132 FIELD COLUMBIAN MusEUM—GEOLOGY, VOL. I. 
“‘metasomatic deposits in a brecciated zone of acid lavas, while the 
calcareous deposits are segregation veins in acid tuffs. A discussion 
of the features of these deposits will be found in the accounts of the 
various districts. The southern deposits include those around Titi- 
ribi, Supia, Caramanta and Manizales, some of which are across the 
boundary in the adjoining Department of Cauca. The mines of Anti- 
oquia are wholly gold mines, except for a few mines in the southern 
part, which partake of the characters of the deposits of Tolima, 
GOLD MINING DISTRICT OF REMEDIOS. 
Remedios, lat. 7° 10’ N., long. 74° 55’ W.,1s situated in the North 
Central part of Antioquia, a few miles south of the re-entrant angle 
made bythe boundary of the Department of Bolivar. It was founded 
in 1560 on the Ite river, a branch of the Magdalena, for the sake of 
the rich placers there. On account of the deadly climate it suffered 
several removals, but finally occupied the site of Las Quebradas, 
where it now is. For many years after its foundation the chief indus- 
try was placer mining. About 1840 the quartz veins began to be 
exploited, and now they much exceed the placers in importance. In 
1886 the veins were said to produce over 300 pounds of gold per 
month. As this gold ranges in fineness from 579 to 638, this ,corre- 
sponds to a value of over $43,000 per month. The ores are typical 
quartz-pyrite vein material. The quartz in the unoxidized specimens 
is hard and firm, and greatly exceeds in quantity the sulphide, which 
occurs as parallel bands of coarsely crystalline pyrite, with very small 
quantities of galena and blende. Other sulphides appear to be 
absent. A specimen from the Silencio mine indicates a seven-inch 
vein. The mines are represented in the collection by a much larger 
number of sulphide than of oxidized specimens, and the sulphides 
are clean and fresh, indicating that the mines, even with the neces- 
sary slowness of working, have reached a considerable depth. The 
surface ores are rusty brown quartz, locally called ‘‘ colorado,” from 
a Spanish word, originally meaning colored, but later coming to 
mean red or brown. In some specimens the gold is visible as coarse 
scales. These ores occur in quartz veins, which are horizontal or of 
slight inclination (vefas de sombre). The country rock of one mine, 
the Santa Isabel, is a dark, fine-grained, very basic hornblende 
gneiss. That of the others is a rock locally called syenite, but really 
an andesite or trachyte. A formation described asalimestone dike (1) 
is probably a vein of calcite. An intrusive of ‘‘ hornblendic” 
