156 FIELD COLUMBIAN Mus—EUM—GEULOGY, VOL, I. 
SILVER AND GOLD MINING DISTRICT OF MANIZALES. 
Manizales, founded in 1848, is a town of rapid growth, having, 
in 1880, 14,600 inhabitants. Mining is not the principal industry 
of the place, for it is the most important commercial center of South- 
ern Antioquia, and has valuable farming and grazing interests. It 
is situated upon the boundary between Antioquia and the Depart- 
ment of Tolima, upon a terrace of the Sierra del Quindiu, or Central 
Cordillera of the Andes, and upon the northern bank of the Chinchina, 
a river which empties into the Cauca. The ores of this district, 
like the others of Southern Antioquia, consist largely of blende with 
pyrite. In addition, antimonial ores occur in the form of stephanite, 
brongniardite, tetrahedrite, and pyrargyrite. These ores occur in 
quartz and calcite. There is nothing about the specimens to indicate 
their mode of occurrence. The region is volcanic, and the specimens 
of country rock examined proved to be trachytes and rhyolites. 
Specimens of country rock from Manizales and vicinity are listed 
by Sefior Gamba as ‘‘porphyritic syenite,” ‘‘quartzose schist,”’ 
‘‘trachyte”’ and ‘‘tuffs.”” Of these, the ‘‘porphyritic syenite”’ proves 
to be a rhyolite, and the ‘‘quartzose schist” atrachyte. The term 
syenite is here, as elsewhere in Colombia, the local name given 
to some lava. 
From Manizales Sefior Gamba collected twenty-one specimens, 
representing six mines. ‘The series is as follows: 
‘¢292. Syenite, wall rock of some of the veins.” 
This specimen, not being in the collection, could not be examined. 
For reasons given under the first specimen entered in the catalogue, 
this rock is here considered to be a trachyte. 
‘¢293. Decomposed quartzose ore from the Diamante mine.” 
“¢294. Decomposed quartzose ore from the Diamante mine.”’ 
‘©295. Quartz with pyrites, freibergite (argentiferous tetrahe- 
drite) and ruby silver, from the Morisco mine.” ; 
‘¢296. Colorado ore from the Diamante mine.”’ 
‘$297. [E 1121.] Porphyritic syenite, wall rock of the Morisco 
mine.’”’ 
This is a light grey, very acid rhyolite, thoroughly kaolinized. 
«298. [E 1122.] Antimonial silver from the Morisco mine.” 
This is a specimen of vein quartz, with druses of quartz lining 
cavities. Upon the walls of these cavities small spherical aggregates 
of stephanite are found. 
‘¢299. Antimonial silver ore, rich in brongniartine.” 
This mineral is a sulph-antimonide of lead and silver. 
