On the Formation of Pegmatite. 63 



theories which hold the presence ot albite as proof of 

 aqueous origin must fall to the ground. l 



It has been sufficiently dwelt upon above that all the 

 minerals of the pegmatite veins (even all the albite) have 

 not necessarily been formed by crystallization from a 

 magma. \ 



2. In their geological occurrence the pegmatite views are 

 similar to other eruptive veins; they traverse all sorts of 

 rocks, contain fragments of the same, etc. Examples of 

 the first statement have already been cited, the presence of, 

 foreign fragments in pegmatite veins is so common that it 

 is quite unnecessary to cite special cases. It can hardly 

 be superfluous, however, to state explicitly that both in 

 acid granite pegmatite veins (several of the veins in the 

 neighborhood of Arendal) and in nepheline syenite peg- 

 matite veins (southern point of Stoko) I have observed 

 foreign fragments of the wall-rock exhibiting an arrange- 

 ment relative to one another such as is possible only in the 

 case of a rock formed from an eruptive magma. 



The extremely intimate relations of pegmatite veins to 

 veins formed in a different manner but of corresponding 

 composition and of undoubted eruptive origin are also of 

 weight in this connection ; the gradual passage of the ne- 

 pheline syenitic pegmatite veins of the boundary zone on 

 the Langesund fjord into the normal-grained nepheline 

 syenite veinstones of the same locality has been amply 

 described above; in the case of ordinary acid granitic peg- 

 matite veins this phenomenon is well known, and has been 

 frequently and deservedly referred to by prominent petro- 

 graphers. 2 The same thing is also true of granite types 



1 See further : Alfred Gerhard, " Beitrag zur Kenntniss d. sogen. Soda- 

 granite," Neues Jahrb. f. Min. 1887, 2, 267-275 ; he found as principal component 

 of the vein-form granite of Ulfserud, Sweden, an almost pure albite, with micro- 

 cline, quartz, biotite and muscovite, zircon, apatite. Significantly this granite 

 rich in albite was a vein granite ! 



2 Michel-Levy (Struct, et class, d. roches erupt, p. 15) remarks, for instance, 

 " notre structure pegmatoide (pegmatite graphique a grands elements) dont nous 

 atfirmons la liaison intime tant avec les granulites massives qu' avec les granu 

 litesen filons (aplites)," <fcc See also the excellent and instructive remarks of J. 

 Lehmann, 1. c. p. 26 : " It is not admissible to separate the half pegmatitic, half 

 granular vein formations and the smaller veins of purely granular structure from 



