COPPER    DEPOSITS    OF    HAKTVILLE    UPLIFT,    WYOMING.  101 
of  malachite.  George  Botsford,  of  Sunrise,  reports  that  he  has 
observed  barite  crystals  covering  the  copper-  ores.  During  the  depo- 
sition of  these  ores  there  was  probably  some  slight  recrystallization 
of  hematite,  since  between  fractures  containing  copper  minerals  the 
hematite  is  softer  and  of  slightly  coarser  grain  than  that  farther  from 
the  copper. 
Two  thin  sections  of  copper  ore  in  hematite  were  examined  under 
the  microscope.  In  each ,  malachite  and  chrysocolla  till  fractures  most 
intricately  cutting  the  hematite,  and  in  each  the  copper  minerals  partly 
replace  hematite. 
Field  evidence  in  the  Hartville  uplift  appears  to  show  that  hema- 
tite has  been  an  important  precipitant  of  copper.  In  addition  to  the 
phenomena  at  the  Sunrise  mine,  the  copper  is  intimately  associated 
with  an  older,  heavily  hematized  gangue  in  the  pre-Cambrian  lime- 
stones, and  the  bedded  deposits  at  the  base  of  the  Guernsey  formation 
are  confined  largely  to  heavily  hematized  portions  of  the  sandstone. 
The  association  of  copper  ores  and  hematite  is  not  extraordinary, 
but  deposits  in  which  hematite  is  the  country  rock  end  is  older  than 
the  copper  ore  are  unusual.  At  the  Soudan a  and  Chandler6  mines,  on 
the  Vermilion  Range  in  Minnesota,  native  copper  and  various  car- 
bonates and  oxides  secondary  to  it  occur  in  fracture  zones  in  iron 
ore.  Hobbs  refers  the  precipitation  of  the  copper  to  the  oxidation  of 
ferrous  iron  compounds.  Haworthc  reports  films  of  native  copper 
in  fractures  in  "  Red  Beds"  at  Enid,  Okla.,  which  are  rich  in  hematite. 
He  believes  that  the  soluble  salts  of  copper  were  reduced  to  oxides  by 
the  hematite  and  that  the  ferrous  sulphate  which  formed,  in  the  pres- 
ence of  free  sulphuric  acid,  reduced  the  copper  oxides  to  the  native 
state.  At  the  Sunrise  mine  ferrous  salts  might  have  been  formed 
from  hematite  itself  and  by  their  oxidation  precipitated  the  copper 
minerals. 
In  the  Sunrise  mine  lenticular  or  pear-shaped  masses  of  copper  ore 
were  deposited  not  only  after  the  iron  ores  had  been  formed,  but  also 
after  they  had  been  fractured,  the  copper  deposition  having  occurred 
in  post-Guernsey  time.  The  distinct  termination  of  the  ore  with 
depth  may  indicate  that  it  was  deposited  by  descending  waters,  and 
since  copper  ore  extends  upward  into  the  Guernsey  formation  that 
formation  was  presumably  the  original  source. 
The  old  Village  Belle  copper  mine,  now  a  part  of  the  Sunrise  mine, 
appears  to  have  been  of  similar  character,  although  native  copper  is 
said  to  have  been  rather  common. 
oEby,  J.  II.,  and  Berkey,  C  P.,  Proc.  Lake  Superior  Min.  Inst.,  vol.  4,  1890,  pp.  69-79.  Winchell, 
N.  II.,  Minnesota  Geol.  and  Nat.  Hist.  Survey,  vol.  5.  1900,  p.  885.  Clements,  .1.  M.,  Mon.  U.  S.  Geol. 
Survey,  vol.  45,  1903,  pp.  113,  189.     Hobbs,  W.  II.,  Am.  Geologist,  vol.  36,  1905,  p.  185. 
b Clements,  J.  M.,  Mon.  U.  S.  Geol.  Survey,  vol.  45,  1903,  p.  184. 
ellaworth,  E.,  Bull.  Geol.  Soc.  America,  vol.  12,  1900,  pp.  2-4. 
