106 W. Beam—Rocks of the Yellowstone Park. 
II. Rocks of the Park; by Wm. Bram. 
The following specimens are from collections made in 1878 
by Messrs. Peale and Holmes, geologists to the Hayden Survey. 
All the rocks so far examined are evidently of igneous origin, 
and, except the first, are trachytic. 
orphyritie obsidian.—From the divide between Yellow- 
stone ee and Upper Geyser Basin of Fire Hole River. 
Hardness, 6; sp. gr, 24. Fracture x terion fig 
Color, greenish black, semi-transparent. Fusibility When 
heated strongly, swells up to a white blebby mass. With borax 
on platinum wire, dissolves in large quantity to a clear glass. 
With microcosmic salt, leaves a skeleton of silica. : 
Analysis : 
Be es 77-00% 
LO aee OS aks ee ie 13°40 
MES Boia whee Cn eae es 1°25 
1 Fa Sea oe ng pmengange ei ie are: 1°19 
NSO S2to 0s Eee oe ee 
cieices icccemaer a ee 
H,0O (by ignition) "70 
; 100°59 
2. Pebble of quartz trachyte covered with a deposit from Eehinus 
Geyser.—Pebble about one and a half inches in diameter, light 
fawn in color, and egy a tigi masses of transparent 
os silica. Hardness sp. gr., 2°6. Nearly infusible. 
Turns white when strongly, Om Gives with borax a clear 
bead, Cond with microcosmic salt leaves a skeleton of silica. 
The powdered mineral is slightly acted upon by hydrochlori¢ 
acid, and the filtered liquid does not contain any sulphates. 
The analysis gave : 
RO, naan naan nen wenn een Ta OO 
BLO. + FeO FT cease nw ew ce 14°55 : 
OnG coro ee “40 
MD os a ane ee ae trace 
K, a pens Mee in wee 63 
Na eee rarer yr reror a 2°10 
H O (be ignition) wicca 1°00 
100°58 
* Very little Fe.Os3. 
Other specimens are being examined and will be reported 
upon soon. 
715 Walnut street, Philadelphia. 
