GEOLOGY OF GILES COUNTY, VIRGINIA 
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17. Dark gray crystalline limestone, rather massive but with 
bedding concealed. Many crooked joints running in all directions 
developed by weathering. ' The lower six feet are coarser crystal- 
line than the rest, with threads and knots of chert throughout, 
calcite veins and bunches of crystals all through the member but 
increasing towards the top, where a mottled appearance is de- 
veloped. Some small shale lenses. Pyrite is present in cubes and 
pyritohedrons, and there are pseudomorphs of limonite and hem- 
atite after these crystals. Weathers dark to black with chert 
and calcite in relief. 20 feet. 
18. Color the same as in 17, but lower part has red streaks 
and spots. A dense, finely crystalline, felsitic appearing lime- 
stone in beds up to three feet in thickness. Several layers of 
light colored chert lenses and nodules occur. Calcite veins in 
places, with jointing rare and irregular. Weathers a rusty 
brown, not black. Bryozoans at the base. 11 feet. 
19. Limestone, a dove color below to red above with calcite 
veins white to green and crystal lined cavities. Bedding is not 
distinct. Upper part becomes crystalline and slightly arenaceous. 
Veins are often not completely filled. Joints are irregular. No 
chert. Weathers brown. 41/2 feet. 
20. Thin red shale, thicker limestone, thicker red shale, and 
six feet of sandy and shaly, red limestone constitute this unit. It 
is capped by a few inches of shaly sandstone, which has reddish 
and greenish streaks. No layers are constant, the shale is fissile 
and ferruginous with inclusions of limestones. There is a layer 
of chert nodules in the upper limestone. 9 feet. 
21. Dark blue, compact, fine grained, even layered limestone, 
mottled with light blotches of chert and calcite crystals. Joints 
are very rare but the formation breaks into even blocks to make 
good building stone. Weathers lighter but into a dirty brown. 
3 feet. 
22. Dark, red and green streaked, cross bedded sandstone, in 
two or three layers. White quartz in knots and crystals. There 
are also* crystals of calcite and pyrite and chert nodules. 
1 foot. 
23. Dark blue limestone layers of three inches tb three feet, 
which is darker above. Weathers a dirty gray to buff. The upper 
part has cavities lined with calcite and the entire unit has quartz 
