﻿126 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  all 
  coming 
  from 
  the 
  dumps. 
  The 
  study 
  of 
  the 
  exposures 
  has 
  led 
  

   us 
  to 
  the 
  belief 
  that 
  the 
  balls 
  may 
  have 
  had 
  a 
  glassy 
  crust 
  origi- 
  

   nally, 
  and 
  that 
  this 
  has 
  been 
  sheared 
  free 
  from 
  them 
  by 
  subsequent 
  

   movements. 
  At 
  present 
  all 
  glassy 
  material 
  is 
  between 
  the 
  balls 
  

   and 
  most 
  of 
  it 
  has 
  been 
  much 
  crushed 
  by 
  shearing. 
  

  

  Thin 
  sections 
  from 
  the 
  rock 
  of 
  the 
  balls 
  show 
  a 
  network 
  of 
  

   minute 
  feldspar 
  laths 
  set 
  in 
  what 
  is 
  certainly 
  in 
  some 
  cases, 
  and 
  

   probably 
  in 
  all, 
  a 
  glass 
  base. 
  In 
  the 
  finer 
  grained 
  rock 
  from 
  the 
  

   margins 
  of 
  the 
  balls 
  the 
  laths 
  have 
  a 
  prominent 
  radial 
  or 
  spherulitic 
  

   arrangement. 
  The 
  somewhat 
  coarser 
  rock 
  from 
  the 
  centers 
  has 
  

   the 
  same 
  arrangement, 
  but 
  less 
  prominently. 
  The 
  laths 
  are 
  minute 
  

   and 
  not 
  greatly 
  twinned. 
  In 
  the 
  coarser 
  varieties 
  extinctions 
  up 
  

   to 
  20 
  ° 
  are 
  shown 
  and 
  the 
  feldspar 
  is 
  probably 
  andesine-labradorite. 
  

  

  In 
  none 
  of 
  the 
  slides 
  is 
  there 
  any 
  determinable 
  pyroxene, 
  nor 
  

   anything 
  which 
  especially 
  suggests 
  altered 
  pyroxene. 
  In 
  the 
  finer 
  

   grained 
  rock 
  it 
  is 
  quite 
  certain 
  that 
  no 
  pyroxene 
  ever 
  crystallized 
  

   out; 
  in 
  the 
  coarser 
  rock 
  some 
  may 
  perhaps 
  have 
  done 
  so, 
  as 
  there 
  

   are 
  small 
  scattered 
  patches 
  of 
  calcite 
  and 
  possibly 
  alteration 
  

   products 
  between 
  the 
  feldspars 
  which 
  may 
  have 
  resulted 
  from 
  

   pyroxene 
  alteration. 
  But 
  we 
  regard 
  it 
  as 
  most 
  probable 
  that 
  the 
  

   stage 
  of 
  crystallization 
  of 
  pyroxene 
  had 
  not 
  been 
  reached 
  in 
  any 
  

   of 
  the 
  rock 
  at 
  the 
  time 
  of 
  solidification. 
  

  

  All 
  the 
  slides 
  show 
  occasional, 
  sharply 
  bounded 
  areas 
  which 
  

   have 
  the 
  outlines 
  of 
  porphyritic 
  crystals. 
  A 
  number 
  of 
  these 
  seem 
  

   quite 
  certainly 
  original 
  olivines; 
  the 
  outer 
  form 
  and 
  the 
  angles 
  

   are 
  precisely 
  those 
  of 
  that 
  mineral. 
  This 
  has 
  led 
  to 
  the 
  belief 
  

   that 
  all 
  are 
  probably 
  original 
  crystals 
  of 
  olivine. 
  They 
  show 
  three 
  

   different 
  types 
  of 
  alteration. 
  

  

  In 
  type 
  1 
  the 
  mineral 
  is 
  entirely 
  gone 
  to 
  a 
  fine, 
  light 
  greenish, 
  

   feebly 
  polarizing 
  aggregate, 
  which 
  seems 
  unquestionable 
  chlorite. 
  

   A 
  few 
  individuals 
  show 
  traces 
  of 
  a 
  mesh 
  structure 
  which 
  suggests 
  

   serpentine, 
  but 
  this 
  is 
  by 
  no 
  means 
  the 
  rule. 
  This 
  is 
  the 
  more 
  

   usual 
  alteration. 
  

  

  In 
  type 
  2 
  the 
  original 
  mineral 
  is 
  entirely 
  replaced 
  by 
  calcite, 
  

   fairly 
  coarsely 
  crystallized, 
  or 
  else 
  by 
  calcite 
  and 
  quartz. 
  This 
  is 
  

   the 
  same 
  mineral 
  combination 
  found 
  in 
  the 
  amygdules. 
  

  

  Type 
  3 
  is 
  the 
  least 
  common 
  and 
  seems 
  to 
  be 
  a 
  further 
  stage 
  of 
  

   the 
  alteration 
  shown 
  in 
  type 
  1. 
  The 
  material 
  is 
  either 
  brown 
  and 
  

   wholly 
  opaque, 
  or 
  else 
  this 
  with 
  the 
  addition 
  of 
  tiny, 
  colorless 
  

   patches 
  which 
  show 
  faint 
  double 
  refraction. 
  

  

  