54 FIELD MUSEUM OF NATURAL HISTORY 
States, thence to the northeast and south along the Appala- 
chians. After these are placed the ores of Mexico, then South 
America, then Africa, Australia, and Europe. 
PLATINUM. 
A series of specimens illustrating modes of occurence of 
platinum from over twenty localities, including Washington, 
Oregon and California, the United States of Colombia, and the 
Ural mountains is shown. In all of these specimens the metal 
appears in the form of flattened grains often associated with 
iridium, osmium, palladium, gold, copper, and chromite. The 
grains are usually found in river beds or placer deposits. A 
complete series of rocks and soils bearing platinum, from the 
Demidoff Platinum mines, Nizhni Tagilsk, Ural mountains, is 
shown, as well as a series of concentrates produced by washing 
these in order to separate the metal. Some unusual uses of 
platinum are illustrated as follows: Russian platinum coin, for 
a time used as money; coins struck in platinum and gilded, 
which passed for gold in Portugal and Spain during the past 
century; imitation gold dust made of platinum grains plated 
with gold. 
GOLD AND SILVER. 
A series of specimens showing typical associations of gold 
with other minerals, as they are found in mining, is shown. A 
similar series of silver-bearing minerals shows those minerals 
which contain silver as an essential constituent and those min- 
erals commonly closely associated with silver in the mines. 
Placer gold deposits are represented by a collection of aurifer- 
ous sands and gravels principally from Alaska and California. 
All placer specimens are separated from the general collections 
and included in a single series. 
The collection of gold and silver ores is composed of a series 
of regional collections arranged in geographical order. The 
more prominent are: 
Auriferous quartzes from Alaska representing three widely 
separated regions. 
A series principally of silver-lead ores from the Kootenai 
District of British Columbia. 
A series chiefly of silver-lead ores representing the Okonagon 
and Stevens districts of Washington and the Coeur d’Alene of 
Idaho. 
