166 FIELD COLUMBIAN MuUSEUM—GEOLOGY, VOL. I. 
since the ‘“‘hornblende rock’’ of this region proves to be such in the 
specimens in the Museum collection. With this is associated ande- 
site and the rock described by Sefior Gamba as ‘‘ syenite.’’ Sefior 
Gamba collected in the China river region nineteen specimens repre- 
senting three mines. The series is as follows: 
‘6369. Syenite from the China river.” 
‘¢370. Hornblende, wall rock of the vein.” 
These specimens, which are not in the collection, by analogy with 
specimens of like name are considered to be andesite or trachyte and 
the schistose chloritic rocks derived from them. 
‘371. Decomposed ore.” 
372, [E 1131.] Quartz and pyrite from the Santander lode.” 
This is a rusty quartz with pyrite in large crystals and some 
blende and galena. 
‘©3273. Colorado ore from Santander lode.” 
‘¢374. Quartz, ore from the Boyala lode.”’ 
“375, [E1204.] Quartz and pyrite, ore from the Boyala lode.” 
‘©376. [E 1132.] Rich decomposed ore from the San Sebastian 
lode.”’ 
A honeycombed quartz with no visible silver-bearing minerals. 
‘¢377. Ordinary quartzose ore from the San Sebastian lode.” 
‘¢378. Pyrite, blende and galena, sche:derz trom the San Sebas- 
tian lode.”’ 
‘¢379. Pyrite, blende and galena, schezderz from the San Sebas- 
tian lode.’’ 
‘©380. [E 1202] Galena, schecderz from the San Sebastian 
lode.” 
About 15% of the specimen is pyrite. 
‘381. [E 1201.] Rich galena, schetderz from the San Sebastian 
lode.” 
The galena is mingled with about 5% of pyrite and occurs in 
quartz. The galena is very finely granular and contains pyrargyrite. 
‘¢ 382, Pyrite and blende, scheiderz from the San Sebastian lode.” 
‘383. [E 1200.] Pyrite and blende, scheiderz from the San 
Sebastian lode.”’ 
(384. [E 1199.] Pyrite and blende, schetderz from the San 
Sebastian lode.” f 
The galena is finely granular and contains pyrargyrite in quan- 
tity. 
“©3285. Andesite from the China river.” 
‘©3286, Andesite from the China river.’’ 
