TESTS OF WISCONSIN BUILDING STONE 535 



SPECIFIC GRAVITY 



The weight of a rock per cubic foot will increase with the 

 specific gravity proper and decrease with the percentage of pore 

 space. As indicated in a previous paper, the average specific 

 gravity of the mineral constituents is taken as the specific 

 gravity proper of the rock. Following this conception the pore 

 spaces are not considered a part of the rock mass. 



Twenty-five determinations of specific gravity were made on 

 samples of granite from fourteen different quarries. The maxi- 

 mum specific gravity obtained was 2.713 and the minimum 

 2.629, while the average of all determinations was 2.655. Tests 

 on twenty-two samples of limestone from eleven different quar- 

 ries gave an average specific gravity of 2.806. The maximum 

 specific gravity was 2.856 and the minimum 2.700. Tests on 

 thirty-two samples of sandstone from sixteen different quarries 

 gave an average specific gravity of 2.618. The maximum spe- 

 cific gravity was 2.660 and the minimum 2.524. 1 



In the case of the sandstone it is to be observed that the 

 iron oxide which constitutes a part of the cement of the brown 

 sandstone is not present in sufficient quantity to appreciably 

 affect the specific gravity. The specific gravity of the granite, 

 however, is influenced appreciably by the abundance of the 

 ferro-magnesium minerals, as exemplified in the case of the 

 Athelstane granite from Amberg, which gave the highest specific 

 gravity test. An admixture of quartzose material naturally 

 lowers the specific gravity of limestone. 



The stone which gave the highest specific gravity was a very 

 compact and finely crystalline dolomite, and it is interesting to 

 note that samples from this same quarry gave the highest crush- 

 ing and transverse strength of any of the limestone or dolomite 

 tested. 



WEIGHT PER CUBIC FOOT 



Determinations of the weight per cubic foot were made for 

 twenty-five samples of granite from fourteen different quarries. 



1 It is thought that this low specific gravity is due to an unknown error in 

 manipulation. 



