NORTHERN  IDAHO  AND  NORTHWESTERN  MONTANA.      49 
The  Great  Northwestern  property  is  situated  on  the  southwestern  slope  of  the  mountain. 
The  country  rock  is  grayish  siliceous  shale,  probably  of  the  Prichard  formation,  which  is  cut 
by  a  large  diabase  dike  trending  northwest  and  southeast.  A  fracture  zone  parallel  to  and 
lying  within  this  dike  forms  the  vein.  It  is  filled  with  white  quartz,  calcite,  and  iron-stained 
breccia,  is  from  2  to  6  feet  wide,  and  carries  galena,  some  iron  pyrite,  marcasite,  sideritc, 
sphalerite,  and  a  few  crystals  of  chalcopyrite.  The  ore  is  said  to  carry  from  18  to  50  ounces 
of  silver  per  ton  and  seems  to  occur  in  irregular  bunches.  The  vein  appears  to  be  richer 
where  it  is  cut  by  a  porphyry  dike  of  later  origin.  About  60  tons  of  ore  are  on  the  dump 
awaiting  the  construction  of  a  wagon  road  to  Troy,  12  miles  distant. 
The  Iron  Cap  property  adjoins  the  Great  Northwestern  and  seems  to  be  on  the  same  lead, 
which  here  cuts  typical  Prichard  slate.  It  has  been  opened  up  by  a  shallow  open  cut, 
exposing  a  large  amount  of  iron  capping  and  crushed  vein  material.  Some  pieces  of  galena 
are  found  throughout  the  less  weathered  parts. 
FUTURE    PROSPECTS. 
Though  comparatively  young,  the  Troy  district  shows  considerable  promise.  The  veins 
seem  to  be  strong  and  development  work  may  show  ore  bodies  of  considerable  extent.  In 
spite  of  the  fact  that  some  of  the  ores  carry  zinc,  wisely  directed  operations  should  produce 
some  paying  mines. 
SYLVANITE. 
Location. — Sylvanite  is  situated  in  the  Loop  Mountains  on  Yaak  River,  about  20  miles 
north  of  the  point  where  it  unites  with  the  Kootenai. 
Mines  and  properties. — The  Keystone  and  Goldflint,  situated  on  the  same  lead,  are  the  two 
principal  properties  in  the  district.  The  country  rock  is  Creston  quartzite.  In  being  folded 
to  its  present  form  certain  hard  beds  have  slipped  over  the  softer  beds.  Between  two  such 
folded  beds  lies  the  vein,  which  has  a  filling  of  white  quartz  and  iron-stained  crushed  rock. 
The  extent  of  the  workings  would  indicate  that  the  mine  had  produced  considerable  free- 
milling  gold  ore.  This  ore  was  concentrated  in  a  10-stamp  mill.  The  property  is  now  idle, 
owing,  it  is  reported,  to  litigation.  Base  ore  which  could  not  be  treated  by  the  free-milling 
process,  may,  however,  have  been  found  with  depth. 
SNOWSHOE  MINE. 
General  statement — The  Snowshoe  mine,  owned  by  the  Rustler  Mining  and  Milling  Com- 
pany of  Pittsburg,  comprises  three  patented  claims,  the  Snowshoe,  Rustler,  and  Porcupine. 
Information  regarding  the  output,  values,  etc.,  of  the  mine  was  courteously  afforded  by  the 
manager. 
Location.— The  Snowshoe  mine  is  situated  in  the  most  precipitous  and  rugged  part  of  the 
Cabinet  Range.     It  is  at  the  head  of  Libby  Creek  and  just  across  the  divide  from  Bull  Lake. 
A  good  wagon  road  down  Libby  Creek  connects  the  mine  with  the  Northern  Pacific  at 
Libby,  about  22  miles  to  the  north.  Several  four  and  six  horse  teams  haul  the  ore  out  and 
bring  in  the  supplies  over  this  road. 
Geology. — The  Snowshoe  vein  occupies  the  fissure  of  a  large,  clean-broken  fault.  The 
country  rock  on  the  east  side  of  the  fault  is  a  grayish-green  to  dark-gray  massive  shale  of  the 
Burke  formation,  and  on  the  west  side  a  calcareous  shale  of  the  Wallace  formation.  This 
shows  that  a  throw  of  several  thousand  feet  has  occurred.  Owing,  however,  to  the  fact  that 
the  fissure  is  here  almost  perpendicular,  there  has  been  a  minimum  of  friction  and  very  little 
gouge  has  been  formed. 
The  vein  is  clearly  defined,  has  almost  perpendicular  walls,  and  trends  north  and  south. 
Another  smaller  vein  lies  about  75  feet  east  of  the  main  lead  and  almost  parallel  to  it.  The 
filling  material  is  principally  white  quartz  and  crushed  rock,  with  a  few  inches  of  shiny  black 
talcose  parting  on  the  east  and  a  little  greenish-blue  gouge  on  the  west  wall. 
Development  work  has  opened  up  300  or  400  feet  of  depth  on  the  vein,  showing  lenticular 
masses  of  galena  and  an  average  width  of  about  7  feet. 
Bull.  285—06 4 
