FIRST MINING EXPOSITION AT DENVER, COLORADO 
87 
Bocky mountains west from Denver is coloured as metamorphic rocks. Nőt 
very far to the west the newer eruptive rocks make their appearance as 
well, as to the east close by to Denver Basalt and extensive beds of rhyo- 
litic tufa beds are to be found. It is therefore probable, that their mass 
has a continuation under the gold-bearing metamorphic rocks, and that 
tliey liave caused the formation of the metallic veins in the older overlying 
surface rocks, wliich may liave occured in the newer tertiary period in the 
Pacific State as well as the case is in Hungary. 
Besides the telluric ores Hornsilver was exhibited in very great más- 
ses. The external features of this are nőt at all attractive, the surface being 
covered by a yelloish ochre, bút it possesses the interesting physical pro- 
perty of being sectile, wliich has been shown by the blade of an axe, ha- 
ving penetrated intő its soft mass fór nearly half its breadth. There was 
exhibited a pyramide, corresponding to a silverblock extracted from the 
cerargyrite in 1 7 1 /a hours from Bobért E. Lee mine, Leadville, Colorado. 
Yalue D. IIS‘500. 
From Utali I saw sandstones with carbonized plants, containing na- 
tive Silver, of wliich the greatest part was condensated on the hlack leaves 
of this sedimentary rock. Te quantity of this extraordinary formation is 
said to he great. 
Arizona exhibited samples of native Silver of the same beauty as 
those, wliich came from Mexico, and a great varietv of copper ores. 
Minerals were exposed hy somé dealers, bút mucii more was seen in 
the curiosity sliops, wliich are very abundant in Denver, and where somé 
american mineral localities are well represented. 
I mention only the granitie formation of the Pike’s Peak mountain, 
where the green Amazonites, as a typical mixture of Microcline and Ortho- 
clase occur. It interested me to see somé of the accompanying minerals 
chiefly in the collection of Mr. Cross. Besides the Álhite, wliich we liave 
in our collections too, I saw large colorless Topazes very similur to those 
from the Ural; together with the Topáz Phenakite is to be found. In one 
Quartz-vein of the Pikes’s Peak gránité Cryolite in imbedded, wliich som- 
times contains bluisli Tliomsenolite, bút Mr. Cross had nőt yet found the 
Pachnolite. In the same district (Eureka tűnnél) the Quartz vein of the 
gránité contains a nest, in wliich beautiful crystals of Zircon with reddisli 
Fluorite and Kaolin are to be found. 
Bút the most interesting miueralogical novelty of the Pike’s Peak are 
the imbedded hexagonal crystals of Tysonite and Bastnásite, the for- 
mer a fluoride of Cerium Lantham and Didym, the latter a produc-t of a 
partfal alteration, the result of taking up somé carbonic acide in order to 
fönn a combination of the íluorides with the carbonates of the same rare 
elements. • 
