HAHNS    PEAK    GOLD    FIELD,    COLORADO.  33 
This  passes  through  the  following  strata: 
Section  at  Southern  Cross  tunnel,  Ilahns  Peak,  Colorado. 
Feet. 
Porphyry  talus  slope 75 
Solid  white  porphyry 50 
Light-colored  plastic  kaolin  clay L25 
An  apparent  fault  breccia,  ending  in  a  black  clay  shale 28 
Solid  white  porphyry 322 
GOO 
Mr.  Richard  Paulson  is  still  at  work  on  this  tunnel.  This  development  is  important  as 
showing  that  zones  of  solfataric  action  exist  within  the  mass  of  white  porphyry.  Some 
mineralization  has  taken  place  along  the  breccia  zone,  and  a  few  little  streaks  of  galena 
and  silver  have  been  found.  The  plastic  kaolin  clay  is  interpreted  as  the  product  of  decom- 
position in  place  of  the  white  porphyry,  and  the  breccia  of  angular  fragmen  s  as  marking 
a  zone  of  faulting.  The  porphyry  beyond  the  breccia  to  the  breast  of  the  tunnel  is  consid- 
erably altered,  as  evidenced  by  the  kaolinization  of  the  feldspars. 
The  Oro-Cache  tunnel  is  on  the  east  side  of  the  peak.  It  is  said  to  have  been  driven 
600  feet  into  the  white  porphyry  in  search  of  the  gold  veins.  It  is  now  abandoned  and 
inaccessible. 
The  Ely- Young  tunnel,  on  the  west  side  of  the  peak,  passed  through  a  porphyry  talus 
slope  for  about  150  feet,  then  through  the  black  shale  of  the  Benton  to  the  Dakota  quartz- 
ite,  about  400  feet  in  all,  in  the  expectation  of  finding  ore  between  these  rocks.  At  the  time 
of  visit  the  tunnel  had  passed  into  the  quartzite,  but  no  mineral  had  been  found. 
On  Farwell  Mountain  is  a  group  of  prospects  entirely  distinct  from  those  that  have  been 
described  from  the  rest  of  this  field.  About  thirty  claims  are  located  here,  on  most  of 
which  assessment  work  only  has  been  done.  A  few  of  the  developments  have  been  carried 
in  from  100  to  200  feet.  The  ore  indications  seen  were  of  copper,  mostly  impregnations 
of  a  coarse  granite  and  pegmatite,  and  of  horneblende-gneiss  and  diorite,  usually  near  the 
contact  of  these  two  groups  of  rocks.  There  are  also  quartz  veins  carrying  mineral,  but 
such  as  were  seen  were  in  the  form  of  stringers,  with  no  evidence  as  yet  of  strong  fracture 
zones.  The  minerals  were  mainly  the  alteration  products  malachite  and  azurite,  with 
some  chalcopyrite,  and  possibly  bornite  and  chalcocite.  These  are  said  to  have  assayed 
values  in  gold  and  silver.     No  workable  ore  bodies  have  yet  been  discovered." 
CONCLUSION. 
Interest  in  this  field  is  revived  with  the  expected  advent  of  the  Denver,  Northwestern 
and  Pacific  Railroad.  Nearer  railroad  facilities  may  render  feasible  projects  which  are 
not  so  under  present  conditions.  In  the  placer  grounds  the  deposits  that  would  pay  under 
the  methods  of  washing  hitherto  employed  are  mostly  worked  out,  but  they  may  yet  be 
worked  to  a  profit  by  hydraulicking  or  by  dredging.  The  difficulty  in  hydraulicking 
in  a  great  part  of  the  field  is  the  lack  of  grade  for  the  disposal  of  tailings.  Dredging  has 
not  yet  been  tried,  though  the  position  of  the  gravels,  the  softness  of  the  bed  rock,  and 
an  ample  water  supply  are  all  favorable  to  this  method  of  treatment. 
With  regard  to  the  lode  prospects  the  work  already  done  shows  that  there  lias  been  min- 
eralization within  the  mass  of  the  porphyry  of  Hahns  Peak,  but  as  yet  the  character  of 
the  deposits,  whether  simple  impregnation  of  the  country  rock  or  actual  lode  deposits,  has 
not  been  satisfactorily  determined.  Ore  is  also  said  to  have  been  found  in  the  Minnie  D., 
following  bedding  planes  in  the  sedimentary  beds  surrounding  the  porphyry  body,  but 
such  indications  do  not  offer  much  hope  for  permanent  deposits  unless  they  should  be 
found  in  the  underlying  limestone.     This  limestone,  however,  was  not  found  at  the  surface. 
a  For  a  more  complete  description  of  the  deposits  and  associated  country  rocks  of  similar  character, 
see  Spencer,  A.  C,  The  copper  deposits  of  the  Encampment  district,  Wyoming:  Prof.  Paper  U.S.  Geol 
Survey  No.  25,  1904. 
Bull.  285—06 3 
