﻿Shannon 
  — 
  Anglesite 
  from 
  Idaho. 
  287 
  

  

  Aet. 
  XVIII. 
  — 
  Anglesite 
  from 
  The 
  Coeur 
  d' 
  Alene 
  Dis- 
  

   trict, 
  Idaho; 
  by 
  Eael 
  V. 
  Shannon. 
  

  

  Although 
  the 
  Coeur 
  d' 
  Alene 
  District 
  has 
  been 
  a 
  pro- 
  

   lific 
  source 
  for 
  fine 
  crystallized 
  lead 
  minerals, 
  anglesite 
  

   has 
  always, 
  heretofore, 
  been 
  a 
  rarity 
  in 
  the 
  ores. 
  In 
  

   this 
  connection, 
  it 
  may 
  be 
  well 
  to 
  quote 
  Ransome 
  1 
  who, 
  

   after 
  an 
  examination 
  of 
  all 
  of 
  the 
  mines 
  of 
  the 
  District 
  

   in 
  1904-5, 
  writes 
  as 
  follows 
  : 
  

  

  "Anglesite, 
  the 
  sulphate 
  of 
  lead, 
  has 
  not 
  been 
  recognized 
  in 
  

   the 
  District, 
  That 
  the 
  galena 
  should 
  for 
  the 
  most 
  part 
  change 
  

   to 
  cernssite 
  is 
  easily 
  understood 
  in 
  light 
  of 
  the 
  fact 
  that 
  the 
  

   accompanying 
  conversion 
  of 
  the 
  siderite 
  gangue 
  to 
  limonite 
  sets 
  

   free 
  an 
  abundant 
  carbonic 
  anhydride 
  which 
  probably 
  goes 
  into 
  

   solution, 
  partly 
  free 
  and 
  partly 
  combined 
  with 
  calcium, 
  magne- 
  

   sium, 
  and 
  where 
  oxygen 
  is 
  deficient, 
  with 
  some 
  iron, 
  in 
  the 
  form 
  

   of 
  bicarbonates. 
  The 
  direct 
  oxidation 
  of 
  galena 
  should 
  give 
  the 
  

   lead 
  sulphate, 
  anglesite, 
  and 
  in 
  districts 
  where 
  the 
  oxidizing 
  

   waters 
  are 
  deficient 
  in 
  carbonates 
  or 
  rich 
  in 
  sulphuric 
  acid 
  or 
  

   sulphates, 
  as 
  for 
  example 
  the 
  San 
  Juan 
  district 
  in 
  Colorado, 
  

   anglesite 
  is 
  a 
  common 
  alteration 
  product 
  of 
  galena. 
  Penrose 
  

   states 
  that 
  the 
  oxidation 
  of 
  the 
  lead 
  sulphide 
  to 
  sulphate 
  is 
  a 
  

   necessary 
  step 
  in 
  the 
  formation 
  of 
  cernssite 
  from 
  galena 
  and 
  

   Emmons 
  found 
  at 
  Leadville 
  that 
  chemical 
  tests 
  showed 
  the 
  occur- 
  

   rence 
  of 
  a 
  thin 
  crust 
  of 
  anglesite 
  between 
  the 
  galena 
  and 
  cerussite. 
  

   In 
  the 
  Coeur 
  d' 
  Alene 
  District, 
  however, 
  no 
  anglesite 
  has 
  been 
  

   detected, 
  the 
  snlphide 
  and 
  carbonate 
  being 
  directly 
  in 
  contact, 
  

   The 
  galena, 
  however, 
  does 
  not 
  pass 
  into 
  compact 
  cerussite 
  but 
  

   is 
  replaced 
  by 
  loose 
  bunches 
  of 
  crystals, 
  many 
  of 
  which 
  are 
  of 
  

   large 
  size. 
  As 
  a 
  rule, 
  masses 
  of 
  galena 
  in 
  process 
  of 
  oxidation 
  

   show 
  irregularly 
  etched 
  or 
  corroded 
  cavities 
  upon 
  the 
  walls 
  of 
  

   which 
  are 
  planted 
  crystals 
  of 
  cernssite. 
  It 
  is 
  clear 
  that 
  in 
  the 
  

   formation 
  of 
  these 
  large 
  free-growing 
  crystals 
  considerable 
  

   molecular 
  or 
  ionic 
  migration 
  mnst 
  have 
  taken 
  place, 
  and 
  it 
  is 
  

   quite 
  possible 
  that 
  under 
  such 
  circumstances 
  and 
  in 
  the 
  presence 
  

   of 
  abundant 
  carbonates 
  in 
  solution 
  the 
  anglesite 
  may 
  have 
  formed 
  

   and 
  been 
  immediately 
  changed 
  to 
  cerussite, 
  the 
  process 
  being 
  

   such 
  that 
  no 
  visible 
  quantity 
  of 
  anglesite 
  could 
  accumulate. 
  Even 
  

   where 
  the 
  ore 
  contains 
  bunches 
  of 
  almost 
  completely 
  oxidized 
  

   pyrite, 
  as 
  in 
  the 
  Last 
  Chance 
  mine, 
  and 
  where 
  sulphates 
  or 
  sul- 
  

   phuric 
  acid 
  were 
  presumably 
  more 
  than 
  usually 
  abundant, 
  the 
  

   galena, 
  directly 
  in 
  contact 
  with 
  the 
  porous 
  limonite 
  resulting 
  

   from 
  the 
  oxidation 
  of 
  the 
  pyrite, 
  has 
  altered 
  to 
  cernssite 
  with 
  

   no 
  visible 
  anglesite. 
  

  

  1 
  Kansome, 
  F. 
  L., 
  Geology 
  & 
  Ore 
  Deposits 
  of 
  The 
  Coeur 
  d 
  ' 
  Alene 
  Mining 
  

   District, 
  Idaho. 
  U. 
  S. 
  G. 
  S., 
  Prof. 
  Paper 
  62, 
  p. 
  132. 
  

  

  