Professor Blum on Pseudomorphic Minerals. 



vol. lxv., p. 277-8,^ and according to which it is a normal 

 natronite (natron-mesotyp.) 



I lately received several pseudomorphoses from DrKrantz 

 of Bonn, amongst which was a specimen labelled " Spreus- 

 tein nach Beryll und Scapolith von Breveg." I could recog- 

 nise no scapolitic form in the prismatic crystals of the 

 spreustein, whilst, as hexagonal prisms, they appeared iden- 

 tical with the forms of beryl. But as the occurrence of 

 beryl in the zircon syenites of Norway is very far from 

 ascertained; and as Scheerer (op. cit. p. 280) expressly ob- 

 serves that all which he had met with belonged to the apa- 

 tite ; and as, moreover, the origination of spreustein from 

 this mineral appeared to me exceedingly doubtful, I carefully 

 examined the specimens of this substance in my own collec- 

 tion, in hopes that I might perhaps obtain some solution of 

 my doubts. It was not long before I observed in a piece of 

 ore a small hexagonal prism, which superficially had the ap- 

 pearance of spreustein ; but at the end. where a portion was 

 broken off, was perceived to be Elaeolite ; and eleolite ac- 

 cordingly it was, from which the other mineral had borrowed 

 its form. But in order to attain greater certainty upon this 

 point, I imparted my views to Dr Krantz, with a request 

 that he would be good enough again to look through his own 

 specimens, and acquaint me with the result of his observa- 

 tions. The following is an extract from Dr Krantz's answer : 

 — " I have again examined my small collection of pseudo- 

 morphous Spreusteins, and have come to the precise conclu- 

 sion you anticipated, namely, that the hexagonal prisms were 

 formerly not beryl but nepheline (Eloeolite). The small prism 

 which you will herewith receive, and which is adherent to 

 unaltered felspar (Orthoklas), with which it has nothing in 

 common, consists, at the unaltered-looking greenish end, 

 upon trial with the blowpipe, entirely of mesotype ; there is, 

 therefore, nothing more of the original mineral remaining. 

 The other and larger prism still contains at one end pure 

 white nepheline, but farther in the interior Elseolite. It is 

 remarkable that the nepheline appears here of such a pure 

 wlii to colour as it has never been found with anywhere in 

 Norway, The specimen establishes, I think, in a very satis- 



