DEPARTMENT OF GEOLOGY 
51 
tains the lead ores of the Mississippi Valley. These represent 
the group of nearly silver-free lead ores from v^hich a large 
part of the lead produced in the United States is derived. The 
larger number of specimens in this series represent the more 
important localities in Missouri, Kansas and Wisconsin, while 
a lesser number adequately represent the lesser production of 
various localities in Iowa, Illinois and Kentucky as well as 
several regions of minor importance. The gold and silver min- 
ing districts of Colorado are represented by more than 500 
specimens, which fill the remaining two and one-half wall cases 
against the south wall. They are grouped acording to mining 
districts and illustrate the great variety of the ores of this 
state. 
The ores of Nevada occupy one section of the case which 
stands against the southern end of the west wall. The series 
contains ores from many parts of the state. The more promir 
nent groups are a series of about fifty specimens from the 
Comstock Lode and a series of the ores and rocks of the Gold- 
field and Tonopah districts. 
Another section of the same case contains a very diversified 
series of ores of both gold and silver from Utah. These 
include the brilliantly colored ores of Mercur and the peculiar 
fossiliferous sandstone from Silver Reef. 
With the ores from Utah is placed a collection of gold ores 
from the Black Hills, South Dakota, which presents a good 
example of the great variety of gold ores which may occur in a 
limited area. Compare, for example, the ore from the Home- 
stake mine with that from the Holy Terror, which again is 
wholly different from that of the Golden Reward mine. In 
Hall 79 may be seen ores of yet different characters from this 
region, some carrying tin, tungsten, etc. 
The section of this case which is nearest the entrance to 
Hall 71 is occupied by a series of ores from western Montana 
and Idaho, another from Washington and a third from Oregon. 
Another case upon the west wall contains ores of California 
and Arizona. Of these California is represented by a series of 
typical gold-bearing quartzes, and the series from Arizona 
includes sufficient silver-copper and gold-copper ores to present 
somewhat the appearance of a collection of copper ores. With 
