﻿30 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  no. 
  5 
  is 
  a 
  hornblende 
  gabbro; 
  no. 
  8 
  is 
  a 
  gabbro-diorite 
  ; 
  nos. 
  10, 
  13, 
  

   and 
  14 
  are 
  hornblende 
  syenites; 
  no. 
  11 
  is 
  a 
  monzonite; 
  and 
  no. 
  12 
  

   is 
  a 
  diorite. 
  The 
  large 
  number 
  of 
  minerals 
  — 
  sixteen 
  in 
  all 
  — 
  is 
  also 
  

   notable. 
  It 
  is 
  also 
  important 
  to 
  note 
  that 
  in 
  the 
  above 
  table, 
  nos. 
  3 
  

   and 
  4, 
  7 
  and 
  8, 
  9 
  and 
  10, 
  and 
  11 
  and 
  12, 
  respectively, 
  come 
  from 
  

   single 
  stocks. 
  

  

  The 
  predominating 
  mineral 
  is 
  feldspar 
  which 
  ranges 
  from 
  labra- 
  

   dorite 
  alone 
  in 
  some 
  rocks 
  through 
  all 
  stages, 
  to 
  those 
  rocks 
  which 
  

   are 
  rich 
  in 
  the 
  more 
  acid 
  plagioclases 
  or 
  orthoclase. 
  

  

  Hornblende, 
  generally 
  in 
  considerable 
  amount, 
  occurs 
  in 
  all 
  but 
  

   one 
  (no. 
  1) 
  of 
  the 
  rocks. 
  Sometimes 
  it 
  makes 
  up 
  a 
  fourth 
  or 
  more 
  

   of 
  the 
  whole 
  rock. 
  Much 
  of 
  the 
  hornblende 
  in 
  the 
  more 
  basic 
  rocks, 
  

   at 
  least, 
  is 
  of 
  secondary 
  origin 
  and 
  forms 
  corrosion 
  rims 
  (below 
  

   described) 
  around 
  other 
  minerals. 
  Its 
  color 
  varies 
  from 
  green 
  to 
  

   brown. 
  In 
  one 
  slide 
  many 
  examples 
  of 
  the 
  transition 
  from 
  pyroxene 
  

   to 
  hornblende 
  are 
  perfectly 
  shown. 
  

  

  Hypersthene, 
  with 
  a 
  single 
  exception 
  (no. 
  5), 
  is 
  an 
  important 
  

   constituent 
  of 
  all 
  the 
  more 
  basic 
  types. 
  It 
  is 
  almost 
  always 
  highly 
  

   granulated 
  and 
  with 
  pleochroism 
  from 
  greenish 
  gray 
  to 
  pale 
  reddish 
  

   brown. 
  

  

  Augite 
  and 
  diallage 
  of 
  greenish 
  gray 
  color 
  and 
  with 
  good 
  cleavage, 
  

   are 
  only 
  occasionally 
  present 
  and 
  rarely 
  as 
  important 
  constituents. 
  

  

  Ilmenite 
  is 
  invariably 
  present 
  in 
  amounts 
  up 
  to 
  5 
  per 
  cent 
  and 
  

   often 
  with 
  transition 
  to 
  leucoxene. 
  

  

  Pyrite 
  in 
  small 
  amount 
  seldom 
  fails. 
  

  

  Biotite 
  and 
  garnet 
  of 
  the 
  usual 
  sort, 
  though 
  mostly 
  in 
  tiny 
  flakes 
  

   or 
  grains, 
  are 
  present 
  in 
  moderate 
  quantity 
  in 
  all 
  but 
  certain 
  of 
  the 
  

   more 
  acidic 
  facies. 
  The 
  unusually 
  high 
  percentage 
  of 
  garnet 
  in 
  no. 
  4 
  

   is 
  a 
  fine-grained 
  border 
  phase 
  of 
  a 
  stock. 
  

  

  Quartz, 
  in 
  small 
  irregular 
  shaped 
  grains, 
  is 
  wholly 
  confined 
  to 
  the 
  

   acidic 
  types. 
  

  

  Zoisite, 
  in 
  small 
  stout 
  prisms, 
  sometimes 
  makes 
  up 
  about 
  1 
  per 
  cent 
  

   of 
  the 
  rock. 
  

  

  Zircon 
  and 
  apatite, 
  in 
  very 
  small 
  quantities, 
  are 
  almost 
  wholly 
  

   confined 
  to 
  the 
  acidic 
  facies. 
  The 
  usual 
  absence 
  of 
  the 
  apatite 
  from 
  

   the 
  typical 
  gabbros 
  is 
  especially 
  noteworthy. 
  

  

  Olivine 
  was 
  noted 
  in 
  but 
  one 
  case 
  (no. 
  1) 
  and 
  this 
  in 
  the 
  only 
  

   rock 
  from 
  which 
  hornblende 
  is 
  missing. 
  

  

  Titanite 
  in 
  a 
  few 
  small 
  grains 
  was 
  noted 
  in 
  no. 
  11. 
  

  

  Reaction 
  or 
  corrosion 
  rims. 
  Reaction 
  or 
  corrosion 
  rims, 
  which 
  

   are 
  well 
  known 
  in 
  many 
  basic 
  rocks, 
  are 
  exhibited 
  in 
  a 
  truly 
  re- 
  

  

  