toiN.]  LEAD    AND    ZINC    RESOURCES    OF    UNITED    STATES.  263 
tent  of  100,000  tons  of  metal  in  this  export  ore.  On  this  basis  the 
minimum  figures  for  the  total  production  of  the  United  States  would 
be  as  below. 
Estimated  total  production  of  zinc  in  the  United  States. 
Short  tons. 
Spelter    2,225,000 
Zinc  content  of  oxide  made  since  1880 533,000 
Zinc  content  of  ore  exports  since  181)7 100,  000 
Total   2,858,000 
ORES  OF  THE  MISSISSIPPI  VALLEY. 
JOPLIN  DISTRICT. 
The  geology  and  the  ore  deposits  of  this  district  have  been  discussed 
in  a  preliminary  way  in  several  survey  publications  noted  in  the 
accompanying  bibliography.  The  Joplin  district  includes  an  ill-de- 
fined area  of  approximately  1,200  square  miles,  lying  mainly  in  south- 
western Missouri,  but  extending  also  into  Kansas  and  Indian  Terri- 
tory. It  is  now  the  leading  producer  of  zinc  ores,  being  credited  in 
1903  with  a  total  of  227,689  short  tons  and  an  estimated  production 
for  1904  of  207,738  short  tons/'  The  ores  are  characterized  by 
high  grade,  the  ordinary  sale  basis  being  a  content  of  60  per  cent 
metallic  zinc.  Probably  an  average  for  the  recent  production  of  the 
camp  would  be  58  per  cent  metallic  zinc.  They  contain  as  marketed 
small  amounts  of  lead  and  cadmium. 
Mr.  George  Waring  quotes  the  following  analysis  as  the  average 
of  2,145  recent  shipments : h 
Average  analysis  of  Joplin  ore. 
Per  cent. 
Zn    57.75 
Fe    2.32 
Pb 1.07 
Cn    .042 
Cd    . .  388 
The  bulk  of  the  ore  is  used  for  the  production  of  spelter,  and  up 
to  recent  years  the  combined  spelter  production  of  Missouri,  Kansas, 
and  Illinois  practically  represented  the  production  of  blende  in  the 
Joplin  district.  The  Kansas  furnaces  are  now,  however,  drawing  a 
considerable  portion  of  their  supplies  from  the  West,  while  (he  fur- 
naces of  northern  Illinois  purchase  enough  ore  in  Wisconsin  to  ripsej 
the  old  balance  of  trade.  The  carbonate  and  silicate  ores  of  the 
Joplin  district  have  in  part  been  used  by  local  furnaces  in  the  pro- 
"  Lend  and  Zinc  News,  January  9,  1905,  p.  57. 
"Waring,  Geo.  \\\,  Jour.  Am.  Cbem.  Soc,  vol.  26,  1901,  p.   16. 
