﻿340 
  Penjield 
  and 
  Warren 
  — 
  Minerals 
  from 
  FranTdin^ 
  N, 
  J, 
  

  

  far 
  it 
  has 
  been 
  observed 
  only 
  in 
  very 
  small, 
  lath-shaped 
  crys- 
  

   tals, 
  the 
  largest 
  being 
  not 
  over 
  0*5""" 
  in 
  length 
  and 
  O'lS"^" 
  in 
  

   diameter, 
  and 
  these 
  generally 
  are 
  so 
  intimately 
  associated 
  with 
  

   garnet, 
  axinite 
  and 
  phlogopite 
  that 
  it 
  was 
  for 
  a 
  long 
  time 
  diffi- 
  

   cult 
  to 
  secure 
  a 
  specimen 
  from 
  which 
  a 
  sufficient 
  quantity 
  of 
  

   the 
  pure 
  material 
  could 
  be 
  obtained 
  for 
  the 
  chemical 
  analysis. 
  

   The 
  accompanying 
  iigure 
  is 
  a 
  sketch 
  of 
  one 
  of 
  the 
  crystals 
  as 
  

   seen 
  under 
  the 
  microscope. 
  The 
  faces 
  are 
  striated 
  parallel 
  to 
  

   the 
  longer 
  axis 
  of 
  the 
  crystals, 
  and 
  they 
  round 
  into 
  one 
  another 
  

   owing 
  to 
  oscillatory 
  combinations. 
  The 
  terminal 
  faces, 
  neces- 
  

  

  sarily 
  very 
  small, 
  are 
  vicinal, 
  and 
  it 
  has 
  thus 
  far 
  been 
  impossi- 
  

   ble 
  to 
  find 
  any 
  crystal 
  from 
  which 
  satisfactory 
  measurements 
  

   of 
  the 
  interfacial 
  angles 
  could 
  be 
  obtained. 
  As 
  may 
  be 
  seen 
  

   from 
  the 
  figure 
  the 
  habit 
  of 
  the 
  crystals 
  is 
  like 
  that 
  of 
  epidote 
  ; 
  

   that 
  is, 
  the 
  prominent 
  faces 
  are 
  parallel 
  to 
  the 
  axis 
  of 
  symme- 
  

   try, 
  and 
  the 
  crystals 
  are 
  terminated 
  by 
  two 
  faces 
  correspond- 
  

   ing 
  to 
  the 
  form 
  n 
  (111) 
  of 
  epidote. 
  On 
  one 
  of 
  the 
  crystals 
  it 
  

   was 
  possible 
  to 
  obtain 
  approximate 
  measurements 
  with 
  the 
  

   Fuess 
  reflecting 
  goniometer 
  by 
  using 
  a 
  strong 
  illumination 
  

   of 
  the 
  signal 
  and 
  the 
  S 
  ocular. 
  The 
  'measurements, 
  given 
  in 
  

   the 
  accompanying 
  table, 
  although 
  not 
  sufficiently 
  accurate 
  for 
  

   establishing 
  an 
  axial 
  ratio, 
  indicate 
  that 
  the 
  forms 
  and 
  angles 
  of 
  

   hancockite 
  are 
  similar 
  to 
  those 
  of 
  epidote. 
  

  

  

  Hancockite, 
  

  

  

  

  Approximate 
  measurements. 
  

  

  Epidote. 
  

  

  C/se, 
  OOl^lOl 
  = 
  

  

  36° 
  15' 
  

  

  34° 
  43' 
  

  

  e/^a, 
  101^100 
  = 
  

  

  30 
  45 
  

  

  29 
  54 
  

  

  C^r, 
  OOlys.101 
  =:. 
  

  

  63 
  

  

  63 
  42 
  

  

  r/s«, 
  101/slOO 
  =: 
  

  

  55 
  30 
  

  

  51 
  41 
  

  

  ?^/v?^, 
  111 
  /sill 
  = 
  

  

  67 
  

  

  70 
  29 
  

  

  c^n,OQl/^l\l 
  — 
  

  

  77 
  

  

  75 
  11 
  

  

  , 
  Although 
  the 
  appearance 
  of 
  the 
  mineral 
  in 
  the 
  hand 
  speci- 
  

   men 
  varies 
  from 
  a 
  dark 
  to 
  a 
  light 
  brownish-red, 
  single 
  crystals, 
  

   as 
  seen 
  with 
  a 
  pocket 
  lens, 
  have 
  a 
  yellowish-brown 
  color. 
  Crys- 
  

   tals 
  like 
  fig. 
  1, 
  when 
  examined 
  with 
  the 
  polarizing 
  microscope, 
  

   exhibit 
  distinct 
  pleochroism, 
  yellowish-brown 
  for 
  vibrations 
  

   parallel 
  to 
  b, 
  which 
  corresponds 
  to 
  the 
  crystallographic 
  axis 
  b^ 
  

   and 
  somewhat 
  variable 
  for 
  vibrations 
  at 
  rio-ht 
  ano'les 
  to 
  this 
  

   direction, 
  being 
  delicate 
  rose 
  color 
  at 
  the 
  attached 
  end 
  and 
  

  

  