GEOLOGY OF GILES COUNTY, VIRGINIA 
345 
and look concretionary but are not. Curved pieces break out 
giving rounded masses, but each has the same composition as the 
rock above and below. Red, ferruginous quartzitic sandstone 
with quartz veins. Weathering of the iron has gone on along 
these curved planes and thus has aided the spheroidal breaking. 
The lower two feet are rarely nodular but otherwise they have 
the same appearance. 51/2 feet. 
7. Red sandstone and arenaceous shales, which when first 
exposed, seem to be thick, massive beds. When weathered, the 
thin shaly beds appear and the rock crumbles. Fine and even 
grained with little cross-bedding. Regular for long distances. 
Usually dark, brick red, rarely gray. Scattered green blotches 
occur as well as calcite veins. Fine flakes of mica are probably 
primary but the chlorite veins are secondary. 47 feet. 
8. A covered interval, which from the float seems to be largely 
soft gray and green as well as red sandstones and shales. 
197 feet. 
Analyses of a Single Sample of the Bays Formation 
from near Glade Springs, Virginia.^^ 
(J. H. Gibboney, Analyst) 
Per cent 
Insoluble 90.18 
Alumina and Iron oxide 5.72 
Lime 0.64 
Calcium carbonate 1.14 
Magnesium 0.03 
Magnesium carbonate 0.07 
THE SILURIAN SYSTEM 
Introduction 
The Silurian rocks of Giles County are dominantly sandstones, 
(sometimes semiquartzitic) , but there are also interbedded 
shales, and a few conglomeratic layers. These rocks are divided 
into the Clinch and Rockwood formations, but in addition some 
rocks classed as the lower Giles may be in part Silurian. 
Silurian strata outcrop in a continuous band, about a mile and 
a half wide, along the northern border of the county, but do not 
extend into the panhandle because they dip south and thus in 
Bassler, R. S., “Cement Resources of Virginia,” p. 170. 
