58 FIKLD MUSEUM OF NATURAL HISTORY 
2. 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 solution 
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. 
3. Extraction of gold as practised 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. 
4. Extraction of lead and silver by the reverberatory pro- 
cess and by the blast furnace process. These do not represent 
the process of any particular smelter, but rather are generalized 
forms of the two most important smelting processes. 
5. Extraction of silver and lead as practised in the Unter- 
harz, Germany. By following the labels it will be seen that this 
apparently complicated process is resolved into the frequent 
repetition of comparatively few operations. 
6. Extraction of gold, silver, lead, and copper as prac- 
tised in the Oberharz, Germany. As AHth the preceding process 
the apparent complexit}^ is due to man}^ repetitions of a few 
processes. 
]\Iany specimens too large to be installed in their proper geo- 
graphical order may be found in special cases and upon pedes- 
tals. These serve to give a truer idea of the appearance of the 
ores than the smaller specimens. They include: 
Silver, lead, and copper ore, Cordillera Hill silver mine, Peel- 
wood, Xew South Wales. 
Gold and silver ore, British Columbia. 
Gold ore. A group of large specimens from various localities. 
Zinc-lead ore, Laurium, Greece. 
Copper-silver ore, Leadville, Colorado. 
Group of large specimens of gold ores from American locali- 
ties. 
Gold-copper-silver ore, Ouray county, Colorado. 
Auriferous quartz, San Miguel county, Colorado. 
Group of large specimens of refractory gold ores. 
Block of ore from the forty-foot level of the Back Creek sil- 
ver and gold mine. New South Wales. 
