Columbia subject headings:
Harvard subject headings:
Geology--Appalachian Region, Southern--Congresses.
Precious metals--Appalachian Region, Southern--Congresses.
Sulfides--Appalachian Region, Southern--Congresses.
Volcanic ash, tuff, etc.--Appalachian Region, Southern--Congresses.
Princeton subject headings:
Precious metals--Appalachian Region, Southern--Congresses.
Sulfides--Congresses.
Volcanism--Appalachian Region, Southern--Congresses.