INVESTIGATION OF NONMETALLIFEROUS ECONOMIC 
MINERALS. 
By C. W. Hayes, Geologist in Charge. 
The distinctly economic work being done by the Geological Survey 
has shown a steady growth in extent and importance since its organi- 
zation in 1879. As pointed out Iry Mr. Emmons, this was at first 
directed largely to the investigation of the ore deposits of the precious 
and semiprecious metals — gold, silver, mercury, copper, etc. With 
the extension of areal mapping in preparing the Geologic Atlas of 
the United States, investigation of the more widely distributed ores 
of iron, manganese, and aluminum and the nonmetalliferous minerals, 
as clay, stone, phosphate, coal, asphalt, oil, and gas, was taken 
up. The natural grouping of these two classes of mineral products 
and the importance of their investigation were recognized by organiz- 
ing, within the Geologic Branch of the Survey, in 1900, the two sec- 
tions of metalliferous ores and nonmetalliferous economic minerals. 
Since that time sj^stematic investigations of the nonmetalliferous 
minerals have been carried on, both in connection with areal geologic 
mapping and independently of areal work. It is impossible to 
describe in detail all of the work of this kind which has been done 
by the Survey, but its character and extent may be indicated by a 
brief mention of some of the more important investigations carried 
on in recent years. 
The nonmetamorphic iron ores have been studied chiefly in connec- 
tion with areal mapping, and their distribution is shown in the 
geologic folios for considerable areas in Virginia, West Virginia, Ten- 
nessee, Georgia, and Alabama. The same is true of manganese, ocher, 
stone, and slate. 
All known occurrences of bauxite, the ore of aluminum, have been 
visited and examined by Hayes. 
The slate quarries of Vermont and eastern Pennsylvania have been 
examined by Dale, and the more important slate localities in the 
Southern States by Keith and Hayes. 
Special studies of the marble belt of Vermont have been made by 
Dale, and Keith has mapped the marble of East Tennessee. 
The phosphate deposits of Florida have been investigated by 
Eldridge, and those of Tennessee by Ha.yes, Ulrich, and Eckel. 
Investigation of the coal fields of the United States has been of two 
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