—— 
Mar. 1899. THE Ores or CoLtombia—NICHOLS. I7I 
abandoned. Since that date one or more mines at Alta, Baja and 
Vetas have been worked at intervals, but usually without any con- 
tinued success. As Sefior Gainba did not include these districts 
in his collections, it may be inferred that in 1892 no work was 
being carried on. 
The veins are of blue quartz, traversing a rock described as 
essentially feldspathic, which alternates with a diorite, and some- 
times with a granite. These veins vary in width from one to four 
centimeters, and rarely attain.a width of ten or fifteen centimeters. 
The ores from some of the mines were described as sulphides of silver, 
zinc, antimony, lead, and iron. According to Boussingault, placers 
occur in a decomposed schist at the base of a ‘‘bed” of a schistose 
micaceous gneiss. The specimens in this collection do not throw 
any light upon the nature of the above-mentioned ‘‘ roche essentielle- 
ment feldspathique,”’ nor are there any specimens of diorite, granite, 
or other country rocks. The gangue is a very dark ‘‘blue quartz’”’ 
in most specimens. In some there is a light-colored quartz. The 
only accessory mineral noted was aragonite coating quartz. The 
metalliferous minerals, occurring in these specimens, are pyrite, 
pyrrhotite, chalcopyrite, blende, enargite, freibergite, malachite, 
azurite, native gold, and native silver. For further information 
upon this subject the reader is referred to the work of Vicente 
Restrepo above cited. An article upon Pamplona, by Carl Degen- 
hardt, in the Monatsberichte tiber die Verhandlungen der Gesellschaft 
fiir Erdkunde zu Berlin, 1842, contains a map of the Baya district. 
