Chap. 7] 



GRAVITATIONAL METHODS 



77 



Table 10 illustrates the effect on density produced by a water content 

 of 50 per cent in the more important types of rocks. ^^ 



Table 11 shows the difference between dry and wet volume weight (bulk 

 density and natural density) based on actual determinations.^^ 



C. Tabulations of Mineral and Rock Densities 



Tables 12 through 18, based on the work of many investigators, largely 

 Reich, show density values for (1) minerals, and (2) rocks and formations. 

 They are divided into groups of metallic minerals, nonmetallic minerals, 

 combustible minerals, rock-forming minerals, intrusive and extrusive ig- 

 neous rocks, volcanic glasses, metamorphics, and sedimentary rocks. 



Table 12 

 DENSITIES OF METALLIC MINERALS 



" After J. Barren, Journal of Geology, 22, 214 (1914). 

 " After H. Reich, op. cit., p. 13. 

 " lUd. 



