COPPER    MINES    OF    THE    UNITED    STATES NEW    MEXICO.        117 
the  northwestern  border  of  the  field  an  intrusion  of  granite  occurs  cutting  the  monzonite. 
The  mineral-bearing  porphyry  is  a  white  siliceous  rock,  with  a  brown  weathered  surface.  In 
places  it  is  so  silicified  that  it  forms  hard  masses  which  stand  out  in  relief  above  the  more 
gentle  slopes  of  softer,  leached  rock. 
The  ore  bodies  are  of  enormous  extent.  That  of  the  Eureka  mine  is  70  by  800  feet, 
and  has  been  developed  to  a  depth  of  100  feet.  That  of  the  Ruth  mine  has  a  width  of  50 
to  250  feet,  is  developed  for  400  to  900  feet  in  length,  and  has  a  known  vertical  thickness 
of  250  feet.  According  to  Channing,  from  whose  report  on  the  Nevada  Consolidated  Cop- 
per Mining  Company's  properties  these  notes  are  taken,  the  rock  is  leached  for  50  to  100 
feet  down,  carrying  not  over  one-half  of  1  per  cent  of  copper.  Below  this  the  ore  is  white 
and  soft,  and  consists  of  decomposed  porphyry  carrying  minute  seams  of  pyrite  and  copper 
glance,  with  some  quartz.  This  is  typical  "disseminated"  ore,  exactly  analogous  to  the 
ores  of  Morenci  and  Bingham.  At  the  Ruth  mine  there  is  a  640-foot  inclined  shaft,  having 
an  angle  of  41  °,  equal  to  420  feet  vertical.  Levels  are  driven  at  200,  300,  500,  and  6.50  feet  on 
the  incline,  and  the  ground  is  blocked  out  by  200-foot  crosscuts.  The  ore  has  a  content 
of  2.6  per  cent  of  copper  at  the  Ruth  mine  and  of  2.2  per  cent  of  copper  at  the  Eureka  mine, 
with  40  cents  per  ton  in  gold.  A  large  concentrating  plant  has  already  been  planned,  and 
with  the  completion  of  the  railroad  now  being  built  by  the  company  the  property  will  have 
an  estimated  output  of  3,000  tons  a  day.  It  is  expected  that  a  saving  will  be  made  of  77 
to  79  per  cent  of  the  values  of  the  ore.  These  properties  are  in  the  eastern  or  central 
portion  of  the  belt.  The  western  portion  of  the  quartz-monzonite  area  is  owned  by  the 
Giroux  Copper  Mining  Company. 
The  quartz-monzonite  mass  is  surrounded  by  contact-metamorphic  limestones  and 
shales,  in  which  there  are  pockets  of  ore,  but  up  to  the  present  time  no  large  ore  bodies 
have  been  found  in  such  rocks. 
NEW  MEXICO. 
Copper  mining  in  New  Mexico  during  1905  has  not  shown  the  same  marked  improvement 
in  condition  as  in  Arizona.  The  Territory  contains  a  dozen  or  more  areas  of  igneous  rock 
surrounded  by  borders  of  limestone  which  has  been  altered  by  contact  metamorphism 
and  impregnated  by  copper  ores.  Various  attempts  have  been  made  to  work  these  low- 
grade  ores,  notably  in  the  San  Pedro  Mountains,  but  thus  far  without  marked  success. 
There  seems  no  question  as  to  the  abundance  of  low-grade  garnetiferous  ore  at  all  these 
localities,  but  the  future  utilization  of  these  ores  is  a  metallurgical  problem.  The  exten- 
sion of  railroad  lines  in  1904  has  altered  conditions  materially,  and  with  the  assurance  of 
cheaper  coke  the  possibility  of  successful  reduction  seems  more  hopeful.  The  Santa  Rita 
mines  continue  to  produce  the  largest  amount  of  ore. 
The  copper  output  of  New  Mexico  for  19C5  is  estimated  at  3,500,000  pounds,  nearly  all 
from  Grant  County.     The  returns  for  1904  a  show  the  following  production  by  counties: 
Production  of  copper  in  New  Mexico,  1904,  ^y  counties. 
County. 
Quantity. 
Value. 
County. 
Quantity. 
Value. 
Donna  Ana... 
Pounds. 
40,000 
4,  428, 508 
16,000 
14,400 
846 
24,900 
$5,200 
575,706 
2,080 
1,872 
110 
3,237 
Pounds. 
2,  308 
10,700 
425, 508 
3,000 
8300 
Grant 
Sierra 
2,171 
Luna 
55, 310 
Otero 
Taos 
390 
Rio  Arriba 
Total.. 
4, 972, 170 
646, 382 
San  Miguel 
a  Lindgren,  Waldemar,  Production  of  gold  and  silver  in  1904:  Mineral  Resources  U.  S.  for  1904,  U.  S. 
Geol.  Survey,  1905. 
