312 0. H. Smyth, Jr. — Pseudomorphs from New York. 



form might be derived from either one of the minerals 

 involved. 



Among the large variety of pseudomorphs after scapolite, 

 mica holds an important place, and many instances of its occur- 

 rence have been described, particularly in Europe. Neverthe- 

 less, as so often happens in phenomena of this kind, it is by no 

 means easy to account for the details of the process of altera- 

 tion. The necessary magnesia is readily afforded by the sur- 

 rounding limestone ; indeed, magnesian pseudomorphs, notably 

 talc and serpentine, are abundant throughout the limestone 

 belts of Northern New York. But the sources of the iron, 

 potash and fluorine, together with the precise nature of the 

 chemical reactions involved, remain a matter of great uncer- 

 tainty. 



In connection with this alteration of scapolite, two specimens 

 of the same mineral in the Root collection of Hamilton Col- 

 lege are of interest. On one of these, from Edwards, minute 

 crystals of pale yellowish-green epidote partially coat the sur- 

 face of, and penetrate cracks in, the stout light-gray crystals of 

 scapolite. While this cannot be classed as a clear case of pseu- 

 domorphism, it can hardly be questioned that the epidote has 

 grown at the expense of the scapolite, and would have entirely 

 replaced the latter mineral had the process not been checked 

 by changing conditions. 



As is the case with mica, epidote is a not uncommon pseudo- 

 morph after scapolite, occurring in a number of European 

 localities.* 



The second specimen, above referred to, comes from Pierre- 

 pont, and consists of more slender crystals of scapolite asso- 

 ciated with dark-green pyroxene. Some of the scapolite crys- 

 tals are coated with a thin layer of garnet, and this mineral 

 penetrates the scapolite in sinuous threads and bands. As in 

 the previous case, the relation between the two minerals can 

 hardly be accidental and is such as to suggest that the garnet 

 has derived a part of its constituents from the scapolite, and 

 might, ultimately, have entirely replaced the latter mineral. 

 The alteration of garnet to scapolite is described by Cathrein,f 

 but the opposite change, above indicated, the writer has not 

 found treated. 



It is unfortunate that the very limited supply of material 

 interferes with a more thorough study of both these latter ex- 

 amples of alteration. 



Hamilton College, Clinton, N. Y., May, 1897. 



* Roth, Allg. Chem. Geol., i, p. 391. 

 f Zeitsehr. f. Krystall., x, p. 438. 



