410 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 218. 
distance above the salt horizon. In the writer's opinion the latter 
supposition is the more probable. Unfortunately it was impossible to 
obtain records of the strata passed through in drilling the salt wells. 
It is known, however, that these wells start near the base of the 
gypsum-bearing beds and strike rock salt at a depth of about 200 
feet. The aggregate thickness of rock-salt beds passed through is 
said to be about 175 feet. 
By combining all these data, some idea of the thickness of the 
lower (gypsum and salt-bearing) member of the Greenbrier limestone 
may be formed. 
Section of low or member of Greenbrier limestone. 
Feet. 
Top of gypsiferous series to top of Buena Vista wells 100 
Gypsum-bear mg rocks and shales in deepest well 600 
Bottom of deepest Buena Vista well to top of salt beds, probably not over .. _ 100 
Salt beds and inclosing rocks 175 
Bottom of salt beds to Lower Carboniferous sandstones ? 
The thickness of the series in the Saltville-Plasterco basin must 
therefore be in the neighborhood of 1,000 feet. 
MINING AND TECHNOLOGY. 
THE GYPSUM INDUSTRY. 
The gypsum deposits in this area have been developed at a number 
of points along the trend of the belt. These developments will bo 
described briefly in order from northeast to southwest. 
The most northeasterly point at which gypsum has been found in 
the Holston Valley area is on the Buchanan property, located about 
3 miles Avest of Chatham Hill post-office. Several small openings can 
be seen here, one of which was being worked at the time of visit. 
This quarry was about 30 feel deep and 50 feel in length, exposing 
gypsum of very good grade. The product is crushed for use as land 
plaster in a mill located near the quarry. Extensive exposures of 
gypsum occur in the vicinity, but the difficulty of marketing the 
product has prevented the development of these deposits, only about 
300 tons per year being quarried. 
About 3 miles east of Broadford post-office, and some distance north 
of the river, gypsum is worked on the property of Mr. John D. Barnes. 
The inclosing shaly limestone beds here strike N. 80° E. and dip 40° 
SE. Black powder and hand drills are used in extracting the gyp- 
sum. The workings, at first in open cut, are now mostly under- 
ground, a slope having been run down on the dip of the beds, with 
pillars of gypsum left at intervals to support the roof. The product, 
which may amount to 500 tons a year, is carried by wagon to a land- 
plaster mill located at Broadford, on Laurel Creek. 
