144 Frank Carney 



fine textured rock is easily dressed and lasts longer. Its texture 

 has had much to do in giving the Berea sandstone of many of our 

 quarries so wide a reputation. 



In general, the more durable building stones are those of highest 

 specific gravity or "density." A porous stone naturally is more 

 exposed to the weather. It absorbs moisture which in the winter 

 season freezes and injures the stone. Other things being equal, 

 the best building stone has a fairly high specific gravity. 



Clastic rocks, to which class much of our building stones belong, 

 represent the assembled components of older rocks. Under some 

 conditions, small crystals may be developed in these clastic rocks. 

 Usually, however, they are simply an agglomeration of worn 

 particles of earlier rocks. Since minerals among themselves 

 differ widely in color, it follows that clastic rocks also are vari- 

 colored. Quartz, for example, is sometimes perfectly white, some- 

 times red. Feldspar is often red. ]\Iost of the biotite is dark. As 

 a result, building stones vary in color, from prevailingly dark to 

 buff and white. Sometimes upon exposure the color of the stone 

 changes. This not infrequently occurs with sandstone carrying 

 a small amount of ferruginous matter which oxidizes and gives the 

 stone a rusty appearance. In walls of buildings, one block of 

 such a stone frequently discolors quite a strip below it. 



Liinestone. The earliest building stone quarries in Ohio were 

 opened in limestone horizons. Many of our limestones are admir- 

 ably adapted to structural purposes. The depression of the Scioto 

 valley, and the erosion that has taken place along the axis of the 

 Cincinnati anticline, have combined to expose four ages of lime- 

 stone, each of which has been used extensively for structural 

 work. I will speak briefly of these four horizons, commencing 

 with the earliest. 



Above the Trenton formation, a very hard limestone occurs in 

 the Hudson River group of the lower Silurian. This limestone 

 is found usually in thin beds, quite uniform in thickness. The 

 strata are generally separated by shale layers, which makes quarry- 

 ing easy, but produces large waste piles. This limestone has had 

 extensive local uses, but has never been shipped to very distant 

 points. Its color and its crystalline surface make it desirable; 

 while it is a little more difficult in dressing, at the same time when 

 properly tooled it is a very pretty building stone. Doubtless the 

 demand will increase as shipping facilities improve. 



