GOLD   AND   SILVER. 
In  addition  to  the  papers  here  included,  which  represent  the  results  of  recent  work  hy 
the  Survey  in  important  precious-metal  mining  districts,  other  reports  bearing  incidentally 
on  the  subject  of  gold  and  silver  will  be  found  under  the  head  of  "Copper,"  on  pages  93 
to  145,  and  "Lead  and  zinc,"  on  pages  166  to  170. 
ORE  DEPOSITS  OF  BEAR  CREEK,  NEAR  SILVERTON, 
COLO. 
By  W.  H.  Emmons. 
General  description. — The  Bear  Creek  mining  camp  is  in  the  northeast  corner  of  the 
Needle  Mountains  quadrangle,  near  the  head  of  Bear  Creek,  a  tributary  of  the  Rio  Grande 
near  its  source.  It  includes  also  a  group  of  claims  at  the  extreme  head  of  Elk  Creek,  to 
the  west  just  over  the  continental  divide.  It  is  about  17  miles  from  Silverton;  9  miles 
of  this  distance  is  over  a  wagon  road  by  way  of  Howardsville,  up  Cunningham  Gulch,  and 
the  remainder  is  over  a  good  pack  trail.  The  district  may  also  be  reached  by  wagon  road 
from  Creede,  a  distance  of  about  40  miles,  and  in  the  summer  of  1905  a  trail  was  being 
constructed  from  Elk  Park,  on  the  Denver  and  Rio  Grande  Railroad,  only  about  9  miles 
away.  The  country  is  extremely  rugged  and  much  of  it  is  above  timber  line.  The  region 
was  prospected  as  early  as  1878.  The  Gold  Bug  mine  was  among  the  first  located  and 
was  sold  to  Kansas  City  parties,  who,  it  is  said,  took  out  about  $50,000  worth  of  very  rich 
ore.  The  Good  Hope  and  Sylvanite  have  also  produced  considerable  amounts,  and  ship- 
ments have  been  made  from  a  number  of  other  properties.  The  entire  district  has  pro- 
duced about  $200,000,  chiefly  in  high-grade  tellurium  ores.  Nearly  all  of  this  was  packed 
out  by  mule  trains. 
When  the  camp  was  visited  in  August,  1905,  the  most  largely  developed  mines  had 
been  idle  for  years  and  the  portals  of  several  of  their  tunnels  were  blocked  with  snow  and 
ice,  so  that  entrance  to  all  the  workings  was  impossible.  A  number  of  smaller  properties 
were  being  developed,  and  the  data  gained  from  the  examination  of  these  and  from  the 
surface  workings  of  the  larger  mines  appear  to  be  in  full  accord  with  those  reported  for 
the  workings  then  inaccessible. 
Geology. — The  geology  of  the  Needle  Mountains  quadrangle  is  treated  in  folio  131  of  the 
United  States  Geological  Survey,  by  Whitman  Cross  and  Ernest  Howe,  and  their  geolog- 
ical map  was  used  as  a  basis  for  this  report. 
The  Bear  Creek  deposits  are  located  in  an  area  of  pre-Cambrian  schists,  slates,  and 
quartzites,  partly  covered  by  San  Juan  andesite  tuffs  and  by  later  flows.  The  Archean 
schists,  which  are  the  oldest  rocks,  have  a  laminated,  streaked  appearance  and  are  com- 
posed mainly  of  mica,  quartz,  and  feldspar.  Scams  or  veins  of  quartz,  often  as  mu<  h  as 
3  or  4  inches  wide,  are  common.  These  are  known  to  prospectors  as  "bull  quartz"  or 
"barren  quartz,"  and  are  carefully  avoided. 
The  slates  and  the  quartzites  belong  to  the  Uncompahgre  formation  and,  though 
pre-Cambrian,  are  younger  than  the  Archean  schists,  upon  which  they  rest  unconform- 
ably,     They  are  the  metamorphosed  products  of  shale  and  sandstone.     Certain  portions 
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