the Zeolite Family. 267 



to occur. The lime may be viewed as replaced in Ardrwedson's 

 Scottish mineral by soda. 

 The formula for chabasite given in the paper of Berzelius 



containing the analyses of the mineral, is N >- .S'^-f-3 AS^ +6 A//; 



the first bracket expressing the replacements of the lime, pot- 



assa and soda. In the last published collection, however, of his 



jij» "I ... 



formulae *, that for chabasie is thus framed, ^3 f S' + 3A/ Si^ 



-I- 18 H, which corresponds with the more simple formula of 



^1 S^ + 3AS* + 6Agr. But as there is little doubt that 



the lime chabasites, are much more common than the soda cha- 

 basites ; it seems, with every possible deference for so great a 

 name as that of Berzelius, objectionable to adopt a formula, in 

 which the most ordinary of the three replacing ingredients is 

 omitted. Indeed a doubt may be reasonably expressed, whe- 

 ther the mineral analysed by Ardfwedson, was really a chabasite. 

 I have examined, in a general way, chabasites from three other 

 localities, besides those already mentioned, namely, one from 

 Ireland, another from the Island of Skye, and a third from Ice- 

 land ; and, in all of them, lime was found to be a pretty abun- 

 dant ingredient : and although the nature of the whole of their 

 constituents was not determined, I think there is every reason 

 to believe that they are constituted in a manner very similar to 

 the lime chabasites, already mentioned. Even if we should leave 

 soda entirely out of view as a replacing ingredient in chabasite, 

 it still may be held, that replacement occurs within certain 

 limits between the lime and potassa ; as these ingredients will 

 be found to vary somewhat in proportion in the above men- 

 tioned analyses, the one increasing, as the other diminishes. 



In the whole circumstances, the formula of K >• S* -|- 3 A S* 



^ 



-f- 6 A9, is perhaps the best calculated to express the general 

 composition of the mineral. 



* Poggend. Annalen, xii 



