﻿Geology 
  and 
  Mineralogy. 
  427 
  

  

  The 
  author 
  does 
  not 
  believe, 
  to 
  any 
  great 
  extent, 
  in 
  the 
  

   hypothesis 
  of 
  differentiation, 
  to 
  account 
  for 
  the 
  origin 
  of 
  igneous 
  

   rocks. 
  He 
  thinks 
  rather 
  that 
  the 
  solution 
  of 
  this 
  problem 
  is 
  to 
  

   be 
  found 
  in 
  the 
  refusion 
  or 
  melting 
  down 
  on 
  a 
  large 
  scale 
  of 
  pre- 
  

   existent 
  rocks, 
  and 
  supports 
  his 
  view 
  by 
  what 
  he 
  has 
  observed 
  in 
  

   South 
  Africa. 
  It 
  would 
  be 
  beyond 
  the 
  limits 
  of 
  this 
  brief 
  notice 
  

   to 
  attempt 
  an 
  exposition 
  of 
  his 
  ideas 
  regarding 
  the 
  origin 
  and 
  

   mise 
  en 
  place 
  of 
  the 
  igneous 
  rocks, 
  but 
  petrographers, 
  while 
  they 
  

   may 
  not 
  agree 
  with 
  much 
  that 
  is 
  suggested 
  by 
  the 
  author, 
  will 
  

   nevertheless 
  find 
  the 
  work 
  of 
  interest 
  and 
  deserving 
  of 
  considera- 
  

   tion, 
  l. 
  v. 
  P. 
  

  

  6. 
  On 
  a 
  supposed 
  new 
  occurrence 
  of 
  Plattnerite 
  in 
  the 
  Coeur 
  

   d'Alene; 
  by 
  Ea.ul 
  V. 
  Sha^^ox 
  (communicated). 
  — 
  A 
  specimen 
  

   of 
  a 
  massive 
  mineral 
  apparently 
  corresponding 
  to 
  plattnerite 
  

   from 
  this 
  district 
  has 
  been 
  presented 
  to 
  me 
  by 
  Mr. 
  Henry 
  Savage 
  

   of 
  Kellogg, 
  Idaho. 
  The 
  locality 
  is 
  given 
  as 
  the 
  old 
  upper 
  workings 
  

   of 
  the 
  Mammoth 
  Mine 
  of 
  the 
  Federal 
  Co., 
  located 
  high 
  on 
  the 
  

   mountain 
  above 
  Mace, 
  where 
  Mr. 
  Savage 
  and 
  Leslie 
  Lamm 
  are 
  

   operating 
  a 
  lease. 
  Several 
  pounds 
  of 
  the 
  material 
  are 
  said 
  to 
  

   have 
  been 
  discarded 
  as 
  " 
  iron 
  " 
  and 
  buried 
  in 
  the 
  filling 
  of 
  the 
  

   worked-out 
  portion 
  of 
  the 
  stope, 
  until, 
  recognizing 
  the 
  great 
  

   weight 
  of 
  the 
  substance, 
  Mr. 
  Savage 
  brought 
  a 
  specimen 
  to 
  

   Kellogg 
  and 
  submitted 
  it 
  to 
  Mr. 
  Wm. 
  McM. 
  Huff 
  for 
  examina- 
  

   tion. 
  The 
  results 
  showed 
  a 
  large 
  proportion 
  of 
  lead 
  and 
  a 
  few 
  

   preliminary 
  blowpipe 
  tests 
  showed 
  that 
  the 
  lead 
  ore 
  was 
  not 
  one 
  

   of 
  the 
  more 
  common 
  oxidized 
  products 
  of 
  this 
  metal 
  and 
  it 
  was 
  

   provisionally 
  considered 
  plattnerite. 
  

  

  The 
  specimen 
  which 
  I 
  was 
  fortunate 
  enough 
  to 
  obtain 
  is 
  a 
  

   rough 
  nodule 
  covered 
  with 
  ocherous 
  limonite 
  except 
  where 
  frac- 
  

   tures 
  show 
  the 
  mineral 
  inside. 
  Some 
  well-bounded 
  mammillary 
  

   surfaces 
  are 
  present. 
  The 
  interior 
  of 
  the 
  nodule 
  consists 
  of 
  a 
  

   grayish 
  black 
  mineral 
  of 
  sub-metallic 
  luster 
  and 
  the 
  peculiar 
  

   greasy 
  look 
  of 
  lead 
  compounds. 
  In 
  appearance 
  the 
  mineral 
  is 
  

   entirely 
  similar 
  to 
  some 
  forms 
  of 
  compact 
  pyrolusite, 
  and 
  might 
  

   easily 
  be 
  mistaken 
  for 
  such 
  were 
  it 
  not 
  for 
  the 
  high 
  specific 
  grav- 
  

   ity 
  which, 
  judging 
  roughly 
  by 
  comparison, 
  must 
  be 
  7*5 
  or 
  8. 
  The 
  

   mineral 
  is 
  hard 
  for 
  a 
  lead 
  compound 
  ; 
  it 
  scratches 
  apatite 
  but 
  not 
  

   orthoclase 
  and 
  is 
  hence 
  near 
  5*5, 
  the 
  compared 
  hardness 
  given 
  for 
  

   the 
  originally 
  described 
  mineral 
  by 
  Yeates 
  and 
  Ayres. 
  Alone 
  on 
  

   charcoal 
  it 
  fuses' 
  at 
  a 
  low 
  heat 
  and 
  immediately 
  reduces 
  giving 
  

   a 
  large 
  lead 
  button. 
  No 
  oxide 
  coating 
  is 
  obtained 
  by 
  the 
  reduc- 
  

   tion, 
  but 
  only 
  upon 
  oxidizing 
  the 
  metallic 
  lead 
  obtained. 
  Heated 
  

   in 
  the 
  closed 
  and 
  open 
  tube 
  it 
  fuses 
  easily 
  to 
  a 
  brown 
  glass. 
  No 
  

   sublimate 
  was 
  obtained 
  by 
  heating 
  up 
  to 
  the 
  point 
  where 
  the 
  soft 
  

   glass 
  became 
  liquid 
  nor 
  was 
  any 
  moisture 
  given 
  off. 
  In 
  the 
  borax 
  

   bead 
  the 
  splinters 
  were 
  quickly 
  absorbed 
  and 
  formed 
  a 
  bead 
  

   which 
  in 
  both 
  flames 
  was 
  greenish 
  yellow 
  when 
  hot 
  and 
  clear 
  and 
  

   colorless 
  when 
  cold. 
  

  

  If 
  the 
  substance 
  is 
  really 
  plattnerite, 
  of 
  which 
  there 
  seems 
  little 
  

   doubt, 
  it 
  seems 
  desirable 
  to 
  put 
  on 
  record 
  this 
  second 
  definite 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Fourth 
  Series, 
  Vol. 
  XXXVI, 
  No. 
  214. 
  — 
  October, 
  1913. 
  

  

  28 
  

  

  