48  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260; 
edly  slaty,  and  its  ores  are  chiefly  chaleopyrite  or  hornite,  with  copper 
carbonates  near  the  surface. 
The  rocks  along  the  contact  are  generally  much  sheared  and  the 
shear  zone  is  apparently  somewhat  richer  than  those  on  either  side. 
No  characteristic  contact  minerals  were  observed  to  suggest  that  ores 
in  this  case  were  originally  contact  deposits  modified  after  the  devel- 
opment of  the  slaty  cleavage. 
The  Five  Bear  mine,  in  the  slates,  is  much  like  the  Grass,  but 
the  Green  Ledge,  Pilot,  and  others  in  the  porphyry  have  small 
veins  of  quartz,  with  bornite  and  some  chalcocite.  The  veins  are 
generally  less  than  5  inches  in  thickness. 
The  Cosmopolitan  mine  is  on  the  contact  of  the  granodiorite  with 
the  Triassic  limestones  and  shales.  The  ore  is  bornite  and  chaleopy- 
rite, forming  solid  bodies  up  to  15  feet  in  thickness,  with  greater 
dimensions  in  the  plane  of  contact,  along  which  other  smaller  bodies  of 
the  same  ore  occur.  On  the  surface  the  contact  is  marked  by  masses 
of  garnet  and  epidote  which  were  not  seen  beneath,  but  in  the  Dun- 
can mine  the  garnet  and  epidote  are  associated  with  the  ore. 
The  Bluebell  mine  is  in  the  Triassic  limestone,  near  the  contact, 
and  from  one  of  its  shafts  some  tons  of  carbonate  of  copper  have  been 
brought  up  in  connection  with  cave  breccia,  suggesting  a  secondary 
deposit  within  the  limestone.  A  small  vein  of  barite  occurs  in  altered 
andesites  at  the  Indian  Valley  silver  mine  and  locally  contains 
traces  of  copper  ore. 
Near  the  northwest  end  of  the  Genesee  belt  is  the  Superior  mine, 
in  which  the  gangue  of  the  bornite  is  a  green  fibrous  mineral  like 
actinolite.  A  number  of  parallel  vertical  veins  of  this  mineral  are 
well  exposed  in  the  open  cut  and  contain  disseminated  particles  and 
nodules  of  bornite.  The  larger  ore  bodies  are  free  from  gangue. 
The  wall  rock  is  the  same  on  both  sides,  and  the  veins  are  sharply 
defined. 
AURIFEROUS  GRAVELS. 
Development. — In  the  Taylorsville  region  modern  stream  beds 
have  been  mined  in  Lights  Canyon  and  on  Indian  Creek,  above 
Flournoys,  as  well  as  below  Arlington  bridge.  The  total  yield  of 
these  modern  gravels  is  in  the  neighborhood  of  $10,000  annually. 
About  the  head  of  Lights  Creek,  Mountain  Meadows,  and  Moon- 
light, high  gravels  have  been  mined  irregularly  in  a  small  way  for 
over  twenty  years,  and  the  total  yield,  according  to  a  conservative 
estimate,  is  nearly  $500,000. 
Geology  of  the  high  gravels. — In  the  Taylorsville  region  the  high 
gravels  are  well  illustrated  by  those  at  Peale's  and  Taylor's  diggings, 
which  lie  on  the  flat  crests  of  divides  over  1,000  feet  above  the  streams 
on  either  side.    They  belong  to  the  moderate  slopes  of  the  gentle  relief 
