QUARTZITE. 8 BY 



parts of water." The openings between sand grains are of capillary size. 

 The circulation of the sea water through sandstone formations below the 

 sea where there is hydrostatic equilibrium must be exceediug-ly slow; 

 indeed, is probably negligible. In the case of sandstones there is no way 

 by which recrystallization may cement the material, as with the psephites, 

 which contain minerals capable of expansion reactions. The sand g-rains 

 are composed of quartz, and quartz is required for cementation. There is 

 no belt of weathering-, the material of which is being continuously dissolved 

 and transported to the belt of cementation below. For the above reasons 

 it is thought that the cementation of sandstones, while still below the waters 

 in which they were deposited, is negligible. If this be true, the cementation 

 of sands must take place after they have been raised above the sea and an 

 underground circulation has been established. Even after these conditions 

 exist, and the conditions are favorable to a vig-orous underground circula- 

 tion which steadily derives from the belt of weathering large quantities of 

 silica, cementation is still very slow. 



It has been seen that the amount of silica required to indurate the 

 great quartzite formations is enormous. The vastness of the geological 

 work of this kind probably gives us the best measure of the extent to which 

 ground waters have circulated and the enormous amount of water which 

 must have passed through these formations before the cementation is 

 complete. 



The numerous analyses of mineral spring waters, more than ordinarily 

 rich in soluble compounds, show that such waters do not contain, on the 

 average, more than one part by weight of silica in 100,000 to one part in 

 10,000. This latter amount is exceeded by only a few wells or springs, 

 such as the Humboldt salt well/ Supposing that the underground water 

 which passes into the belt of cementation steadily carries one part in 50,000 

 of silica by weight, and that all of it is deposited, the filling of a pore space 

 amounting to one cubic kilometer would require the circulation of 50,000 

 times. 2.6, or 130,000, cubic kilometers of water. 



Even for the cementation of a single formation, such as that of the 

 quartzite of the Penokee-Gogebic iron-bearing district of Michigan and 



a Murray, John, and Renard, A. F., Deep-sea deposits: Report on the scientific results of the 

 voyage of H. M. S. Challenger, 1873-1876, London, 1891, pp. 286-288. 



&Peale, A. C, Lists and analyses of the mineral springs of the United States: Bull. TJ. S. Geol. 

 Survey, No. 32, 1886, p. 159. 



