262 
ZINC  RESOURCES  OF  THE  UNITED  STATES. 
As  already  noted,  the  smelting  and  mining  centers  of  the  zinc 
industry  are  not  always  coincident.  In  the  United  States,  further- 
more, the  ore  from  the  separate  districts  varies  greatly  in  grade  and 
in  price,  so  that  the  statistics  of  production  of  the  metal  afford  but 
imperfect  knowledge  of  the  importance  of  individual  mining  districts. 
In  terms  of  tonnage  of  ore  the  leading  zinc-producing  districts  of  the 
United  States  are  the  Joplin,  the  New  Jersey,  and  the  Colorado. 
The  Joplin  ores  afford  the  main  supply  of  the  Kansas,  Missouri,  and 
Illinois  smelters,  though  of  recent  years  important  amounts  of  ore 
from  Colorado  and  smaller  quantities  from  British  Columbia  have 
gone  to  Kansas  for  smelting.  The  New  Jersey  ore  is  largely  burned 
to  oxide,  though  some  is  exported  crude  and  some  is  used  in  making 
spelter.  The  importance  of  the  New  Jersey  ore  production  is  not 
generally  recognized.  The  Colorado  spelter  and  oxide  production  is 
small  as  compared  with  its  output  of  ore,  which  has  been  very  rapidly 
increasing  of  recent  years.  At  present  it  is  impracticable  to  give 
complete  statistics  of  zinc-ore  production  in  the  United  States. 
In  the  table  beloAV  are  estimates  of  the  ore  production  of  the  lead- 
ing districts,  with  the  approximate  content  of  metallic  zinc.  The  fig- 
ures are  for  the  year  1904.  In  them  no  allowance  is  made  for  smelt- 
ing losses  or  for  the  ore  which  is  burned  to  oxide,  the  purpose  being 
to  show  the  ore  production  and  the  relative  importance  of  the  differ- 
ent districts. 
Estimated    zinc-ore  production  and  metallic  zinc  content  of  ores  for  leading 
districts. 
[In  short  tons.] 
District  or  State. 
Zinc  ore. 
Zinc  content.   1 
Joplin             .  „     .   .      . 
263, 243 
250, 000 
197. 000 
19, 300 
21.000 
150, 048  1 
58, 750  1 
49, 250  1 
10. 500  I 
8.400  J 
New  Jersey  .  - ..  . . . 
Colorado ..._   
Wisconsin 
New  Mexico 
.  The  total  production  of  spelter  to  the  close  of  1904  may  be  esti- 
mated at  2,225,000  short  tons.  In  addition  a  considerable  amount  of 
ore  has  been  burned  to  oxide  by  the  direct  process.  Since  1880  this 
has  amounted  to  616,000  short  tons,  equivalent  to  approximately 
533,000  tons  of  metal.  Since  1897  a  little  more  than  200,000  tons  of 
zinc  ore  have  been  exported.  This  has  mainly  been  of  middle  or  low 
grade,  and  it  will  probably  not  be  fur  wrong  to  assume  a  total  con- 
