88 
[BULL.  260. 
GOLD   DERIVED   FROM   LEAD   ORES. 
The  lead  ores  of  the  Coeur  d'Alene  district  are  practically  free  from 
gold,  as  are  those  of  the  Mississippi  Valley.  The  principal  con- 
tributors to  this  class  are  Colorado  and  Utah.  Colorado  conies  first 
with  about  $4,000,000,  of  which  one-fourth  is  derived  from  the  Lead- 
ville  mines,  which,  as  stated,  are  exploiting  late  Mesozoic  replace- 
ment deposits  in  limestone.  The  rest  is  largely  due  to  auriferous  and 
lead-bearing  concentrates  from  Tertiary  veins  in  San  Juan,  Gilpin, 
and  Mineral  counties.  Utah  contributes  about  $400,000  from  lead 
ores,  nearly  the  entire  amount  of  which  is  obtained  from  the  Park 
City  silver-lead  veins,  which  are  believed  to  be  of  early  Tertiary  age. 
The  amount  of  gold  derived  from  lead  ores  in  1904  is  estimated  atl 
$4,600,000,  or  almost  the  same  quantity  as  that  derived  from  copper 
ores. 
SUMMARY. 
Summing  up,  we  have  the  following  tentative  distribution  of  the< 
gold  production  of  1904 : 
Placers $12,  900,  000 
Quartzose  gold  and  silver  ores  : 
Pre-Cambrian  quartz  veins $5,454,000 
Mesozoic  quartz  veins  (Pacific  coast  belt) 21,(500,000 
Tertiary    gold-quartz    veins     (Rocky    Mountains 
and  Great  Basin) 35,700,000 
Copper   ores 
Lead   ores  __ 
62,  754,  (XX 
4,  300,  OCX 
1  600,  00( 
Total. 
Source  of  production  of  gold  and  silver  in  1904. 
84,  554,  00(  i 
Placers 
Quartzose  gold  and  silver  ores: 
Pre-Cambrian  quartz  veins 
Mesozoic  quartz  veins  (Pacific  coast  belt) . 
Tertiary  quartz  veins  (Rocky  Mountains  and  Great 
Basin ) 
Total 
Copper  ores . 
Lead  ores 
Total 
Gold. 
Fine  on  nee: 
619, 700 
264, 000 
1 , 045, 000 
1,727,000 
3, 036, 000 
208, 000 
222, 500 
4,086,200 
Silver. 
Fine  on  nee s. 
64, 000 
71),  00 
860, 00 
11,000,00 
11,939,00 
18, 600, 00  I 
23, 000, 00 
53,603,00 
