368 
BOLIVIAN COPPER DEPOSITS 
mines other workable vetas are encountered. No equally prom¬ 
inent ramos cupriferous beds outcrop, although some of the beds 
outcropping between the Libertad mine and the fault plane are 
beds that underground yield workable ore. 
Mineralization has taken place principally in beds of the Ramos 
series and the Vetas series close to the fault plane, but also to a 
limited extent in the fault plane itself. The characteristic manner 
of mineralization has been the impregnation of sandy beds by 
native copper. As until about six years ago no facilities were 
available for working sulphide ores such ores were disregarded 
and the extent of the sulphide mineralization not realized. 
No observations are available to indicate clearly the relations 
between the sulphide ores and the native copper ores, other than 
the general statement that the sulphides occur in the vetas near 
the surface and in depth pass over into the native copper ores and 
that the ramos ores are all native copper ores. In the Gullatiri 
Grande mine a streak of sulphide ore is encountered on the third 
level which is about 200 m. below the surface. In the Remedios 
mine, the sulphide ores extend to 200 m. below the surface and 
are there replaced by native copper ores. The upper levels of the 
Vizcachani shaft yield sulphide ores, but the lower levels are in 
native copper ores. The Umacoya veta in the Vizcachani shaft 
carries native copper ore to above the fifth level, a depth of about 
150 m., whereas the veta adjoining it in the hanging wall still 
contains the sulphide ores at this depth. The mines in the ridge 
north of Corocoro, the Estrella, Copacabana, Capilla, Malcocoya, 
and San Augustin are producing sulphide ores, but the depths to 
which they extend are not known. 
Ore deposition has taken place principally in arenaceous and 
pebbly beds and only in the ramos occasionally in shales. Typical 
native copper ore consists of nearly white to light-greenish sand¬ 
stone irregularly mottled with specks of copper. A thin section 
of this ore is made up of rounded to subangular grains of quartz, 
and a little plagioclase feldspar, ranging from .15 to .60 mm. in 
diameter and averaging .3 mm. The matrix of these grains is 
feldspar, chlorite, and a little calcite. The native copper occurs 
chiefly as a replacement of the matrix, penetrating the boundaries 
of the quartz grains to a very limited extent, in grains and flakes 
varying from .1-.3 mm. in diameter and averaging .15 mm. In 
