CHAPTER III. 
GEOLOGIC AGE AND GEOGRAPHIC DISTRIBUTION OF 
THE CLAYS. 
CONDITIONS GOVERNING DISTRIBUTION. 
The distribution of clays depends on the distribution of the geo- 
logic formations from which they are derived, and hence on geologic 
structure. From what has been said of the origin of clays it will be 
seen that their distribution throughout the State must necessarily 
depend on the State's geologic history, or the manner and order in 
which the rocks have been made and unmade. Where we have the 
crystalline rocks, which yield kaolin on decay, there we may look for 
kaolins, and in order to look intelligently we must know the distri- 
bution of those particular rocks. The clay shales we can expect to 
find only in association with the Paleozoic rocks, and as they are 
abundant in the rocks of the Carboniferous system we must ascertain 
the distribution of the rocks of that age. The Tertiary and Creta- 
ceous clays can be found only with the Tertiary and Cretaceous rocks, 
and in searching for them it is essential to know the areas of these 
rocks in the State, the position in which they lie, the character of the 
various beds, and the places the clays occupy in the series. 
These instances are cited for the purpose of showing how indis- 
pensable to an intelligent search for clays is a knowledge of geologic 
structure and the areal distribution of the various geologic forma- 
tions. A geologic map of the State (PI. I) is inserted in this report 
for the purpose of furnishing this information. 
PALEOZOIC CLAYS AND SHALES. 
The clays of the Paleozoic areas of the State consist of shales of 
Paleozoic age found in place, and of alluvial or other clays of recent 
age spread over the lowlands. The clays of the latter class are 
derived indirectly from the Paleozoic rocks of the surrounding regions 
and may form brick earths or pottery clays. 
When clays are subjected to a great pressure for a long time they 
become hard and stonelike, forming what are known as shales and 
slates. Nearly all of the clays of Paleozoic age have been crushed 
under pressure so great and for so long a time that they have become 
thus hardened into shales. 
The clay shales which were derived from the wear and decay of other 
rocks were originally deposited in horizontal beds in the water of the 
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