INTRODUCTION. 
The following pages describe a collection of ores, rocks and min- 
erals which was prepared to illustrate the mineral resources of 
Colombia at the World’s Columbian Exposition. The major part of 
the collection was afterwards donated to the Field Columbian 
Museum. It was prepared by F. Pereira Gamba, a mining engineer 
of Bogota. The scope of the collection is indicated by the title of 
the original catalogue, ‘‘ Catalogue of the Mines in Actual Produc- 
tion in the Republic of Colombia.” In an answer to an inquiry, 
Sefior Gamba writes: ‘‘The collection sent by our government to the 
Columbian Exposition was entirely formed by me. I traveled 
throughout the country collecting the specimens and stones in 
such manner that there is not one specimen of ore or other rock which 
was not personally collected and examined by me, and I believe that 
the collection, as it was sent, is the most complete representation of 
our minerals and mineral wealth ever made. * * * It is not a 
show of chosen specimens, but a collection of the common ores that 
are mined here. * * * Isent specimens of all rocks interfering 
with the veins.” 
This collection merits attention for the light it throws upon the 
nearly unknown nature and mode of occurrence of the ores of one of 
the important gold-producing countries of the world. Gold was first 
mined by Europeans in Colombia in 1537, and during the sixteenth 
and seventeenth centuries it was the great gold producer of the world. 
It now ranks ninth among the gold-producing countries; for 1898 
its production of gold has been estimated as 5,868.7 kilograms, or 
about one and one-third per cent. of the world’s production for that 
year. During the last century and the early part of the present, 
accounts of the mineral resources of Colombia were given by Hum- 
boldt, Boussingault, Chevalier, and other travelers, and although later 
travelers have explored the country, they have paid but little attention 
to the geology and mining of the region. Asa result the knowledge 
of this region has not kept pace with the general advance of geolog- 
ical-knowledge, the advance made in our knowledge of ore deposits 
of late years and with the great changes in the science of lithology. 
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