150 FIELD COLUMBIAN MUSEUM—GEOLOGY, VOL. I. 
“200. Conglomerate [agglomerate|, wall rock of the Otramina 
mine.”’ 
“202, _[E 1082.] Conglomerate | agglomerate], wall rock of the 
Otramina mine.” 
It is composed of quartz pebbles and lava fragments in a matrix 
of tuff. 
66203; Sandstone [7uf] like No. 198.” 
‘204. Rock intrusive in the sandstone of the Otramina mine.” 
‘¢205. Quartz and pyrites from the Otramina mine showing an 
exceptional thickness of the vein.” 
The vein here varies from one-quarter inch to one and one-half 
inches in width and is between walls of a light colored tuff, similar to 
that of specimen No. 202. The vein consists almost wholly of blende 
_and pyrite, with a little dolomite. In cavities occur small crystals of 
dolomite and cobweb-like forms of jamesonite. 
‘¢207. [E 1085.] Ore showing an exceptional width of the vein 
in the Otramina mine.” 
This specimen shows a width of six inches of branching vein. 
The vein here is brecciated like that of Zancudo. The veinstuff con- 
sists of blende and pyrite, with small quantities of dolomite enclosing 
fragments of tuff. 
‘¢208. [E 1084.] Ore from Cateador vein.” 
The formation is similar to that of the Otramina mine. The 
specimen is like No. 197 in width of vein, nature and appearance of 
veinstuff and attached country rock, but there is less dolomite 
gangue, 
‘‘20g. Ore from the Cateador vein.” 
‘210. [E 1097.] Ore from the Cateador vein.” 
Galena, pyrite and chalcopyrite, with dolomite, forming small 
irregular seams in tuff. 
‘‘ot1. [E 1098.] Ore from the Rose vein, same formation as 
at the Otramina mine.”’ 
A compact aggregate of pyrite and blende in about equal parts, 
with galena and some calcite and dolomite. The vein must be at 
least four inches wide. 
‘©212. [E 1099.| Ore from Las Vetas mine, same formation as 
at the Otramina mine.” 
_ Pyrite in large pyritohedrons and blende, in about equal parts, 
with some galena and much jamesonite, the whole on a white gritty 
tuff. . 
‘$213. Ore from Las.Vetas mine.” 
‘¢214. [E 1100.] Ore from; Las Vetas, mine.” 
