, 
352 Geological Chemistry of Yellowstone National Park. 
Rocks of the Park ; by Witu1am Beam. 
3. Rock from Yellowstone Cafion near Fails.—Consists of 
white, opaque fragments, rough to the touch. Fracture con- 
choidal, texture porous. Hardness, 35; sp. gr., 2°36; fusi- 
bility, 55. Gives a colorless bead with microcosmic salt and 
borax; moistened with cobalt nitrate and heated, it turns 
bright blue. Hydrochloric acid dissolves 14°6 per cent of the 
powdered mineral. Analyses gave: 
SiO weasels cae. 64°60 
Al,O, and Fe,0, _. 25°65 
fe, traces 
ho se 
Radigh te he oS see en en See 43 
i oo 8-70 
100°14 
The rock has the appearance and qualities of a very compact 
or baked clay; it eres strongly to the tongue; when 
cause. 
4. Trachyle from Junction Valley.—The pieces were greenish- 
blue, interspersed with white and dark spots and small particles 
of free silica. Fracture uneven. Hardness, 4°5; sp. gr., 2°84 ; 
fusibility, 55. Gives reaction with borax for iron. Heated 
with cobalt nitrate, the whole parts become blue and the rest 
brown. Composition: 
oO ER ania Fo re Pe 69°90 
AO ee 17°58 
i ee eae ene Ti NRIRS See ba 2°41 
ino a ee 
KO ee ae 
Mo as ee 2°41 
H,O by ign eae ee os eae 3°65 
