C. II. Smyth, Jr. — Corrosion of Quartz. 



283 



Unlike the replacement by pyrite, this corrosion of the 

 quartz seems to be a rather exceptional feature of the rock, as 

 but few good examples have been found. 



The character of the corroded pebbles is essentially the same 

 as that described by Hayes* and by Fuller, f but in both of 

 these latter cases the pebbles appear to have suffered greater 

 loss, while there is a stronger tendency towards a rapid solu- 



tion of the center of the pebble, leaving the margin as a 

 projecting rim. This form is seldom even approximated in 

 the Oneida specimens, but the resemblance to wind-facetted 

 pebbles, noted by Hayes, is sometimes quite pronounced. 



Hayes explains the corrosion as due to the action of the azo- 

 humic acids of decaying organic matter, combined with potash 

 derived from forest fires, and regards the process as taking 

 place at the surface. 



Fuller concludes that the quartz is dissolved by organic acids 

 supplied by plants buried in the rock when it was deposited, 



*Bull. Geol. Soc. Am., viii, pp. 213-226. 

 f Jour. Geol., x, pp. 815-821. 



