66 Canadian Record of Science. 



banded or zone-form arrangement of the vein material. 

 This however is never laminated, as in the case of mineral 

 veins deposited from genuine aqueous solution, l but only 

 indistinctly zonal inasmuch as the outer zones pass con- 

 tinuously into the inner. 2 The zonal structure, when any 

 such is present, which however is generally not the case, 

 usually makes itself evident only in a finer-grained condition 

 of the vein boundaries, and sometimes (especially in the 

 case of granitic pegmatite veins) in a zone with graphic 

 structure next the fine-grained eugranitic marginal zone, 

 upon which there frequently follows (especially in acid 

 granitic pegmatite veins) in the middle of the vein a 

 tremendous size of grain, here often with special enrich- 

 ment in rarer minerals and (also particularly in acid veins) 

 not seldom with open or distinctly drusy cavities filled with 

 peculiar mineral deposits. 



Thus, this " zonal," band-form, etc., structure, as it oc- 

 curs in genuine pegmatitic veins, may without any great 

 difficulty be accounted for through magmatic crystalliza- 

 tion. 3 Finer grained structure along the sides of the veins 

 is in general characteristic of eruptive veins, the graphic 

 structure is explainable only through magmatic crystalliza- 

 tion, and the drusy structure of the middle of the vein, 

 which however is frequently wanting, 4 may be explained 

 as quite in accordance with the formation of miarolytic 

 drusy cavities in normal grained eugranitic rocks. More- 

 over, it must again be remarked, that the minerals which 

 have crystallized out in the drusy cavities have in part fre- 

 quently had a different mode of formation to those of the 



1 Compare also Gr. Vom Rath, 1. c. p. 649. " It reminds one of the almost sym- 

 metrical grouping of the minerals of certain ore veins. Nevertheless the two 

 phenomena are quite distinct." 



2 I must distinctly remark, that I here leave out of the question a part of the 

 " granitic" veins described by II. Credner in his treatise ; in this treatise certain 

 mineral deposits belonging to ' regional metamorphism' are evidently treated 

 from the same point of view as true pegmatitic vein formations. To enter here 

 more into detail would lead too far. 



3 Compare also J. Lehmann, Granulitgebirge, &c, p. 46. " A zonal structure 

 of our granitic veins has in it nothing exceptional and speaks neither for nor 

 against formation by injection." 



4 In the veins of the Annerod Peninsula this is very rare. 



