57 
nize the presence of valuable metals. Opportunity is given by 
the numerous examples shown in this hall to study the slight 
indescribable variations in the appearance of a mixture of gan- 
gue minerals, which often indicate the presence or absence of the 
precious metals. It should be said, however, that all indications 
of this kind are often more or less deceptive and the only 
positive proof of presence or absence of gold or silver is to be 
found in actual trial by assay. 
The above observations do not apply, however, to the lead 
ores, which are readily recognized by one having acquaintance 
with the lead-bearing minerals. 
This hall also contains a collection of products from the 
metallurgical treatment of ores. These are so arranged that 
the separate steps in the treatment of the ores may be followed 
hy the visitor. 
PLATINUM. 
CASE A. — Specimens illustrating modes of occurrence of 
platinum in nature, from over twenty different localities, includ- 
ing Washington, Oregon and California, the United States of 
Colombia and the Ural Mountains. In all of these specimens 
the metal may be seen in the form of flattened grains often as- 
sociated w’th 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 Tagilisk, Ural Moun- 
tains 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 t'me 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. 
CASE 1. — Type specimens showing modes of occurrence of 
gold in nature. These are — crystallised gold; free gold in the 
vein-stuff ; pyrite containing gold disseminated through its sub- 
