COPPEE    DEPOSITS    OF    HABTVILLE    UPLIFT,    WYOMING.  95 
The  copper  deposits  of  the  Hartville  uplift  are  in  the  form  of  (1) 
ssure  veins,  (2)  lenticular  or  globular  masses  of  ore  outcropping  at 
tie  surface  and  pinching  out  at  slight  depths,  and  (3)  blanket  or 
edded  deposits  at  the  base  of  the  Guernsey  formation.  It  is  admit- 
>d  that  development  on  the  supposed  fissure  veins  has  not  advanced 
africiently  to  determine  their  character  beyond  all  doubt. 
Malachite,  chrysoeolla,  and  chalcocite  are  much  the  most  impor- 
int  ores.  Of  less  common  occurrence  are  tennantite  (?),  native  cop- 
er, azurite,  bornite,  covellite,  cuprite, a  and  chalcopyrite.  Closely 
ssociated  with  the  normal  green  chrysoeolla,  and  evidently  contem- 
oraneous  with  it,  is  a  soft  dark-brown  substance.  W.  T.  Schaller 
)und  this  to  contain  iron,  copper,  silica,  and  water,  and  it  is  proba- 
ly  chrysoeolla  with  considerable  iron  as  an  impurity.  A  yellow ish- 
reen  mineral  fills  fractures  at  several  prospects.  This  is,  according 
3  W.  F.  Hillebrand,  a  copper  arsenate.     Chalcocite  in  particular  as 
rule  carries  some  silver,  and  native  silver  occurs  at  the  Silver  Cliff 
line.  Gold  values  are  reported  from  iron-stained  schist  closely 
ssociated  with  the  copper  ores  in  several  places.  The  gangue  min- 
rals,  in  the  main  of  later  origin,  include  quartz,  calcite,  chalcedony, 
alenite,  and  barite. 
Copper  ores  occur  in  tne  pre-Cambrian  rocks  and  in  the  Guernsey 
filiation.  No  ore  body  has  yet  been  found  in  the  Hartville  fornia- 
ion  or  in  the  rocks  overlying  it.  A  possible  exception  is  the  pres- 
nce  of  slight  malachite  stains  on  blocks  of  Hartville  sandstone  in 
tie  talus  overlying  a  copper  deposit  in  Guernsey  limestone  in  the 
enter  of  the  NE.  \  sec,  36,  T.  27  N.,  R.  66  W.  This  malachite 
tain  is,  however,  superficial  and  was  probably  deposited  after  the 
lock  became  a  part  of  the  talus.  In  consequence,  in  prospecting 
3r  copper,  work  should  be  confined  to  the  area  delineated  on  the 
eologic  map  in  the  Hartville  folio6  as  being  underlain  by  either 
re-Cambrian  or  Guernsey  formations. 
The  more  important  copper  deposits  were  probably  deposited  by 
escending  waters  and  have  no  apparent  connection  with  igneous  rocks 
or,  except  in  one  place,  with  fault  planes.  The  Guernsey  formation, 
r  some  other  which  originally  overlay  it  and  which  prior  to  the  depo- 
ition  of  the  Hartville  formation  was  removed  by  erosion,  was  probably 
he  original  source  of  the  ore  of  the  larger  deposits.  The  copper  was 
•robably  included  as  a  chemical  or  mechanical  impurity  in  the  Guern- 
ey  formation.  Such  a  view  necessitates  the  former  existence  of  p  re- 
carboniferous  copper  deposits  in  the  area  from  which  the  Guernsey 
ormation  was  derived.  Possible  examples  of  such  deposits  are 
[escribed  as  fissure  veins  in  the  following  section. 
a  Mineral  Resources  U.  S.,  1882,  U.  S.  Geol.  Survey,  1883,  p.  758. 
b  Geologic  Atlas  U.  S.,  folio  91,  U.  S.  Geol.  Survey,  1903. 
Bull.  315—07 7 
