BUILDING AND ORNAMENTAL STONES. 445 



theory that the quarry water holds in solution certain of the cementing 

 materials, as has been already noted (p. 339). 



(b) Varieties of Sandstones. 



Many varieties of sandstones are popularly recognized, the distinc- 

 tions being founded upon their composition, structure, the character of 

 the cementing material, or their working qualities. Arkose is a sand- 

 stone composed of disintegrated granite. Ferruginous, siliceous, and 

 calcareous sandstones are those in which these substances form the ce- 

 menting material. Argillaceous sandstones contain clay, which can 

 easily be recognized by its odor when breathed upon. Flagstone is a 

 sandstone that splits readily into thin sheets suitable for flagging ; the 

 same term is applied to other rocks, as the schists and slates, which 

 serve a similar purpose. Freestones are so called because they work 

 freely in any direction, their bedding or grain not being strongly enough 

 marked to in any way interfere with this property. Graywacke is a com- 

 pact sandstone composed of rounded grains or fragments of quartz, 

 feldspar, slate, and other minerals, cemented by an argillaceous, calca- 

 reous, or feldspathic paste. This term is no longer in general use. 

 Quartzitcs result from the induration of sandstones, a result brought 

 about either by pressure or, more commonly, by the deposition of silica 

 between the granules. 



Sandstones occur among rocks of all ages, from the Archaean down to 

 the most recent ; none are, however, at present used to any great extent 

 for building purposes in this country that are of later origin than Trias- 

 sic, or possibly Cretaceous. In the list of natural building materials 

 of the United States sandstone ranks third in importance ; the census 

 returns for 18S0 showing a product of 24,770,930 cubic feet, valued at 

 $4,780,391. 



(c) Sandstones op the Various States and Territories. 



Alabama. — On the line of the Alabama Great Southern Eailway, some 

 60 or 100 miles from Chattanooga, Tenu., there occurs a yellow sand- 

 stone that is sufficiently soft when first quarried to be cut with an ax, 

 and which hardens sufficiently on exposure to be very durable in that 

 climate. Samples of this stone received from De Kalb County are of 

 decidedly inferior quality. 



Arizona. — There is at present little demand for building stone in this 

 Territory, and consequently but little is known regarding its available 

 material. From Yavapai County, on the line of the Atlantic and Pa- 

 cific Eailroad, we have received a block (No. 35571) of fine grained, com- 

 pact, light-pink sandstone, that from its warm and pleasing color and 

 easy working qualities would be eagerly sought by Eastern builders 

 were it more accessible. So far as we are informed, it is not at present 

 quarried to any extent. 



Arkansas. — Brown massive " freestone " that will make a good build- 

 ing stone is stated by Owen* to occur in Van Buren County. 



"Geol. of Arkansas, 1858, p. 75. 



