SALT AND GYPSUM DEPOSITS OF SOUTHWESTERN VIRGINIA. 
By Edwin C. Eckel 
INTRODUCTION. 
The field work on which is based the following report on the Vir- 
ginia salt and gypsum deposits was carried on by the writer during 
August, 1902, under the direction of Dr. C. W. Hayes. The writer's 
thanks are due to the gypsum producers of the region, who cordially 
cooperated with him in his investigations. 
Though salt and gypsum are found elsewhere in Virginia, the only 
economically important deposits of these minerals occur in the south- 
western portion of the State. These deposits are located along the 
valley of the North Fork of Holston River, and have been developed 
quite extensively in Smyth and Washington counties. 
The occurrence of salt brines in the Holston Valley was known at 
least as early as 1781, as Jefferson mentioned the fact in his Notes 
on Virginia. Rock salt was not, however, discovered until 1840. 
Gypsum or "plaster" seems to have been recognized early in the 
nineteenth century, though the writer has not been able to ascertain 
the exact date of its discovery. 
Though the salt and gypsum deposits have been long known and 
worked, and have been examined by many geologists, a wide range 
of opinion exists as to their age and origin, as will be seen on com- 
paring the literature of the subject. It is sufficient in this place to 
note that, as to age, the deposits have been variously referred to the 
Silurian, Carboniferous, Triassic, Tertiary, and Pleistocene, while 
different authorities have considered them as originating from deposi- 
tion from sea water, from deposition from lakes, by the decomposition 
of pyrite and resulting action on fragments of limestone, or by the 
action of sulphur springs on unweathered limestone. 
The work of the last field season would seem to prove that both the 
salt and gypsum deposits originated from deposition, through the 
evaporation of sea water in a partly or entirely inclosed basin, and 
that they are of Lower Carboniferous age, being immediately overlain 
by the massive beds of the Greenbrier limestone and underlain by 
Lower Carboniferous sandstones.. 
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