﻿36 
  Edkins 
  — 
  Analyses 
  of 
  Astrophyllite 
  and 
  Tscheffkinite. 
  

  

  4-7 
  

  

  which 
  is 
  quite 
  close 
  to 
  R" 
  4 
  R' 
  4 
  Ti(Si0 
  4 
  ) 
  4 
  , 
  the 
  excess 
  of 
  the 
  R' 
  

   group 
  is 
  presumably 
  due 
  to 
  the 
  percentage 
  of 
  water 
  being 
  

   somewhat 
  too 
  large, 
  this 
  may 
  result 
  from 
  incipient 
  alteration 
  

   of 
  the 
  mineral, 
  which 
  may 
  also 
  be 
  the 
  cause 
  of 
  the 
  variation 
  

   in 
  color. 
  

  

  II. 
  Tscheffkinite. 
  

  

  A 
  fragment 
  of 
  this 
  rare 
  mineral 
  was 
  last 
  year 
  sent 
  to 
  the 
  

   National 
  Museum 
  by 
  Mr. 
  Horace 
  M. 
  Engle, 
  of 
  Roanoke, 
  Ya. 
  

   And 
  upon 
  its 
  identification 
  he 
  very 
  kindly 
  presented 
  all 
  at 
  his 
  

   disposal 
  for 
  the 
  purpose 
  of 
  investigation 
  ; 
  in 
  addition 
  to 
  some 
  

   small 
  fragments 
  there 
  was 
  one 
  large 
  mass, 
  which 
  before 
  break- 
  

   ing 
  weighed 
  over 
  three 
  and 
  one-half 
  kilograms, 
  most 
  of 
  it 
  

   now 
  being 
  in 
  the 
  museum 
  collection. 
  It 
  was 
  found 
  in 
  Bedford 
  

   Co., 
  Ya., 
  a 
  point 
  considerably 
  farther 
  south 
  than 
  the 
  locality 
  

   of 
  the 
  material 
  analyzed 
  by 
  Price.* 
  The 
  various 
  pieces 
  of 
  this 
  

   tscheffkinite 
  when 
  found 
  were 
  all 
  more 
  or 
  less 
  rounded 
  nodules, 
  

   with 
  a 
  superficial 
  brownish 
  yellow 
  ochreous 
  coating, 
  evidently 
  

   an 
  alteration 
  product, 
  which 
  at 
  some 
  later 
  date 
  may 
  be 
  made 
  

   the 
  subject 
  of 
  investigation 
  to 
  endeavor 
  to 
  determine 
  the 
  

   method 
  of 
  alteration. 
  The 
  beginning 
  of 
  this 
  alteration 
  w.is 
  

   also 
  seen 
  in 
  the 
  numerous 
  fissure 
  planes 
  developed 
  in 
  breaking 
  

   up 
  these 
  nodules. 
  Examination 
  of 
  a 
  fresh 
  surface 
  showed 
  a 
  

   distinctly 
  banded 
  structure 
  of 
  lustrous 
  black 
  and 
  dull 
  black 
  

   material, 
  the 
  bands 
  varying 
  from 
  mere 
  lines 
  to 
  over 
  five 
  mil- 
  

   limeters 
  in 
  width. 
  As 
  well 
  as 
  could 
  be 
  these 
  two 
  differently 
  

   appearing 
  substances 
  were 
  separated 
  and 
  each 
  analyzed 
  by 
  

   itself, 
  such 
  separation 
  however 
  was 
  only 
  approximate, 
  as 
  under 
  

   a 
  magnifying 
  glass 
  it 
  was 
  seen 
  that 
  each 
  band 
  contained 
  veins 
  

   of 
  the 
  other. 
  Analysis 
  I 
  is 
  that 
  of 
  the 
  lustrous 
  part, 
  and 
  II 
  

   that 
  of 
  the 
  dull. 
  

  

  Duplicate 
  determinations 
  confirmed 
  these 
  specific 
  gravities, 
  

   the 
  seemingly 
  more 
  altered 
  one 
  being 
  the 
  higher. 
  The 
  ac- 
  

   tion 
  of 
  acids 
  on 
  the 
  powdered 
  materials 
  shows 
  a 
  marked 
  

   difference, 
  the 
  lustrous 
  portion 
  being 
  completely 
  decomposed 
  

   in 
  a 
  few 
  minutes 
  by 
  warm 
  and 
  moderately 
  strong 
  hydrochloric, 
  

   sulphuric 
  or 
  nitric 
  acids, 
  while 
  an 
  hour 
  or 
  more 
  was 
  necessary 
  

   to 
  decompose 
  the 
  dull 
  portion 
  under 
  similar 
  conditions. 
  A 
  

   fire 
  assay 
  of 
  a 
  fragment 
  of 
  this 
  tscheffkinite 
  was 
  made 
  by 
  Mr. 
  

   E. 
  L. 
  Howard, 
  of 
  the 
  U. 
  S. 
  Geological 
  Survey 
  and 
  gave 
  0*74 
  

   oz. 
  of 
  silver 
  per 
  ton. 
  

  

  These 
  analyses 
  show 
  that 
  the 
  two 
  bands 
  are 
  practically 
  iden- 
  

   tical 
  in 
  composition, 
  the 
  dull 
  being 
  somewhat 
  more 
  hydrated. 
  

   The 
  molecular 
  ratios 
  seem 
  to 
  lead 
  to 
  no 
  definite 
  or 
  satisfactory 
  

  

  * 
  R. 
  C. 
  Price, 
  Am. 
  Chem. 
  Journal, 
  Jan., 
  1888. 
  

  

  