SOUTHWESTERN"    NEVADA    AND    EASTERN    CALIFORNIA.  59 
the  gulch  to  the  northwest  of  the  mountain.  Active  work  ceased  in  1887,  but  at  present 
a  number  of  prospectors  are  reopening  old  properties  and  locating  new  claims.  The  dist  rict 
product,  estimated  at  $500,000,  was  freighted  in  wagons  to  Belmont,  65  miles  away.  At 
present  only  a  few  shallow  prospect  holes  and  the  dumps  of  the  old  mines  are  accessible 
for  examination. 
The  Montezuma  hills  are  a  rugged  spur  of  the  Silver  Peak  Range,  the  highest  poinl  being 
Montezuma  Peak.  The  mineralized  area  lies  to  the  west  of  this  mountain  in  Cambrian 
sedimentary  rocks.  Compact,  fine-grained,  black  limestone,  intimately  cut  by  quartz 
and  calcite  veinlets,  predominates  over  light-colored  quar.tzites  and  green  shales.  The 
Cambrian  is  cut  by  dioritc-porphyry  and  quartz-latite  dikes.  The  folding  of  the  sedimentary 
rocks  is  rather  gentle,  although  local  buckling  of  the  strata  is  observed.  The  productive 
area  is  surrounded  by  nonmineralized  Tertiary  lavas  and  sediments. 
In  the  old  mines  the  chief  gangue  is  quartz,  with  rarely  u  little  calcite  and  kaolinitic 
material  associated.  Vugs  filled  with  quartz  crystals  occur  in  the  quartz.  The  ores  at 
the  surface  are  cerussite,  malachite,  azurite,  and  limonite,  and  associated  with  these  and 
replacing  them  in  depth  are  galena,  chalcocite,  and  pyrite.  The  values  are  largely  in  silver, 
the  gold  values  being  uniformly  low.  Chlorobromides  of  silver  are  reported,  but  were 
not  seen. 
A  prospect  hole  exposes  a  quartz  vein  with  a  diorite-porphyry  dike  as  hanging  wall  and 
limestone  as  foot  wall.  Chalcopyrite  is  the  original  sulphide,  and  malachite  with  less 
limonite,  azurite,  and  a  little  native  copper  are  the  secondary  ores.  The  native  copper 
forms  knife-edges  in  cracks  and  small  nodules  in  the  vein.  Malachite  partially  replacing 
limestone  was  noted  at  a  number  of  other  places. 
Copper  and  lead  sulphides  with  quartz  fill  open  fissures  in  limestone.  Some,  probably 
all,  of  the  deposition  followed  the  dike  injection,  of  probably  pre-Tertiary  age.  Later 
the  veins  were  crushed  and  surface  waters  altered  the  sulphides  to  carbonates,  oxides, 
native  metals,  and  probably  minerals  of  the  haloid  series.  That  the  chemical  breakdown 
of  the  sulphides  is  continuing  is  indicated  by  the  water  flowing  from  an  abandoned  tunnel 
southwest  of  the  mill;  this  deposits  considerable  limonite  and  is  so  charged  with  ferrous 
sulphate  that  animals  will  scarcely  drink  it. 
In  several  of  the  older  mines  and  prospects,  water,  some  of  which  is  suitable  for  domestic 
purposes,  was  encountered  at  a  depth  of  30  feet.  The  mines  will  probably  require  pumps, 
but  abundant  fuel  surrounds  them.  Goldfield,  the  railroad  terminus,  is  9  miles  distant, 
the  road  being  fairly  good. 
Cuprite. — The  copper  prospects  of  the  Cuprite  mining  district  lie  in  a  belt  1  mile  wide 
which  extends  from  a  point  17  miles  south  of  Goldfield  westward  to  Mount  Jackson.  The 
district  is  a  new  one,  the  first  locations  having  been  made  early  in  1905.  The  mines  lie 
from  2  to  9  miles  west  of  the  stage  and  automobile  road  between  Goldfield  and  Bullfrog. 
The  low  hills  in  which  the  mines  lie  are  composed  of  Cambrian  sedimentary  rocks  and 
flows  of  later  eruptives.  The  Cambrian  rocks  are,  as  usual,  predominantly  limestones 
of  black  color  and  rather  fine  grain,  and  subordinately  green  shale,  often  paper  thin,  with 
semischistose  facies.  The  limestone  and  shales  are  gently  folded,  the  predominant  dip 
being  westward.  Minor  normal  faults,  in  some  instances  intimately  connected  with  the 
ore  deposits,  are  common.  The  Cambrian  at  Cuprite,  as  at  Lida,  is  cut  by  dikes  of 
diorite-porphyry.  Here  also  these  appear  to  have  no  intimate  connection  with  the  ore 
deposits.  To  the  north  of  the  copper  belt  rhyolitic  rocks  cover  considerable  areas.  Resid- 
ual areas  of  later  basalt  flows  of  no  economic  importance  cover  both  the  Cambrian  and 
rhyolite  at  a  number  of  localities. 
The  properties  of  the  Goldfield-Midway-Bullfrog  Mining  Company  and  the  Tri-Metallic 
Mining  Company  may  be  taken  as  types  of  the  copper  properties  of  the  Cuprite  mining 
district. 
The  Copper  Bell  shaft  of  the  first-named  company  is  located  on  the  side  of  a  gentle 
valley  in  Cambrian  sedimentary  rocks  and  is  now  85  feet  deep.  The  shaft  is  being  sunk 
to  encounter  a  vein  which  strikes  N.  60°  E.  and  dips  from  80°-85°  NW.     This  vein  has 
