6i 
extraction . From each of these specimens lines are likewise drawn 
to specimens of the substances formed from them in subsequent 
operations, and so on until the final products are shown. It is 
thus possible for the visitor to follow readily each step of the oper- 
ation. 
Case F. — The Cyanide process for the extraction of gold 
from low grade ore as carried out at Mercur, Utah. This process 
depends upon the solution of the gold from the ore by a dilute so- 
lution of cyanide of potassium and precipitation by metallic zinc. 
The case also contains a collection of concentrates from gold and 
silver ores, illustrating the process of enriching ores before smelt- 
ing by the removal of much of the worthless material by me- 
chanical means. 
Case Q,— Extraction of gold as practiced at the Argo Smelter, 
Colorado. This is a type of the processes where the gold is col- 
lected in copper by smelting and then isolated by a process of 
leaching or solution. 
Case H. — Extraction of silver and lead as practiced at the 
Unterharz, Germany. 
By following the labels it will be seen that this apparently 
complicated process is resolved into the frequent repetition of 
comparatively few operations. 
Case I. — Extraction of lead and silver by the reverberatory 
process and by the blast furnace process. These do not repre- 
sent the process of any particular smelter, but rather are general- 
ized forms of the two most important smelting processes. 
Case J. — Extraction of gold, silver, lead and copper as prac- 
ticed at the Oberharz, Germany. As with the process illustrated 
in Case G, the apparent complexity is due to many repetitions of 
few processes. 
The visitor should now pass to the eastern end of the hall and 
note the following special groups in the center. 
K. — Silver, lead and copper ore, Cordillera Hill silver mine, 
Peelwood, New South Wales. 
L. — Gold and silver ore, British Columbia. 
n. — Gold ore. A group of large specimens of free milling 
quartz from various localities. 
N. — Zinc-lead ore, Laurium, Greece, 
O. — Copper-silver ore, Lead ville, Colorado. Assays gold , $6. 
per ton; silver, 41 oz. per ton; copper, 18 per cent. 
