﻿392 
  J. 
  B. 
  Umpleby, 
  etc. 
  — 
  Custerite: 
  A 
  New 
  Mineral. 
  

  

  dene 
  or 
  lrillebrandite. 
  The 
  biaxial 
  compound, 
  not 
  found 
  as 
  

   such 
  in 
  nature, 
  may 
  possibly 
  represent 
  a 
  compound 
  similar 
  in 
  

   properties 
  to 
  custerite, 
  cuspid 
  ine 
  and 
  hillebrandite. 
  Its 
  for- 
  

   mula, 
  Ca 
  4 
  Si 
  3 
  H 
  4 
  F 
  2 
  O 
  n 
  , 
  can 
  be 
  written 
  as 
  that 
  of 
  custerite 
  plus 
  

   one 
  part 
  of 
  metasilicic 
  acid, 
  thus 
  : 
  Ca 
  4 
  Si 
  2 
  H 
  2 
  F 
  2 
  8 
  (custerite) 
  + 
  

   H 
  2 
  Si0 
  3 
  , 
  but 
  what 
  significance, 
  if 
  any, 
  is 
  to 
  be 
  attached 
  to 
  this 
  

   fact 
  is 
  not 
  known. 
  The 
  formula 
  of 
  zeophyllite 
  can 
  be 
  inter- 
  

   preted 
  structurally 
  in 
  a 
  way 
  analogous 
  to 
  that 
  of 
  custerite, 
  

  

  Si 
  ° 
  3 
  C 
  +2H 
  a 
  O 
  

   CaF-SiO> 
  Ca 
  

  

  which 
  would 
  explain 
  the 
  fact 
  that 
  zeophyllite 
  does 
  not 
  give 
  a 
  

   strong 
  alkaline 
  reaction 
  with 
  phenolphthaline 
  but 
  seems 
  incon- 
  

   sistent 
  with 
  the 
  fact 
  that 
  less 
  than 
  one 
  per 
  cent 
  of 
  the 
  water 
  is 
  

   given 
  off 
  at 
  110°. 
  Other 
  structural 
  interpretations 
  are, 
  of 
  

   course, 
  possible. 
  

  

  Cuspidine, 
  found 
  originally 
  at 
  Vesuvius, 
  has 
  recently 
  been 
  

   described 
  from 
  Franklin 
  Furnace 
  by 
  Palache.* 
  At 
  Vesuvius 
  

   cuspidine 
  was 
  found 
  as 
  well- 
  developed 
  crystals 
  in 
  druses 
  asso- 
  

   ciated 
  with 
  augite, 
  hornblende, 
  biotite, 
  garnet, 
  sarcolite, 
  

   davyne, 
  and 
  calcite 
  (derived 
  from 
  altered 
  cuspidine). 
  Granu- 
  

   lar 
  aggregates 
  — 
  resembling 
  a 
  fine-grained 
  diabase 
  — 
  of 
  cuspi- 
  

   dine 
  with 
  augite 
  and 
  biotite 
  were 
  also 
  noted. 
  Attention 
  may 
  

   also 
  be 
  called 
  to 
  the 
  " 
  cuspidine-like 
  mineral" 
  found 
  f 
  with 
  

   green 
  magnesium 
  mica 
  and 
  white 
  sodalite, 
  and 
  occurring 
  in 
  

   rhombic 
  prisms, 
  apparently 
  different 
  from 
  cuspidine. 
  The 
  

   composition 
  of 
  this 
  material 
  is 
  not 
  known, 
  though 
  ZamboniniJ 
  

   considers 
  it 
  identical 
  with 
  humite. 
  

  

  The 
  density 
  of 
  the 
  Franklin 
  Furnace 
  cuspidine 
  is 
  given 
  as 
  

   2*965 
  — 
  2*989 
  and 
  that 
  of 
  Vesuvius, 
  as 
  determined 
  by 
  Zam- 
  

   bonini, 
  as 
  2*962 
  ; 
  average 
  value 
  2*97. 
  The 
  formula 
  derived 
  

   by 
  Zambonini, 
  namely, 
  Ca 
  2 
  (CaF) 
  2 
  Si 
  2 
  7 
  , 
  is 
  in 
  perfect 
  accord 
  

   with 
  his 
  own 
  analysis 
  and 
  with 
  Warren's 
  analysis 
  of 
  the 
  Frank- 
  

   lin 
  Furnace 
  material. 
  It 
  may 
  be 
  noted 
  that 
  the 
  presence 
  of 
  

   only 
  0*57 
  per 
  cent 
  of 
  water 
  (not 
  determined 
  according 
  to 
  War- 
  

   ren's 
  analysis) 
  in 
  the 
  Franklin 
  Furnace 
  mineral 
  woulfl 
  suffice 
  

   to 
  bring 
  the 
  ratio 
  of 
  [F 
  + 
  (OH)] 
  : 
  Si0 
  2 
  to 
  1*00 
  instead 
  of 
  

   1*00 
  : 
  0*88 
  as 
  calculated 
  from 
  his 
  analysis. 
  Structurally 
  the 
  

   formula 
  of 
  cuspidine 
  can 
  be 
  interpreted 
  as 
  : 
  

  

  Ca^^ 
  U 
  *<CaF 
  

  

  which 
  does 
  not 
  show 
  ,any 
  direct 
  relation 
  to 
  that 
  of 
  custerite. 
  

  

  *Loc. 
  cit. 
  

  

  f 
  Kath 
  von 
  G., 
  Zs. 
  Kryst., 
  vol. 
  viii, 
  p. 
  45, 
  1884. 
  

  

  :}: 
  Zambonini, 
  Appendice 
  alia 
  Mineralogia 
  Vesuviana 
  ; 
  Att. 
  Accad. 
  Sci., 
  

   Napoli, 
  vol. 
  xii, 
  p. 
  44, 
  1912. 
  

  

  