DEPARTMENT OF GEOLOGY 
S9 
Gold ore, Alma, Park county, Colorado. 
A collection of nearly all the known alloys of gold and silver 
with other metals is shown. It contains polished plates of each 
alloy with specimens of the materials of which it is composed 
placed beside it. The color of rings or other articles of jewelry 
may be compared here with gold plates of the different degrees 
of fineness. 
A collection illustrating methods of saving gold and silver 
practised by Tiffany and Company, New York, is also shown. 
It includes wash water, concentrates from an exhaust blower 
that collects the dust of the shops, pieces of flooring of the shops, 
and shoes worn by workmen. Beside each of these are placed 
buttons of gold and silver obtained from articles of size similar 
to those shown. 
Hall 77. 
WEST DOME. 
Beneath the center of the dome stands a statistical column 
giving the bulk of each product of the mines of the United States, 
in 1892, for one second of time. Multiplying this by the num- 
ber of seconds in a year (31,536,000) will give the annual pro- 
duct. This column was built according to data given by the 
United States Geological Survey. In the four niches are pyra- 
mids of ore, containing respectively gold and silver ores; tin 
ores; iron ores; copper ores. 
The four large specimens surrounding the column are re- 
spectively: Iron ore; silver ore; iron ore; nickel ore 
This hall also contains collections of lead ores as distinguished 
from lead-silver ores. These as represented come mainly from 
the Mississippi valley. Here are installed also many lead-silver 
ores similar to those in Hall 72. 
Hall 79. 
Frederick J. V. Skiff Hall. 
ORES OF THE BASE METALS. 
The collections in this hall comprise ores of iron, copper, tin, 
zinc, nickel, manganese, mercury, and antimony, together with 
various metals and metalloids of minor importance. The ores 
of each metal are grouped together. 
Under each group are placed type specimens of the different 
