﻿38 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  still 
  unaltered. 
  As 
  the 
  process 
  goes 
  on, 
  new 
  fissures 
  are 
  cleft 
  in 
  con- 
  

   sequence 
  of 
  the 
  increase 
  of 
  volume 
  associated 
  with 
  the 
  alteration 
  

   and 
  thus 
  render 
  possible 
  the 
  constant 
  increase 
  of 
  the 
  new 
  structures 
  

   until 
  the 
  olivine 
  is 
  completely 
  transformed. 
  " 
  

  

  "In 
  the 
  alteration 
  of 
  hornblende 
  and 
  actinolite 
  into 
  serpentine 
  the 
  

   cleavage 
  planes 
  of 
  amphibole 
  and 
  their 
  oblique 
  separations 
  are 
  very 
  

   clearly 
  brought 
  out 
  in 
  the 
  arrangement 
  of 
  the 
  serpentine 
  bundles. 
  

   Between 
  crossed 
  nicols 
  the 
  lines 
  of 
  parallel 
  fibres 
  dififerentiate 
  them- 
  

   selves 
  in 
  lively 
  colors 
  from 
  the 
  dark 
  ground 
  of 
  the 
  confusedly 
  fibrous 
  

   field, 
  now 
  running 
  parallel 
  to 
  one 
  another 
  now 
  intersecting 
  one 
  

   another 
  at 
  an 
  angle 
  of 
  124° 
  to 
  125°, 
  or 
  forming 
  rhombic 
  figures 
  with 
  

   other 
  angles 
  and 
  rectangles. 
  There 
  results 
  in 
  this 
  way 
  a 
  structure 
  

   which 
  is 
  characteristic 
  in 
  the 
  highest 
  degree 
  and 
  which 
  Wiegand 
  

   designated 
  as 
  lattice 
  or 
  window 
  structure. 
  " 
  

  

  " 
  Other 
  serpentines, 
  which, 
  microscopically, 
  occasionally 
  show 
  a 
  

   schistose 
  structure, 
  under 
  the 
  microscope 
  appear 
  to 
  consist 
  of 
  foliated 
  

   masses 
  which 
  cross 
  each 
  other 
  at 
  right 
  angles 
  and 
  so 
  show 
  a 
  netted 
  

   structure. 
  " 
  " 
  These 
  serpentines 
  appear 
  to 
  have 
  resulted 
  from 
  the 
  

   alteration 
  of 
  monoclinic 
  pyroxenes. 
  " 
  

  

  From 
  the 
  alteration 
  of 
  the 
  rhombic 
  pyroxenes 
  is 
  produced 
  both 
  

   serpentine 
  and 
  bastite. 
  

  

  According 
  to 
  Tschermak 
  the 
  alteration 
  of 
  olivine 
  into 
  serpentinti 
  

   may 
  be 
  expressed 
  as 
  follows 
  : 
  — 
  

  

  Olivine 
  consists 
  of 
  Mg2Si04 
  and 
  Fe2Si04 
  combined 
  in 
  varying 
  

   proportions. 
  

  

  2 
  (Mg2Si04) 
  + 
  CO2 
  + 
  2B.20=2U20, 
  3MgO, 
  2Si02 
  + 
  MgCOa. 
  

  

  5 
  (Fe2Si04) 
  + 
  O 
  + 
  6H20=2Fe304 
  + 
  2Fe203, 
  3H2O 
  + 
  5Si02. 
  

  

  A 
  small 
  portion 
  of 
  the 
  MgO 
  in 
  the 
  serpentine 
  is 
  replaced 
  by 
  FeO. 
  

  

  SERPENTINE 
  LOCALITIES 
  NEAR 
  NEW 
  YORK. 
  

  

  The 
  serpentines 
  in 
  the 
  vicinity 
  of 
  New 
  York 
  City 
  are 
  of 
  two 
  gen- 
  

   eral 
  classes 
  : 
  

  

  A. 
  Serpentine 
  masses 
  of 
  large 
  area. 
  / 
  

  

  B. 
  Local 
  developments 
  of 
  serpentine 
  in 
  crystalline 
  magnesian 
  

   limestones. 
  

  

  