162 FIELD CoLuMBIAN MustEUM—GEOLOGY, VOL. I. 
‘¢ 333. Black quartzose slate, wall rock of the Sonrisa mine, 
Marulandes.’’ 
‘€334. Quartz with arsenopyrite from the Sonrisa nine, Maru- 
landes.”’ 
‘¢335. Quartz with arsenopyrite from the Sonrisa mine, Maru- 
landes.”’ 
‘¢ 336. Quartz with arsenopyrite from the Sonrisa mine, Maru- 
landes.”’ 
SILVER MINING DISTRICT OF SANTANA. 
Santana or Santa Ana, five miles southwest of Mariquita, was 
reputed in the early days of Colombian mining to be one of the rich- 
est districts tributary to that city. After the general closing of the 
mines at the beginning of the 18th century, these mines lay hidden 
until they were rediscovered and opened by order of the Spanish gov- 
ernment in 1785. From then until now they have been worked 
at intervals. One of the richest of the old mines was the Santana 
mine. According to Vicente Restrepo, this mine, with three others 
in the district, was operated under government control from 1785, 
when it was rediscovered, until 1796, when it was abandoned as 
unprofitable. It appears to have been neglected again until 1824, 
when it was leased to private parties and operated with European 
machinery and management. For fifty years, or until 1874, mining 
was carried on by three companies successively, none of whom 
were repaid for the expenditures required. In 1874, when the mine 
was again abandoned, there were two shafts, one down 600 feet and 
the other goo feet, and at these depths the ore became very poor. In 
connection with other observations this fact points toward a rather 
interesting conclusion: These Cordilleras are composed of eruptive 
rocks set upon a base of crystalline and metamorphic schists includ- 
ing (near Santana and the volcano of Tolima) mica schist and slate 
which are flanked by Triassic sandstones. From nearly every mine 
mentioned in this catalogue there come specimens often disguised 
under local names, which are either andesites, rhyolites, trachytes, 
dacites or their derived tuffs. In the case of the great majority of 
these mines no other rocks are mentioned, except more basic erup- 
tives in very small quantities. The ores from the Titiribi district 
appear to be a product of a lateral leaching of surrounding lavas. If 
the other deposits in the lavas were similarly formed it would be 
expected that as the mines penetrated through the lavas into the crys- 
talline rocks below, the ores would diminish in value even though the 
