On the Formation of Pegmatite. 35 



itgebirges." l Credner here expresses very clearly and dis- 

 tinct^ this view with regard to the Saxon occurrences 

 studied by him:- "The mineral matter of our granitic 

 veins is not derived from mineral springs, perhaps hot, 

 rising from the depths, but from a partial decomposition 

 and leaching-out of the neighboring rocks by water which, 

 oozing through them, gradually becomes a mineral solu- 

 tion," etc. Credner' s authority seems both in Germany and 

 elsewhere to have exercised very great influence upon the 

 theories with regard to the ^ene^is of granitic veins ; for 

 example, we tind 1 his explanation adopted by F. Klock- 

 mann, 3 although not without careful reservations. In 

 Sweden it was the view generally held until I opposed it in 

 my lectures at the Hochschule, in Stockholm, in 1883. * 



The incorrectness of this view is, however, very easily 

 proved and with absolute certainty. It is not true, as Cred- 

 ner considered it to be of certain pegmatite veins of the 

 Saxon granulite district, that a certain correspondence can in 

 general be observed between thecomposition of the pegmatite 

 vein itself and that of the wall-rock. On the contrary, this 

 is found only exceptionally, whereas, according to a rule of 

 general applicability, there is a more or less striking corre- 

 spondence between the pegmatite veins and contiguous 

 eruptive masses genetically related to them. When the 

 pegmatite veins, as is very often the case, occur in those 

 eruptive rocks with which they are genetically connected, 

 there is a correspondence between the vein and the wall- 

 rock; otherwise there is generally no such correspondence. 



It is easy to enumerate a number of striking examples. 

 I remember, first, the veins of Hittero, in the south-west 

 corner of Norway, so long celebrated for their richness in 

 interesting accessory minerals (gadolinite, kainosite, orth- 



1 Zeitschr. d. d. geol. Ges. 1875, 27 ; also 34, 500. 



* L. c. p. 218. 



3 "Beitragz. Kenntn. d. granitischen Gesteinedes Riesengebirges," Zeitschr. 

 d. d. geol. Ges. 1882, 34, 373-426. 



4 Compare Geol Foren, Fbrhaudl., 4, 116. May, 1878. " Mr. Tbrnebohm re- 

 marked that in the last twenty years or so hardly a single Swedish geologist has 

 advocated the eruptive origin of pegmatite." See also 0. Torell, 12 Skand. 

 Niturforskermodes Forhandl., p. 262. 



