52 FIELD MUSEUM OF NAT URAL HISTORY 
the ores from the Tombstone region are a series of the rocks 
of the district among which the ores occur. 
The cases along the north wall contain ores of New Mexico, 
Mexico, South America and Australia. • n ^ a 
The series of ores from New Mexico presents chiefly lead- 
silver ores, among which the galena from the Hillsboro region, 
and the “carbonate” lead-silver ore and galena of the Magda- 
lena Mountains, are prominent. Ores of other classes, mclu - 
ing those of silver-copper from the northern part of the terri- 
tory and various types of gold-silver ores Irom the Galhnas 
Mountains are also represented. 
The series of Mexican ores includes representative speci- 
mens of ore from all the gold and silver mining states of that 
republic, accompanied, in the case of the more important dis- 
tricts, by specimens of the country rock. The collection is espe- 
cially interesting as showing the association of the ores wit 
eruptive rocks such as are characteristic of most of the richest 
silver deposits of the world. 
The series of ores representing South America is composed 
chiefly of specimens from Colombia, Ecuador, Brazil, and Vene- 
zuela. Tbe collection of Colombian ores is especially complete 
and includes typical specimens of ores, gangues and rocks from 
practically all the mining districts of that country. This region 
was the ancient “El Dorado,” or land of gold, from which came 
the first important yield of gold in the New World, and of whic 
many wonderful stories were circulated. 
The collections representing the ores of Australia consist 
principally of silver-lead and silver-copper ores. Many of the 
specimens are too large for the serial cases, and shou e 
sought in the large center cases and in the West Dome. 
A wall case upon the east wall contains the ores of Europe 
and ores from other parts of the Eastern Hemisphere. 
Of these the series from Great Britain consists of both lead- 
silver and gold ores. The lead-silver ores illustrate well some 
of the common associations of galena. Galena is commorily 
associated with pvrite, but here we find it mixed with blende, 
a zinc ore which is very troublesome to the lead smelters. Speci- 
mens from the Welsh mines which contain much blende are 
marked “poor ground.” A good specimen of fluorite shown 
here, illustrates another common associate of galena in the Kng- 
