﻿184 
  Foote 
  and 
  Bradley 
  — 
  Solid 
  Solution 
  in 
  Minerals. 
  

  

  instance, 
  is 
  not 
  of 
  necessity 
  H 
  4 
  Si0 
  4 
  or 
  H 
  2 
  Si0 
  3 
  , 
  but 
  homogen- 
  

   eous 
  material 
  containing 
  more 
  or 
  less 
  water 
  may 
  equally 
  well 
  

   be 
  obtained, 
  depending 
  on 
  the 
  method 
  of 
  preparation. 
  

  

  Looked 
  at 
  in 
  this 
  way, 
  the 
  composition 
  of 
  chrysocolla 
  is 
  very 
  

   simple. 
  The 
  mineral 
  is 
  not 
  a 
  chemical 
  compound 
  and 
  no 
  for- 
  

   mula 
  should 
  be 
  assigned, 
  but 
  a 
  solid 
  solution 
  of 
  copper 
  oxide, 
  

   silica 
  and 
  water 
  as 
  essential 
  components, 
  whose 
  composition 
  

   depends 
  on 
  the 
  conditions 
  of 
  formation. 
  This 
  is, 
  of 
  course, 
  

   not 
  in 
  accord 
  with 
  the 
  view 
  that 
  every 
  mineral 
  is 
  a 
  definite 
  

   chemical 
  compound, 
  but 
  it 
  accounts 
  for 
  the 
  facts 
  regarding 
  

   composition, 
  in 
  a 
  way 
  that 
  no 
  definite 
  formula 
  can 
  do. 
  The 
  

   possibility 
  of 
  there 
  being 
  chemical 
  combination 
  between 
  the 
  

   components 
  of 
  the 
  solid 
  solution 
  is 
  not 
  excluded, 
  just 
  as 
  a 
  salt 
  

   dissolved 
  in 
  water 
  may 
  be 
  chemically 
  combined 
  with 
  the 
  latter, 
  

   but 
  we 
  have 
  no 
  means, 
  any 
  more 
  than 
  with 
  other 
  types 
  of 
  

   solution, 
  of 
  determining 
  the 
  nature 
  of 
  this 
  combination. 
  

  

  This 
  tentative 
  view 
  of 
  the 
  composition 
  of 
  chrysocolla, 
  if 
  

   generally 
  adopted, 
  should 
  logically 
  be 
  extended 
  to 
  a 
  large 
  

   number 
  of 
  the 
  minerals 
  which 
  commonly 
  occur 
  in 
  the 
  amor- 
  

   phous 
  condition. 
  The 
  fact 
  that 
  some 
  of 
  them 
  occur 
  occasion- 
  

   ally 
  in 
  a 
  more 
  or 
  less 
  crystalline 
  condition 
  appears 
  to 
  be 
  no 
  

   objection 
  to 
  assuming 
  solid 
  solution. 
  Poorly 
  developed 
  crys- 
  

   tals 
  are 
  rather 
  evidence 
  of 
  this. 
  For 
  instance, 
  when 
  ammonium 
  

   chloride 
  is 
  pure, 
  it 
  is 
  well 
  crystallized. 
  When 
  it 
  forms 
  solid 
  

   solutions 
  with 
  a 
  variety 
  of 
  other 
  chlorides 
  of 
  different 
  types, 
  

   such 
  as 
  nickel 
  chloride, 
  the 
  crystals 
  are 
  distorted 
  and 
  imperfect. 
  

  

  A 
  calculation 
  of 
  the 
  ratios 
  of 
  144 
  analyses 
  of 
  the 
  various 
  

   ferric 
  hydrate 
  minerals, 
  given 
  in 
  Dana's 
  Mineralogy 
  and 
  

   Hintze's 
  Handbuch, 
  indicates 
  that 
  with 
  these 
  minerals, 
  as 
  with 
  

   chrysocolla, 
  there 
  are 
  no 
  definite 
  compounds 
  in 
  the 
  series, 
  

   but 
  that 
  all 
  may 
  be 
  considered 
  as 
  solid 
  solutions 
  of 
  water 
  

   either 
  in 
  ferric 
  oxide 
  or 
  in 
  some, 
  as 
  yet 
  undetermined, 
  lower 
  

   hydrate. 
  

  

  Chemical 
  and 
  Mineralogical 
  Laboratories 
  

  

  of 
  the 
  Sheffield 
  Scientific 
  School 
  of 
  Yale 
  University, 
  

  

  New 
  Haven, 
  Conn., 
  May, 
  1913. 
  

  

  