﻿Report 
  of 
  the 
  State 
  Geologist. 
  639 
  

  

  be 
  considered 
  such. 
  Granulite 
  is 
  here 
  used 
  in 
  the 
  German 
  sense 
  

   and 
  the 
  rocks 
  are 
  practically 
  identical 
  with 
  the 
  Saxon 
  ones. 
  

  

  III. 
  A 
  series 
  of 
  rocks 
  of 
  the 
  gabbro 
  family, 
  ranging 
  from 
  pure 
  

   aggregates 
  of 
  labradorite, 
  through 
  varieties 
  with 
  increasing 
  

   amounts 
  of 
  dark 
  silicates, 
  to 
  basic 
  olivine-gabbros. 
  The 
  vari- 
  

   eties 
  rich 
  in 
  feldspar 
  are 
  here 
  called 
  anorthosite, 
  following 
  the 
  

   Canadian 
  practice, 
  in 
  which 
  country 
  these 
  rocks 
  are 
  strongly 
  

   developed. 
  The 
  basic 
  varieties 
  are 
  called 
  gabbro. 
  This 
  group 
  

   has 
  been 
  previously 
  called 
  labradorite 
  rock, 
  hypersthene 
  rock, 
  

   norite 
  (this 
  most 
  commonly 
  in 
  New 
  York 
  State), 
  etc., 
  but 
  the 
  

   first 
  is 
  not 
  a 
  good 
  rock 
  name, 
  and 
  as 
  for 
  the 
  terms 
  involving 
  

   hypersthene, 
  microscopic 
  study 
  proves 
  this 
  mineral 
  to 
  be 
  much 
  

   less 
  common 
  than 
  either 
  green 
  monoclinic 
  pyroxene 
  or 
  horn- 
  

   blende, 
  and 
  much 
  of 
  it 
  seems 
  to 
  be 
  of 
  secondary 
  origin 
  in 
  the 
  

   " 
  reaction 
  series 
  " 
  around 
  olivine. 
  The 
  rocks 
  of 
  this 
  series 
  have 
  

   in 
  almost 
  all 
  cases 
  suffered 
  severely 
  from 
  dynamic 
  disturbances 
  

   and 
  few 
  exposures 
  fail 
  to 
  reveal 
  it. 
  The 
  pure 
  anorthosites 
  have 
  

   the 
  large 
  labradorite 
  crystals 
  crushed 
  around 
  their 
  edges 
  and 
  

   appearing 
  only 
  as 
  nuclei 
  in 
  the 
  midst 
  of 
  this 
  breccia. 
  They 
  are 
  

   especially 
  developed 
  in 
  the 
  interior 
  mountains. 
  The 
  varieties 
  pro- 
  

   vided 
  with 
  dark 
  silicates 
  often 
  have 
  a 
  gneissoid 
  structure 
  from 
  

   the 
  alignment 
  of 
  these 
  in 
  streaks. 
  The 
  pyroxene 
  in 
  such 
  cases 
  

   has 
  large] 
  y 
  given 
  way 
  to 
  hornblende 
  and 
  around 
  both, 
  often 
  

   replacing 
  them 
  almost 
  entirely, 
  are 
  rims 
  of 
  garnet. 
  The 
  dark 
  

   olivine 
  gabbros 
  have 
  never-failing 
  reaction 
  rims 
  around 
  the 
  

   olivine 
  and 
  pyroxene, 
  and 
  often 
  pass 
  into 
  thinly 
  laminated 
  gneiss. 
  

   This 
  gneissoid 
  development 
  occasions 
  the 
  great 
  stratigraphic 
  

   difficulty 
  of 
  the 
  region, 
  for 
  while 
  the 
  typical 
  representatives 
  of 
  

   both 
  series 
  I 
  and 
  series 
  III 
  are 
  readily 
  recognized, 
  the 
  gneissoid 
  

   varieties 
  of 
  the 
  latter 
  are 
  very 
  difficult 
  to 
  classify. 
  They 
  occur 
  

   as 
  intruded 
  sheets 
  in 
  the 
  gneiss, 
  now 
  infolded 
  in 
  its 
  mass, 
  as 
  dikes 
  

   and 
  as 
  great 
  outlying 
  knobs 
  and 
  masses. 
  They 
  also 
  penetrate 
  

   the 
  limestone 
  series, 
  and 
  have 
  powerfully 
  metamorphosed 
  its 
  

   beds. 
  

  

  The 
  petrographic 
  characters 
  of 
  these 
  gabbroitic 
  rocks 
  as 
  shown 
  

   along 
  the 
  lake 
  front, 
  have 
  been 
  described 
  by 
  J. 
  F. 
  Kemp 
  in 
  

   Bulletin 
  Y 
  of 
  the 
  Geological 
  Society 
  of 
  America, 
  Boston 
  meeting, 
  

   December, 
  1893. 
  

  

  The 
  rocks 
  of 
  this 
  series 
  contain 
  the 
  titaniferous 
  iron 
  ores. 
  

  

  