SOUTHWESTERN    NEVADA    AND    EASTERN    CALIFORNIA.  65 
a  continuation  of  the  Gold  Mountain  ridge  and  lie  south  of  the  Oriental  Wash  and  east  of 
Death  Valley.  Here  a  mass  of  post-Jurassic  biotite-granite  injects  a  highly  altered  series 
of  limestone  of  Cambrian  or  possibly  of  Silurian  age.  Contact  metamorphism  has 
developed  brown  garnet,  epidote,  quartz,  and  other  metamorphic  minerals.  The  granite 
contains  numerous  pyrite  crystals,  probably  original.  Rhyolitic  and  basaltic  rocks,  rem- 
nants of  eroded  Tertiary  lava  flows,  also  occur  in  the  vicinity. 
At  one  prospect  a  thin  quartz  vein  cuts  the  limestone.  Malachite,  azurite,  and  chryso- 
colla,  and  limonite-stained  chalcedonic  quartz  occur  in  irregular  patches  and  veinlets 
through  the  quartz.  Vugs  occur  in  the  secondary  minerals  and  the  azurite  and  malachite 
are  often  set  with  numerous  quartz  crystals.  A  little  chalcopyrite  is  embedded  in  the  oldest 
quartz,  and  cores  of  chalcopyrite  are  surrounded  by  the  other  copper  minerals.  A  vein  of 
malachite  1  inch  in  width  is  exposed  in  another  prospect,  apparently  replacing  the  limestone. 
The  general  resemblance  in  structural  relations  and  mineralogic  composition  of  these 
deposits  to  those  near  the  granite  of  Oak  Springs  is  worthy  of  note.  The  nearest  water  to 
these  prospects  is  Sand  Springs,  6  miles  away.  Fuel  could  be  obtained  from  Gold  Mountain, 
within  10  miles.     By  road  the  prospects  are  45  miles  from  the  railroad  terminus  at  Goldfield. 
NYE    COUNTY,  NEW 
Silverbow. — The  village  of  Silverbow  is  situated  in  the  canyon  of  Breens  Creek,  on  the 
west  side  of  the  Kawich  Range  and  about  42  miles  north  of  east  of  Goldfield.  The  principal 
prospects  are  within  3  miles  to  the  east,  northeast,  and  northwest  of  Silverbow.  The  first 
locations  were  made  in  November,  1904.  When  visited  by  the  writer  (July  20,  1905), 
Silverbow  was  the  supply  center  for  several  hundred  men  and  a  number  of  shallow  prospect 
holes  had  been  sunk. 
The  north  end  of  the  rugged  Kawich  Range  is,  with  unimportant  exceptions,  composed  of 
rhyolites  and  other  siliceous  eruptive  rocks.  The  ore  deposits  lie  in  rhyolite,  which  in  the 
vicinity  of  veins  is  either  kaolinized  to  a  soft  chalky  mass  or  silicified,  the  latter  alteration 
being  perhaps  more  common.  The  silicified  rhyolite  is  sometimes  flinty  in  texture  and  is 
very  resistant  to  erosion,  and  in  consequence  forms  prominent  minor  ridges  parallel  to  the 
veins.  In  the  kaolinized  facies  the  feldspar  phenocrysts  are  either  kaolinized  or  removed  in 
solution,  while  biotite,  if  present,  is  altered  to  a  silvery  micaceous  mineral.  Either  facies 
may  be  intensely  stained  red,  brown,  or  yellow  by  iron  salts. 
The  more  important  prospects  are  located  in  parallel  quartz  veins  or  lenses  which  widen, 
thin,  and  often  play  out,  forming  mineralized  bands  whose  strike  in  the  district  is  in  many 
cases  north  of  west.  The  individual  quartz  veins  vary  in  width  from  a  fraction  of  an  inch 
to  5  feet,  and  these  are  often  connected  by  minor  cross  veins.  While  in  many  cases  the 
quartz  was  deposited  along  pre-mineral  faults,  in  others  it  occurs  along  joints,  which  some- 
times form  intersecting  systems.  Quartz  likewise  often  fills  the  spaces  caused  by  brecci- 
ation  and  forms  in  solution  cavities  in  the  rhyolite.  The  quartz  is,  as  a  rule,  white  and 
translucent  or  colorless  and  transparent,  although  in  the  Blazier  tunnel  a  single  vein  of 
amethyst  was  noted.  Crystal-lined  vugs  are  common.  Crustification  is  often  beautifully 
developed,  fortification-agate  and  mammillary  forms  being  common. 
The  quartz  is  more  or  less  stained  by  iron  salts,  rarely  by  malachite.  In  the  quartz  specks 
of  stephanite,  ruby  silver,  silver  chloride,  and  probably  other  silver  ores  occur.  Of  these, 
silver  chloride  is  certainly  a  secondary  mineral,  and  to  a  limited  extent  is  disseminated  in  the 
country  rock.  Gold  occurs  free.  Silver  is  the  predominant  metal,  and  $1  in  gold  to  S3  in 
silver  is  perhaps  an  average  for  the  whole  camp,  although  in  some  prospects  the  silver  values 
are  twenty  times  those  of  gold.  The  ore  runs  from  $6  to  $250  per  ton,  while  higher  values 
are  reported.  Since  the  writer's  visit  strikes  in  which  gold  predominates  over  silver  have 
been  reported. 
In  other  prospects  values  occur  in  limonite  stringers  in  the  country  rock,  while  in  several 
prospects  a  greasy,  crushed  rhyolite  carries  gold  values. 
Bull.  285—06 5 
