﻿104 
  Thirtieth 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  a. 
  This 
  section 
  is 
  peculiar, 
  differing 
  from 
  all 
  those 
  which 
  

   follow 
  as 
  strikingly 
  as 
  the 
  rock 
  itself 
  from 
  the 
  remainder 
  of 
  the 
  

   collection. 
  It 
  is 
  of 
  a 
  reddish 
  color, 
  interrupted 
  by 
  apparently 
  

   blank 
  spaces, 
  and 
  spotted 
  with 
  black 
  opaque 
  spots. 
  The 
  red 
  

   portion 
  is 
  divided 
  up 
  into 
  fine 
  wedge-shaped 
  masses, 
  running 
  

   one 
  into 
  another, 
  and 
  in 
  polarized 
  light 
  assuming 
  the 
  two 
  

   phases 
  alternately. 
  It 
  is 
  a 
  highly 
  twinned 
  feldspar, 
  in 
  appear- 
  

   ance 
  altogether 
  distinct 
  from 
  labradorite. 
  Numerous 
  amor- 
  

   phous 
  reddish 
  patches, 
  perhaps 
  ferric 
  oxide, 
  are 
  included 
  in 
  it, 
  

   imparting 
  the 
  color. 
  These 
  and 
  crystals 
  of 
  menaccanite 
  are 
  

   distributed 
  through 
  the 
  feldspathic 
  portion, 
  the 
  quartz 
  areas 
  

   being 
  distinguished 
  by 
  an 
  almost 
  entire 
  freedom 
  from 
  foreign 
  

   matters, 
  and 
  their 
  hexagonal 
  outline. 
  

  

  14. 
  Consists 
  mainly 
  of 
  labradorite, 
  perfectly 
  limpid 
  except 
  

   where 
  confused 
  particles 
  of 
  undetermined 
  foreign 
  matter 
  are 
  

   present. 
  These 
  are 
  distributed 
  parallel 
  to 
  the 
  masses 
  of 
  horn- 
  

   blende, 
  and 
  give 
  to 
  the 
  feldspathic 
  matrix 
  its 
  white 
  milky 
  

   appearance. 
  The 
  hornblende 
  is 
  yellowish-red 
  and 
  strongly 
  

   dichroic. 
  It 
  is 
  surrounded 
  by 
  light 
  to 
  dark-green 
  masses, 
  

   which 
  are 
  less 
  dichroic, 
  and 
  are 
  probably 
  pyroxene 
  in 
  course 
  

   of 
  alteration. 
  The 
  hornblende 
  presents 
  the 
  characteristic 
  cleav- 
  

   age 
  lines, 
  and 
  is 
  sometimes 
  in 
  twinned 
  crystals. 
  The 
  labrador- 
  

   ite 
  is 
  finely 
  banded, 
  and 
  so 
  intricately 
  twinned 
  as 
  to 
  give, 
  in 
  

   connection 
  with 
  the 
  free 
  quartz, 
  of 
  which 
  considerable 
  is 
  present, 
  

   an 
  unusually 
  beautiful 
  appearance 
  to 
  this 
  section 
  when 
  viewed 
  

   in 
  polarized 
  light. 
  

  

  It 
  is 
  of 
  great 
  interest 
  to 
  compare 
  these 
  objects, 
  occurring 
  in 
  

   the 
  norites 
  of 
  the 
  Adirondacks, 
  with 
  similar 
  ones 
  encountered 
  

   in 
  the 
  labradorites 
  (or 
  plagioclases) 
  of 
  the 
  norites 
  of 
  Sweden, 
  

   Scotland 
  and 
  elsewhere. 
  As 
  a 
  rule 
  the 
  latter 
  present 
  in 
  the 
  

   rock-section 
  a 
  tolerably 
  clear 
  field. 
  * 
  

  

  An 
  admixture 
  of 
  microliths 
  of 
  augite 
  and 
  hornblende 
  or 
  

   magnetite 
  belongs 
  to 
  the 
  less 
  usual 
  occurrences. 
  Fluid-inclu 
  

   sions 
  are 
  not 
  common. 
  But 
  in 
  the 
  plagioclase 
  of 
  the 
  norite 
  of 
  

   the 
  island 
  of 
  Mull, 
  many 
  very 
  beautiful 
  ones 
  occur, 
  and 
  also 
  in 
  

   that 
  of 
  the 
  isle 
  of 
  Skye. 
  In 
  the 
  latter, 
  are 
  also 
  black 
  and 
  

   brownish 
  translucent 
  needles, 
  sometimes 
  0.06 
  m.m. 
  long 
  and 
  

   0.004 
  m.m. 
  broad. 
  Grains 
  and 
  small 
  needles, 
  which 
  consist 
  of 
  

   granules 
  arranged 
  one 
  after 
  another, 
  and 
  also 
  small 
  plates 
  are 
  

  

  * 
  F. 
  Zirkel. 
  Die 
  mikr. 
  Beschaffenlieit 
  der 
  Min. 
  u. 
  Gesteine. 
  

  

  