 
  in 
  the 
  

   optical 
  orientation 
  with 
  reference 
  to 
  the 
  cleavage, 
  readily 
  serve 
  

   to 
  distinguish 
  the 
  two 
  minerals. 
  The 
  cancrinite 
  may 
  be 
  in 
  

   part 
  secondary, 
  but 
  there 
  is 
  no 
  direct 
  evidence 
  that 
  it 
  is 
  not 
  all 
  

   primary. 
  

  

  Muscovite 
  (including 
  sericite), 
  on 
  the 
  other 
  hand, 
  is 
  for 
  the 
  

   most 
  part 
  plainly 
  secondary 
  in 
  this 
  rock, 
  and 
  forms 
  a 
  consider- 
  

   able 
  part 
  of 
  the 
  iine-grained 
  aggregates 
  which 
  now 
  represent 
  

   the 
  nepheline. 
  It 
  occurs 
  also 
  as 
  a 
  decomposition 
  product 
  of 
  

   the 
  feldspars. 
  One 
  or 
  two 
  larger 
  plates 
  of 
  muscovite 
  were 
  

   noted, 
  however, 
  which 
  maj^ 
  be 
  of 
  primary 
  origin. 
  As 
  it 
  is 
  not 
  

   practicable 
  to 
  distinguish 
  optically 
  between 
  muscovite 
  and 
  

   paragonite 
  in 
  such 
  an 
  occurrence, 
  the 
  possible 
  presence 
  of 
  the 
  

   soda 
  mica 
  should 
  not 
  be 
  lost 
  sight 
  of. 
  

  

  Analcite 
  is 
  revealed 
  in 
  the 
  thin-sections 
  as 
  clear 
  colorless 
  

   isotropic 
  areas, 
  nsually 
  occupying 
  more 
  or 
  less 
  triangular 
  spaces 
  

   between 
  the 
  feldspars. 
  The 
  index 
  of 
  refraction 
  is 
  considerably 
  

   below 
  that 
  of 
  the 
  balsam. 
  The 
  mineral 
  is 
  ti*aversed 
  by 
  irregu- 
  

   lar 
  cracks 
  but 
  shows 
  no 
  cleavage. 
  It 
  is 
  sometimes 
  associated 
  

   with 
  small 
  amounts 
  of 
  a 
  colorless, 
  radially 
  fibrous 
  mineral 
  

   which 
  appears 
  to 
  be 
  natrolite. 
  Both 
  minerals 
  gelatinize 
  readily 
  

   and 
  completely 
  in 
  hydrochloric 
  acid. 
  The 
  analcite, 
  as 
  previ- 
  

   ously 
  noted, 
  also 
  occurs 
  as 
  fine 
  aggregates 
  with 
  white 
  mica. 
  

  

  Apatite 
  is 
  a 
  moderately 
  abundant 
  accessory 
  in 
  slender 
  prisms 
  

   up 
  to 
  a 
  millimeter 
  in 
  length. 
  Titanite 
  occurs 
  in 
  small 
  crystals 
  

   and 
  grains 
  but 
  is 
  not 
  abundant. 
  Fluorite 
  occurs 
  sporadically 
  

   in 
  nests 
  with 
  calcite 
  and 
  analcite 
  and 
  is 
  easily 
  recognized 
  by 
  its 
  

   pale 
  lilac 
  color. 
  It 
  is 
  without 
  much 
  doubt 
  secondary. 
  Iron 
  

   ore 
  is 
  almost 
  wanting, 
  and 
  is 
  practically 
  restricted 
  to 
  a 
  few 
  

   grains 
  of 
  magnetite 
  near, 
  or 
  included 
  in, 
  the 
  amphibole. 
  

  

  A 
  chemical 
  analysis 
  of 
  the 
  nepheline 
  syenite, 
  made 
  by 
  Mr. 
  

   George 
  Steiger 
  of 
  the 
  U. 
  S. 
  Geological 
  Survey, 
  is 
  given 
  below. 
  

   He 
  was 
  unable 
  to 
  detect 
  any 
  carbonic 
  acid, 
  and 
  for 
  this 
  reason 
  

   the 
  optical 
  properties 
  of 
  the 
  mineral 
  determined 
  as 
  cancrinite 
  

   are 
  given 
  with 
  some 
  detail 
  in 
  the 
  preceding 
  petrographic 
  

   description. 
  It 
  will 
  be 
  seen 
  that 
  the 
  analysis 
  is 
  otherwise 
  per- 
  

   fectly 
  normal 
  for 
  a 
  nepheline 
  syenite 
  relatively 
  rich 
  in 
  soda. 
  

   For 
  comparison 
  there 
  is 
  placed 
  under 
  II 
  an 
  analysis 
  of 
  the 
  Red 
  

   Hill 
  nepheline 
  syenite, 
  which 
  is 
  higher 
  in 
  silica 
  and 
  lower 
  in 
  

   alumina, 
  but 
  otherwise 
  agrees 
  fairly 
  well 
  with 
  the 
  Brookville 
  

   rock. 
  The 
  analysis 
  of 
  the 
  Beemerville 
  nepheline 
  syenite 
  is 
  

   given 
  under 
  III, 
  not 
  so 
  much 
  on 
  account 
  of 
  its 
  resemblance 
  to 
  

   the 
  Brookville 
  rock, 
  as 
  to 
  exhibit 
  the 
  contrast, 
  particularly 
  in 
  

   the 
  alkalies, 
  in 
  the 
  compositions 
  of 
  these 
  two 
  New 
  Jersey 
  

   occurrences, 
  which 
  might 
  have 
  been 
  expected 
  to 
  show 
  more 
  

   agreement. 
  

  

  