134. FieLD CoLuMBIAN MusEuM—GEOLOoGy, VOL. I. 
‘‘r4. [TE 1047.] Quartz and pyrites, ore from. the Cordova 
mine,”’ 
.This is a white, milky quartz, with stained seams. It contains 
about 25 per cent. of pyrite in large cubes. 
‘15. [E 1048.] Quartz and pyrite, ore from the Cordova 
mine.’’ , 
This is a white, milky quartz, with iron-stained seams weathered 
in about aninch. About 1o per cent. pyrites and galena in about 
equal quantities partially fill cavities which extend through the speci- 
men in the form of parallel bands. Some open seams are lined with 
crystals, and-there are inclusions of a granular kaolinized material, 
which is apparently a decomposed acidic country rock. The pyrite, 
in the form of pyritohedrons, was deposited in part simultaneously 
with the galena and in part later. This is shown by crystals com-, 
posed of galena, which enclose pyrite in irregular forms, and are 
partially enclosed, in turn, by pyrite. There are also pyrite crystals 
on galena. 
‘¢16. Quartz and pyrite, ore from the Silencio mine.” 
‘“¢77, [E1049.] Quartz and pyrite, ore from the Silencio mine.” 
This is crystallized and milky quartz, with about 5 per cent. 
of pyrite in detached crystals. There is a comb structure of quartz 
crystals through the center, and the pyrite forms a band on either 
side. A little blende sometimes occurs enclosed in pyrite crystals. 
It contains enclosures of andesite or rhyolite, similar to those of 
specimen No. 15. 
‘18. Quartz and pyrites, ore from the Silencio mine.’ 
‘‘tg. Quartz and pyrites, ore from the Silencio mine,”’ 
‘¢20. ‘Quartz and pyrites, ore from the Silencio mine.” 
‘21, [E 1649.] Pyrites, ore from the Silencio mine.”’ 
‘¢22. Concentrates from the ore, Silencio mine.” 
‘23, Pyrites, ore from the Silencio mine.”’ 
‘24. Quartz, ore from the Silencio mine.’’ 
‘¢25. Quartz, ore from the Silencio mine.’’ 
‘¢26. Quartz, ore from the Silencio mine.”’ 
The mines listed above were worked at the time the collection 
was made, by an English company, the Frontino & Bolivia Mining 
Co. Most or all of these mines are on what was formerly known 
as the Bolivia vein. 
‘¢27, Ordinary quartzose ore from the Cristales mine.” 
‘¢28. Crystallized quartz from the Cristales mine.’’ 
‘¢29. Quartz, ore from the Cristales mine.” 
‘¢30.  Pyrites, ore from the Cristales mine.”’ 
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