1908] 
Flint-like Slate Near Chapel Hill 
7 
A partial analysis of the rock by Dr. A. S. Wheeler, associate 
professor of Chemistry in the University of North Carolina, gives 
the following results: 
Silica 77.54 per cent. 
Alumina 13.51 per cent. 
Iron oxide 1.17 per cent. 
Lime 1.10 per cent. 
Magnesia 0.23 per cent. 
This analysis confirms the microscopic determination. 
Hand specimens and thin sections of a somewhat similar fine 
grained siliceous rock from Gold Hill, N. C., collected last sum- 
mer by Mr. F. B. Laney of the North Carolina Geological Sur- 
vey, were lent the writer by the State Geologist, Dr. Joseph Hyde 
Pratt. A hasty examination of thin sections of the . latter rock 
reveals its close resemblance to the Purefoy’s Mill material, the 
main difference between the two being that the feldspars in the 
Gold Hill rock are uniformly larger. 
Griswold 1 defines novaculite as “a fine-grained, gritty, homo- 
geneous, and highly siliceous rock, translucent on thin edges, and 
having a conchoidal or sub-conchoidal fracture.” The Purefoy’s 
Mill rock differs from the Arkansas novaculites in its lower silica 
content, and in containing kaolin and feldspar in abundance. It 
resembles the true novaculites in its general physical character. 
SUMMARY AND CONCLUSIONS AS TO ORIGIN. 
Field evidence shows that the flint-like slate found at Purefoy’s 
Mill is a member of an undoubted sedimentary series, with dis- 
tinct lamination or stratification coinciding in dip with the other 
members of the series. Microscopic study reveals the fact that a 
mechanical sorting and arrangement of the kaolin particles in lay- 
ers took place prior to consolidation. 
Professor Cobb is of the opinion that the rock owes its origin to 
the consolidation of fine volcanic sand sorted by and deposited in 
deep water, or that the sediment may have been derived from the 
(1) Annual Report of the Geological Survey of Arkansas for 1890, vol. 3. 
