134 | SIERRA DE UMANGO 
Among the mineralogical characteristics of the two species may 
be mentioned, that the eukairite has a lead-white, granular habit 
with a brilliant lustre. The umangite shows in fresh fractures a 
reddish, dark colour and a high lustre. The habit is massive. | 
Crystals of both minerals are unknown. 
Other minerals associated with these are bornite and of secondary 
products principally malachite. 
The veins have no visible relations to eruptives. They are con- 
siderably younger than the granites. 
In the Umango area there are also some other occurrences of 
selenides, but of less importance. On the trail between the Puesto 
Umango and Tambillos there lies in a very broken ground a small 
mine called „la Millionaria“. The chief rock here is a mica schist 
and the veins are as in the former case transversal. Malachite alte- 
ration products are also here very abundant. 
In the Quebrada Agua de los Caballos situated in the eastern 
part of the Cerro Potrero Viejo another transversal vein cut through 
a gneissic rock. It contains abundantly hematite, gathered along 
the salbands of the vein. This occurrence was recently exploited 
(by a French prospector, 1914 gone off to the war). 
Bodenbender (1911) mentions the occurrence of umangite- 
and clausthalite(PbSe)-bearing veins with a calcite gangue mass, 
cutting through the Famatina granite in the vicinity of the Piedra 
Pintada in the Sierra de Safiogasta. Outside the Umango area 
there are selenide bearing veins to the north in the province of 
Catamarca, where umangite has been found in the mountains to 
the west of Tinogasta. No further facts are known about the ap- 
pearance of the veins here.! | ; 
Other selenide occurrences in the Argentine Republic are met with 
in the province of Mendoza, in the Cerro Cacheuta mining camp. 
1 G. Bodenbender: Communicaciones mineras & mineralögicas. VIII. Cria- 
deros de seleniuros de cobre etc. Boletin de la Academia Nacional de Ciencias 
en Cordoba. Tomo XVII. Cordoba 1903. 
