﻿J. 
  B. 
  Umpleby, 
  etc. 
  — 
  Custerite 
  : 
  A 
  New 
  Mineral. 
  391 
  

  

  are 
  zeophyllite,* 
  cuspidinef 
  and 
  hillebrandite.;}: 
  The 
  relation- 
  

   ship 
  in 
  composition 
  can 
  be 
  best 
  shown 
  by 
  directly 
  comparing 
  

   their 
  analyses. 
  

  

  Comparison 
  of 
  Composition 
  of 
  Custerite 
  with 
  Related 
  Minerals. 
  

  

  

  Custerite 
  

  

  Zeophyllite 
  

  

  SiO, 
  

  

  32-17 
  

  

  38-84 
  

  

  CaO 
  

  

  55-11 
  

  

  44-32 
  

  

  H 
  2 
  0... 
  

  

  5-30 
  

  

  8-98 
  

  

  F 
  

  

  8-12 
  

  

  8-23 
  

  

  Etc 
  _.. 
  

  

  2-19 
  

  

  2-62 
  

  

  Deduct 
  

  

  102-89 
  

  

  102-99 
  

  

  = 
  F 
  

  

  — 
  3-42 
  

  

  — 
  3-47 
  

  

  

  99-47 
  

  

  99-52 
  

  

  Cuspidine 
  

   Franklin 
  

  

  Furnace 
  

  

  32-36 
  

   61-37 
  

  

  9*05 
  

   1-46 
  

  

  104-24 
  

   — 
  3-81 
  

  

  100-43 
  

  

  Vesuvius 
  

  

  32*80 
  

  

  61*12 
  

  

  none 
  

  

  9-88 
  

  

  0-42 
  

  

  104-22 
  

   — 
  3-98 
  

  

  100-24 
  

  

  Hille- 
  

   brandite 
  

  

  32-59 
  

  

  57-76 
  

  

  9-36 
  

  

  0-53 
  

  

  100-24 
  

  

  Zeophyllite 
  is 
  the 
  only 
  one 
  of 
  the 
  three 
  minerals 
  which 
  con- 
  

   tains 
  both 
  water 
  and 
  fluorine. 
  The 
  proportions 
  of 
  silica 
  and 
  

   lime 
  are 
  different 
  from 
  those 
  in 
  custerite, 
  though 
  structurally 
  

   its 
  formula 
  may 
  be 
  written 
  in 
  a 
  somewhat 
  similar 
  way. 
  The 
  

   mineral 
  is 
  described 
  as 
  rhombohedral, 
  the 
  crystals 
  being 
  com- 
  

   posed 
  of 
  a 
  uniaxial 
  center 
  surrounded 
  by 
  a 
  biaxial 
  border. 
  On 
  

   being 
  heated, 
  the 
  mineral 
  becomes 
  uniformly 
  and 
  permanently 
  

   uniaxial. 
  In 
  its 
  crystal 
  form 
  and 
  physical 
  and 
  optical 
  proper- 
  

   ties, 
  there 
  is 
  no 
  relation 
  between 
  zeophyllite 
  and 
  the 
  other 
  

   minerals 
  chemically 
  related 
  to 
  custerite. 
  In 
  its 
  paragenesis 
  it 
  

   is 
  also 
  totally 
  different 
  from 
  custerite, 
  being 
  a 
  zeolite-like 
  min- 
  

   eral 
  found 
  in 
  basalt 
  with 
  natrolite, 
  calcite, 
  apophyllite, 
  analcite, 
  

   etc. 
  A 
  specimen 
  of 
  zeophyllite 
  obtained 
  through 
  the 
  kindness 
  

   of 
  Dr. 
  Koechlin 
  of 
  the 
  Vienna 
  Hof-Museum 
  was 
  tested 
  for 
  

   its 
  alkaline 
  reaction 
  and 
  found 
  to 
  give 
  only 
  a 
  very 
  faint 
  pink 
  

   color 
  with 
  phenolphthaline. 
  

  

  The 
  dual 
  optical 
  character 
  of 
  zeophyllite 
  suggests 
  strongly 
  

   that 
  it 
  is 
  polymorphous. 
  Possibly, 
  the 
  uniaxial 
  compound 
  is 
  

   the 
  zeolite-like 
  mineral, 
  bearing 
  no 
  relation 
  to 
  custerite, 
  cuspi- 
  

  

  *Pelikan, 
  A., 
  Sitzber. 
  Akad. 
  Wien, 
  vol. 
  iii 
  (1), 
  p. 
  334, 
  1902. 
  Cornu, 
  F., 
  

   Min. 
  Petr. 
  Mitt., 
  vol. 
  xxiv, 
  p. 
  127, 
  1905. 
  

  

  f 
  Palache, 
  C, 
  this 
  Journal, 
  vol. 
  xxix, 
  p. 
  185, 
  1910. 
  Zambonini, 
  F., 
  Miner- 
  

   alogia 
  Vesuviana, 
  Att. 
  Accad. 
  Sci. 
  Napoli, 
  vol. 
  xiv, 
  No. 
  6, 
  p. 
  273, 
  1910. 
  

  

  % 
  Wright, 
  F. 
  E., 
  this 
  Journal 
  (4), 
  vol. 
  xxvi, 
  p. 
  551, 
  1908. 
  

  

  