228 F. W. SAEDESOX THE REDSTONE QUARTZITE 



In the quarry certain shallow erosional dejoressions on the surface of 

 the rock overlie patches of sandstone within the flint}' quartzite. The 

 patches are kettle-shajjed, two or more times as deep as wide. Other soft 

 patches extend on either side of joints. The dike just mentioned, hesides 

 being itself altered to clay for 20 feet (as far as it is seen),- is in contact 

 with leached walls. The foot wall for 4 feet is light-colored, becoming 

 then red. The hanging or east wall is soft, sandj', light-colored rock for 

 6 inches nest to the fault line, and then 2 feet of light quartzite are fol- 

 lowed by the normal read. In the near3'-b3' railroad cut the jointing and 

 the leaching of the rock are seen to follow the stratification largely. In 

 texture the cpiartzite consists of crystalline sand grains which are en- 

 larged, either interlocking or with interspaces filled by silica, which may 

 be partly amorjDhous. The sandstone phase has also secondarily enlarged 

 grains, lacking the cement. The sandstone ma}" be the quartzite with 

 the cement redissolved — that is, with the last deposited mineral first re- 

 moved again by leaching. Again : "there seems to have been a cutting 

 down of the original grains and the formation of a cr}^tocrystalline 

 groundmass inclosing scattered and corroded grains of quartz" {10, page 

 22). Hall (place cited) attributes this corrosion of the sand grains to 

 downward circulation of water, though he appears to hold as nearly as 

 was practicable the same view as Irving and Yan Hise regarding the in- 

 duration of the rock, for he says : "The silica thus dissolved and removed 

 has doubtless acted as the indurating material for the im deriving lavers." 

 The evidence of the deeply rotted volcanic dike in the quartzite argues 

 that the leaching of the rock is vastly greater than has been realized here- 

 tofore. The induration also was originally general and deep, and the 

 "sandstone" represents disintegrated rather than non-indurated rock. 



By reason of the leaching and erosion as described, any original minor 

 faults as well as dikes would tend to be concealed at the surface of the 

 exposures. In the soiithern jwrtion of the area, which is the more in- 

 clined and disturbed, the greater leaching and erosion has taken place, so 

 that the lower strata appear there. Very evidently the hill of quartzite 

 stands as it does l)ecause of the extreme resistance which the massive 

 (piartzite offers to erosion and weathering, and the relation of the Court- 

 land quartzite to other rock formations should be interpreted accordingly. 

 Some consideration may be given also to the fact that the lower strata 

 are in part argillaceous, while the higher ones are rather uniformly pure 

 and coarse-grained, becoming peljljle-bearing or conglomeratic in certain 

 of the strata. 



The extension of the Courtland quartzite to the northeastward is indi- 

 cated, as C. \X. Hall says {10, page 23), by boulders strewn in the glacial 



