Geographij of Ohio 143 



BUILDING STONES 



Not all rock, not even all that appears durable when first quar- 

 ried, makes a suitable building stone. Neither is it true that for 

 building purposes the best stone is always used. Quite as import- 

 ant a factor as durability, ease of working and appearance, is the 

 convenience of getting stone to market. Many important quarries 

 have been put out of business by the opening of others which 

 were more available. In building stone production, Ohio has 

 maintained an important position for many decades. Stone from 

 its quarries has been shipped to all of the central Atlantic states, 

 as well as into the Mississippi basin states. 



Important properties. A stone must be strong enough to sustain 

 the weight to which it is subject in a building. This property is 

 termed ''crushing strength," which refers to the number of pounds 

 pressure per square inch required to break the stone. Few stones, 

 however, have been found unequal to any ordinary weight which 

 they would be called upon to sustain in regular building processes. 

 Even a structure like the Washington Monument imposes on the 

 stone of its base a weight of only a little above six thousand pounds 

 per square inch. The crushing strength of average sandstone runs 

 from six thousand to thirteen thousand pounds. The finer grained 

 limestones frequently have a much higher crushing strength. 

 In reference to this property, the highest grade stones are the gran- 

 ites and crystalline igneous rocks of which we have no quarries. 



For many purposes, it is very necessary that a stone be hard, or 

 else become hard when exposed in buildings. Certain sandstones 

 may be crumbled even with the fingers. The particles of sand, 

 being quartz, are themselves very hard, but the ''hardness" of a 

 clastic rock depends upon the manner in which its components 

 are cemented together. It is quite immaterial how hard the indi- 

 vidual particles are, unless the}^ are firmh^ knit together the stone 

 will not be hard. The usual cements are lime, silica, and iron. 

 The more common cement of sandstone is silica; sometimes, 

 however, we find both iron and lime. In many sandstones, a 

 trace of iron tends to discolor the stone. 



While a stone may be hard, because its particles are closely 

 cemented, at the same time it may be coarse-grained or fine- 

 grained, depending upon its "texture." Furthermore a rock 

 stratum may vary in texture, thus making it uneven. An even 



