On the Formation of Pegmatite. 37 



veins at Luchon, which rise through mica schist and super- 

 imposed ''schistes noirs carburet ou pyriteux," etc. An 

 example, instar omnium, is the occurrence of akmite granite 

 pegmatite at Rundemyr, on the Eker, already mentioned 

 and described by me, in Silurian schists and limestones, 

 about a kilometer from the boundary of the adjacent aegirine 

 granite district of Kyrfjeld-Hamrefjeld, etc. This last ex- 

 ample, so absolutely different to all the others, is of all the 

 more interest, as it further invalidates the old erroneous 

 idea that pegmatite veins never occur in the younger sedi- 

 mentary rocks. 1 Further, the syenitic pegmatite veins 

 occurring in augite porphyry to about one-half a kilometer 

 away from the boundary of the augite syenite of Ramsas, 

 west of Birkedalen, might also be introduced as an example 

 of the fact that the composition of the pegmatite veins is 

 independent of that of the wall- rock. 



That these last-mentioned veins, as also those occurring 

 in the Devonian sandstone of the boundary zone on the 

 Langesundfjord, have, on account of resorption from the 

 wall-rock, a composition somewhat different to that of the 

 veins occurring in the augite syenite, does not alter the main 

 result. Perhaps the connection between wall-rock and 

 vein-material, which Creclner records among his observations 

 in the Saxony granulite district, may to some small extent 

 be explained in a similar way; to a certain extent, veins 

 formed in various ways seem to have been treated in 

 Credner's description from a common point of view. 



The above mentioned examples, particularly the ordinary 

 acid granitic pegmatite veins in the basic labradoiite and 

 norite rock of Hittero, and the aegirine granite pegmatite 

 vein of Rudemyr in Silurian limestones and schists, demon- 

 strate conclusively that Credner's opinion with regard to 

 the formation of true pegmatite veins, by a leaching-out of 

 the wall -rocks through the agency of percolating water at 



1 See e. g. A. v. Groddeck, " Ueber Tourmalin enthaltende Kupfererze," etc., 

 Zeitschrift d. d. geol. Ges., 1887, 39, 256: "First of all, granitic veins (peg- 

 matite, graphic-granite) must be mentioned ; these occur exclusively in eruptive 

 (granite) and archaic rocks, and never break through younger sedimentary 

 rocks." 



