FOREIGN ORES. 
S3 
Silver. 
Case 22. — Silver ores have been mined for from the earliest 
recorded periods of man’s history. Throughout Spain, France, 
and Britain it is quite clear that the Romans eagerly searched 
for this metal, as they have left behind them numerous remains 
of their mining and smelting operations. The silver mines of 
Mexico have been much celebrated since the conquest of that 
country by Cortes in 1519. 
The most productive silver mines in the world have been 
those of America, — formerly those of Peru and Mexico, and 
in recent years those of the Western States of North America. 
The greater part of the silver extracted by mining in Peru is 
found in a species of ore locally called pacos ; it is a brown oxide 
of iron, with sil ver disseminated through its mass in exceedingly 
minute particles. The ore of Chile is similar. 
Silver mines of extraordinary value have been developed in 
recent years in the Western States of North America, especially 
in Nevada, Colorado, Idaho, Montana, and Utah. Perhaps the 
most interesting of these discoveries of silver ore are those in 
Nevada which date from 1859. Workings of enormous value 
have been opened in the neighbourhood of Virginia City and at 
other points on the famous Comstock Lode. 
Among the silver minerals exhibited in the case before us are 
some highly interesting specimens of the native metal, the fine 
solid masses from Chile being especially noteworthy. The 
remarkable association of this metal with native copper in the 
Lake Superior specimens has already been noticed (p. 78), 
Combined with sulphur, either alone or associated with 
antimony or with arsenic, silver forms a series of beautiful and 
valuable minerals. Of these the ordinary sulphide called 
Argentite, vitreous ore, or silver glance , is a soft and highly 
malleable mineral, assuming a series of cubic forms closely 
related to those of galena. Passing over the rare Saxon mineral 
Miargyrite, we may notice among the antimonio-sulphides of 
silver the beautiful species called Pyrargyrite , ruby blende, or 
dark red silver ore, of which the Mexican mines have contributed 
some magnificent hexagonal crystals ; whilst from Saxony is 
exhibited a specimen of light red silver ore or Proustite, a 
mineral chemically differing from the last species in containing 
arsenic in the place of antimony. To the same class of minerals 
belong Stephanite, or brittle silver ore, the rare species called 
Fireblende, and the mineral known as Polybasite in which the 
silver is partially replaced by copper and the antimony by 
arsenic. 
Another group of silver ores is formed by the combination of 
the metal with chlorine and its allied elements. The chlorides, 
bromides, and iodides of silver so formed, of which a few 
specimens are exhibited from the South American mines, are all 
affected to a greater or less extent by the action of light. It is 
notable that iodide of silver when heated, instead of expanding, 
slightly contracts in bulk. 
