Mar. 1899. THE Ores oF CoLtomBiA—NICHOLS. 127 
of my study to determine accurately the minerals and rocks of this 
collection and the nature of the deposits, so far as this is possible, 
from an examination of the specimens. For this purpose every speci- 
men in the collection has been carefuily examined, all doubtful min- 
erals have been tested, and slides of all rocks have been made and 
studied. Of course, the names of the rocks, as thus determined, 
differ from the local names given in the catalogue. Many rocks, the 
specimens of which were not available for study, have been deter- 
mined by the aid of the fragments of rock which cling to the ore 
specimens. In the catalogue following, the specimens have been 
listed under their respective mining districts. Besides such data 
upon the nature of the deposits as could be gathered from the cata- 
logue and from a study of the specimens, there has been prefixed to_ 
the list from each district such brief account of the location, charac- 
ter and importance of the district as could be gathered. The data 
for these accounts was obtained for the most part from the works of 
Vicente Restrepo and Elisée Reclus. The specimens which are in 
the collections of the Field Columbian Museum are given the Museum 
catalogue number in the lists on the following pages, and may, by 
this means, be distinguished from those specimens which are missing 
from the present collection. The results of study of these specimens 
have been incorporated in the catalogue. As this is‘a collection from 
those mines only which were in operation in 1892, it obviously does 
not include specimens from all the old mines worked when Colombia 
was at the height of her importance as a gold producer. Also, it can- 
not contain specimens from any mines which may have been opened 
during the last seven years. Nor does it bear upon the potential 
resources of the country in the form of undeveloped deposits, which 
is, on the whole, advantageous, for it confines the collection to speci- 
mens from deposits of known value. The secondary deposits, z. ¢., 
the placers, of Colombia are not represented in this collection. This, 
indeed, is not customary, for very little may be learned from such a 
collection of gravels. Within these limitations, the collection was, 
in its original form, practically complete. It is not improbable, how- 
ever, in a country where travel is as difficult as it is in Colombia, that 
a few isolated mines were overlooked, as might be done without im- 
paring, in any material way, the value of the collection. One such 
mine with a twelve-stamp mill was noticed by Dr. G. A. Dorsey, of 
the Museum, at Ensolvado, in the Upper Cauca valley, near Popayan 
