Mar. 1899. Tue Ores or CoLomBia—-NICHOLS. 133 
(chloritic) material is described in the catalogue as occurring in the 
Cordova mine, and a porphyritic rock occurs in like manner in the 
Providencia mine. 
From this district Senor Gamba collected 61 specimens, repre- 
senting twelve mines. The series is as follows: 
‘*t. Syenite, the wall rock of all veins of the district.”’ 
The term ‘‘syenite’”’ seems to be locally applied to any gray, 
granular, quartz-iree rock. In this instance, judging from fragments 
enclosed in specimen No. 15 and others, the rock is an andesite or a 
trachyte. The specimens examined were too much altered by the 
action of the vein liquors for exact determination. 
Syenites and granites are constantly referred to, not only in this 
catalogue, but in all works on the subject. Whenever it has been 
_ possible to examine the specimens, the author has invariably found 
them to be andesites or similar rocks. It may be noted here that 
Chibas,* quoting Karsten, says: ‘‘During the upheaval, volcanic 
forces seem to have been very active in some portions of the country 
and eruptions of porphyry, granite and syenite took place.’’ This 
would seem to indicate that volcanic rocks were referred to under 
these names. 
‘2. Hornblendic material, intrusive in syenite in the Cecilia 
vein.” 
Here and generally in this catalogue, the expression, ‘‘ horn- 
blendic material,” or ‘‘hornblendic rock,” is to be interpreted as refer- 
ring to an eruptive rock which has become very chloritic through 
alteration. This specimen doubtless corresponds to the chlorite 
schist of No. 133. 
«¢3. Ore from the Cecilia vein.”’ 
‘4. WVeinstuff from the Cecilia vein.” 
‘¢5. Decomposed ore from the Victoria mine.” 
‘*6. Decomposed ore from the Victoria mine.”’ 
‘7, Clay from the vein, Victoria mine.” 
‘¢8. Hornblendic material, intrusive in Cordova mine.’’ (See 
No. 2.) 
‘*g, [E 1650.|] Quartz, ore from the Cordova mine.” 
This is a clean, milky quartz, with slight iron stains. A few 
scattered galena crystals are present, but no pyrite. 
‘¢to. Quartz, ore from the Cordova mine.” 
‘tr. Quartz, ore from the Cordova mine.”’ 
“72. Quartz, ore from the Cordova mine.” 
‘73. Quartz and pyrites, ore from the Cordova mine.” 

FI-Oc, cit: 
