﻿2-00 
  

  

  2*00 
  

  

  2-00 
  

  

  3*78 
  

  

  4-01 
  

  

  4-01 
  

  

  1-10 
  

  

  1-24 
  

  

  2-14 
  H 
  2 
  or 
  

  

  1-59 
  

  

  1-79 
  

  

  4-27 
  F 
  

  

  390 
  J. 
  B. 
  Umpleby, 
  etc. 
  — 
  Custerite 
  : 
  A 
  New 
  Mineral. 
  

  

  Interpretation 
  of 
  Ratios 
  of 
  Average 
  Custerite 
  Analysis. 
  

  

  Combining 
  Deducting 
  Combining 
  water 
  

   Ratios 
  CaO 
  + 
  MgO 
  diopside 
  and 
  fluorine 
  

  

  Si0 
  2 
  -536 
  

  

  CaO 
  '984 
  

  

  MgO 
  -030 
  

  

  H 
  2 
  '294 
  

  

  F 
  .._ 
  '427 
  

  

  The 
  formula 
  derived 
  "for 
  custerite 
  is: 
  Ca 
  2 
  SiHF0 
  4 
  with 
  some 
  

   of 
  the 
  fluorine 
  replaced 
  by 
  water 
  (hydroxyl). 
  The 
  composi- 
  

   tion 
  may 
  also 
  be 
  expressed 
  as 
  a 
  mixture 
  of 
  the 
  two 
  compounds 
  : 
  

   2Si0 
  2 
  .4Ca0.2H 
  2 
  and 
  2Si0 
  2 
  .4Ca0.4F, 
  with 
  the 
  first 
  one 
  

   slightly 
  in 
  excess. 
  The 
  relation 
  of 
  the 
  fluorine 
  to 
  water 
  

   (hydroxyl) 
  can 
  be 
  much 
  better 
  shown 
  in 
  the 
  empirical 
  formula, 
  

   according 
  to 
  which 
  the 
  ratios 
  reduce 
  to 
  Ca 
  4 
  Si 
  2 
  6 
  (OH,F) 
  4 
  with 
  

   the 
  ratio 
  of 
  hydroxyl 
  (Oil) 
  to 
  fluorine 
  (F) 
  as 
  2*48:1-79, 
  or 
  

   nearly 
  4:3. 
  

  

  ]STo 
  water 
  was 
  given 
  off 
  on 
  heating 
  custerite 
  to 
  110°, 
  indicat- 
  

   ing 
  that 
  the 
  water 
  is 
  an 
  inherent 
  part 
  of 
  the 
  mineral. 
  The 
  

   temperature 
  at 
  which 
  the 
  water 
  does 
  go 
  off 
  was 
  not 
  determined 
  

   but 
  the 
  observation 
  was 
  repeatedly 
  made 
  that 
  the 
  phosphores- 
  

   cence 
  phenomenon 
  displayed 
  itself 
  and 
  was 
  destroyed 
  by 
  heat 
  

   before 
  the 
  water 
  was 
  given 
  off. 
  Some 
  powdered 
  custerite, 
  

   placed 
  in 
  a 
  watchglass 
  with 
  several 
  cubic 
  centimeters 
  of 
  water, 
  

   immediately 
  gives 
  a 
  deep 
  red 
  color 
  with 
  a 
  few 
  drops 
  of 
  phenol- 
  

   phthaline. 
  This 
  reaction 
  was 
  described 
  by 
  Clarke,* 
  and 
  he 
  has 
  

   suggested 
  that 
  it 
  is 
  indicative 
  of 
  the 
  presence 
  of 
  the 
  univalent 
  

   group 
  — 
  CaOH. 
  As 
  the 
  ratio 
  of 
  OH 
  to 
  F 
  is 
  approximately 
  

   1 
  : 
  1, 
  the 
  formula 
  of 
  custerite 
  may 
  be 
  structurally 
  interpreted 
  

   as 
  a 
  metasilicate, 
  as 
  follows 
  : 
  

  

  The 
  ratios 
  of 
  hydroxyl 
  (OH) 
  to 
  fluorine 
  (F) 
  being 
  not 
  exactly 
  

   1 
  : 
  1 
  but 
  more 
  nearly 
  4 
  : 
  3, 
  custerite 
  may 
  be 
  more 
  accurately 
  

   considered 
  as 
  an 
  isomorphous 
  mixture 
  of 
  the 
  following 
  com- 
  

   pounds, 
  in 
  the 
  ratio 
  indicated. 
  

  

  *[«o.<as>[«o.<ss] 
  

  

  Relation 
  to 
  other 
  minerals. 
  — 
  There 
  are 
  only 
  three 
  minerals 
  

   known 
  to 
  which 
  custerite 
  is 
  related 
  in 
  composition. 
  These 
  

  

  * 
  Clarke, 
  F. 
  W., 
  Contributions 
  to 
  chemistry 
  and 
  mineralogy 
  from 
  the 
  

   Laboratory 
  of 
  the 
  United 
  States 
  Geological 
  Survey: 
  Bull. 
  U. 
  S. 
  G. 
  S., 
  No. 
  

   167, 
  p. 
  156,. 
  1900. 
  

  

  