2 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62. 
cavities are subjects of some interest, especially since the minerals of 
the vesicular cavities of the basalt of this great area have heretofore 
been given little attention. 
Grateful acknowledgment is due Mr. Fair for his part in discover- 
ing and making available the materials for study and in furnishing 
information relative to their occurrence. With the single exception 
of the cristobalite all of the minerals mentioned were correctly iden- 
tified by their collector. 
As a preliminary to the description of the minerals of the basalts 
it is considered pertinent to offer a summary of available informa- 
tion relative to this great area of lava flows known collectively as 
the Columbia River Basalt Plateau. 
THE COLUMBIA RIVER BASALT.? 
The Columbia Basalt area, including the Snake River lava of 
Idaho, forms one of the greatest lava regions of the world, being 
comparable only to the Dekkan Traps of India, which cover about 
the same area and have a similar composition and many other fea- 
WE 
VANS 
\\ 
Fic. 1.—SHOWING APPROXIMATE EXTENT OF COLUMBIA RIVER BASALT AREA. (AFTER CAMPBELL. 
U.S. GEOLOGICAL SURVEY BULLETIN 611.) 
tures in common. The total area covered by the lavas has been 
variously estimated as from 200,000 (518,000 square kilometers) to 
250,000 square miles (648,000 square kilometers), and includes the 
3This account and the accompanying figure 1 taken from M. R. Campbell. U.S. Geological Survey 
Bulletin 611, pp. 165-166, 1915. 
