142 FreELD CoLUMBIAN MusEuM—GEo.ocy, VOL. 1. 
phates. The operation has broken up a good part of the ore into 
a breccia, which, if recemented at any time, would have the app eats 
ance of a typical brecciated vein. 
‘¢120. Corundon [| €orundum?| from the Frontino mine.” 
‘¢r21. Corundon | Corundum?| from the Frontino mine.” 
“«722. Copper ores from the Frontino mine.” 
‘724. Quartz and pyrite, ore from the Frontino mine.” 
‘125. [E 1067.] Ore with telluride of gold from the Fron- 
tino mine.”’ 
One face of this specimen is a thin seam of quartz, containing 
numerous crystals of gold. Those projecting far enough from the 
matrix for determination are cubes modified by the octahedron. 
With the gold are a few scattered grains of telluride, in quantity 
too small for an exact determination of the species. The country 
rock attached to this specimen looks like a rather coarse-grained, 
light-colored diorite. Under the microscope it appears as a much 
decomposed, coarsely crystallized diorite, impregnated with calcite. 
‘¢726. Ores with telluride of gold from the Frontino mine.” 
‘‘727. Ores with telluride of gold from the Frontino mine,” 
‘728. Ores with telluride of gold from the Frontino mine.” 
‘*t29. Ores with telluride of gold from the Frontino mine.” 
‘¢130. Felsitic rock from the Frontino mine.’’ 
‘¢131, [E 1648.] Pyritic ore from the Frontino mines] 
This is chalcopyrite mixed with massive, very magnetic pyrrho- 
tite, with crystals of calcite in quartz. The pyrrhotite in this speci- 
men like that in No. i1g is rapidly decomposing. 
‘¢732>) Pyritic-ore:tromithe Prontinoimine 73) 
Anza is upon the eastern slope of the Western Cordillera, 
on the flanks of the Cauca Valley, about eighteen miles south 
of the city of Antioquia, the ancient capital of that department. 
The unusual case of a gold mine in limestone is presented by 
the Quiunda mine. This is a mine on an auriferous quartz vein in 
limestone. With the vein there occurs a chlorite schist, similar in 
character to the metamorphic andesites common in the Mexican 


. 
eee ee ee ee) eee ee oe  . ee ee! Pee 






mining regions. , 
From Anza, Senor Gamba collected eight specimens, represent- 
ing one mine: 
‘733. [E 1067.] Hornblendic rock from the Quiuna mine.” 
A green chlorite schist, of the usual kind, 7. ¢, a metamor- . 
phosed andesite. 
‘¢734. Hornblendic rock from the Quiuna mine.” 
