﻿CHAPTER V 



CHARACTER AND QUALITY OF THE BLUESTONE FOR 

 STRUCTURAL PURPOSES 



Probably no stone marketed in New York State is more exten- 

 sively known than the " Milestone " of the Catskill region. But it 

 is noted particularly for a special purpose, i. e. as flagstone, because 

 of its capacity to part or cleave into thin slabs. These slabs are 

 proven by experience to have remarkable weather resistance and 

 durability. 



Little attention has been given to the question of dimension stone 

 — whether or not such blocks of as high quality as the flags could 

 be obtained and where such quarries could be opened. 



There are several reasons for this situation. In the first place 

 (i) the stone is of a dark color and has a dull appearance so that 

 it is not fancied for the usual expensive structures where large sizes 

 are used, also (2) the quarries are small, shallow, and are worked 

 on a small scale by single individuals or groups of neighbors with 

 few quarrying tools and no transportation facilities for large mate- 

 rial, and in addition (3) considering the work and equipment neces- 

 sary and the demand the flag industry was more profitable. 



Because of the large demands of the Ashokan dam where nearly 

 a million cubic yards of heavy masonry construction are to be used 

 an entirely new situation has developed. It is especially desirable 

 that a rock capable of furnishing heavy dimension blocks should 

 be discovered. The usual slab or flag type is unsuited to a consider- 

 able part of this work. A study of the adjacent region therefore 

 has been made and explorations along certain promising lines have 

 been conducted to sufficient completeness to prove that a suitable 

 stone can be furnished in large quantity. The characteristics of 

 structure and occurrence as shown by this special study are given, 

 together with some of the later exploratory data. 



Physiographic features 1 



All of the rock formations are sedimentary, chiefly sandstones 

 and shales. They lie in alternating beds of variable thickness and 

 are almost horizontal. The total thickness is many hundred feet so 



1 The principal argument of this discussion has been used in a previous 

 article by the writer under the title " Quality of Bluestone in the vicinity 

 of the Ashokan Dam " in the School of Mines Quarterly, v. 29, no. 2. 



117 



