364 THE EEGOLITH 



weathering. Indeed, in the majority of cases the evidence is 

 all to the contrary; they are plainly a result of deep-seated 

 processes going on in the rock masses long before atmospheric 

 action began to manifest itself. (See under llydrometamor- 

 phism, p. 152.) Indeed the conditions prevalent in soil are un- 

 favorable rather than otherwise to the formation of zeolitic com- 

 pounds, and it is more than probable that such traces as there 

 exist are residuals from the breaking down of rock masses in 

 which they had been previously formed. 



It is well to recall here the work of Curt von Eckenbrecher,^ 

 who showed by a series of analyses, in part his own and in part 

 those of Struve, Gmelin, and 6. vom Rath, that in the early 

 stages of the weathering of phonolites there does seemingly result 

 a zeolitic product. The *^^ weathering" in all these cases had, how- 

 ever, gone no farther than the formation of a whitish but still 

 j&rm and intact crust or zone about the unaltered materiaL 

 While the presence of the zeolite (natrolite) was not proven ab- 

 solutely, its formation from so readily altered a mineral as 

 nepheline or sodalite during the preliminary stages of weather- 

 ing, in which hydration is the most important factor, seems emi- 

 nently probable. It should be noted, however, that F. B. 

 Wright,^ in working on what seemed a similar alteration product 

 in tinguaites from Cape Frio, Brazil, was unable by analysis to 

 show it to be other than a hydrated feldspar. 



In this connection it is well to remember that zeolites as a 

 whole are characteristic of basic eruptive rocks, such as have 

 yielded but a proportionately small amount of our soils. Also 

 that the mutual chemical reactions that may go on in a rock 

 mass due to close juxtaposition of the various minerals may 

 largely cease in a soil where the amount of interspace is so enor- 

 mously exaggerated. 



The researches made during the Ghalleng erTSiX-pedition^ showed, 

 it is true, that even at so low temperatures as from 2° to 3"^ C. 

 phillipsite is being formed in the deep-sea muds of the Central 

 Pacific and Indian oceans. But in these cases the mud is the 

 finely comminuted debris from basic eruptive rocks, itself pe- 

 culiarly liable to decay, and containing all the materials neces- 



^Tscbermak's Min. ii. Pet. Mittheilungen, Vol. Ill, 1881. 

 ^Tschermak's Min. u. Pet. Mittheilungen, Yol. 20, 1901, p. 29. 

 *Rep. on the Scientific Besults, 1873-76, Deep-sea Deposits, 1891, pp. 

 400-411. 



