KONGL. sv. VET. A K \ i » i ■: M i IfiNB il INDLING A i;. BAND 29. N:o 4. 117 



owittg to a sort of corrosion, bu1 secondary nol priraary, due to the begirming of i h<- 

 örushing of the rook and probably also in äome degrcc to the begin ning of decom position, 

 and consequently not the result of circumstances aocompanying bhe original crystallization 

 of the granite magma; 



In limv large a degree recrystallization has taken place in these moderately pressed 

 and comparatively fresh gijanites is shown by the mode of occurrence of the secondary 

 minerals: muscovite, calcite and epidote. A great part of the biotite, the oligoclase, the 

 raicroclihe and the quartz belohgs to the' same period of crystallization as muscovite, epi- 

 Idöte, and calcite, and consequently, il' they are recrystallized, there are great posstbilitiés 

 rör a cliange of structiire in the granite aftér its First crystallization. — in the continuation 

 of this line lies the explanation for the strueturés of many obscure gneisses. 



All the graiiifes éxamihéd are more or less pressed, but the intensity of pressure 

 or (lie amount of crushing varies very niuch and within very short distances. The prö- 

 gress of crushing is deseribed in detail. Of the results attained only one needs to be men- 

 tioned here. North-west of the Lakes Hultasjöarna (northern börder of the map, plate 1) 

 there is a small massive of schistose rocks, differing from the surrounding gneisses. On 

 the north-western börder the rock is still a typical although somewhat crushed granite. 

 Ou the eastern börder the rock is schistose and crushed, but its mineralogical composition 

 is that of the granite, ricJi in microcline and quartz, relatively poor in plagioclase and 

 mica and distinctly different from that of the gneiss, which is richer in plagioclase and 

 ferromagnesian minerals, but poorer in quartz. It is probably its lesser amount of the brittle 

 quartz which causes the gneiss to be less subject to crushing than the granite: its primary 

 strueture is always better preserved than that of adjacent granites. — The rock occurring 

 between the two deseribed granite-varieties is a typical Saxon granulite, with a little 

 muscovite but no other dark mineral, than small crystals of garnet, and with the strue- 

 ture of an intensely crushed q uartz-f elspar rock. In this case it is evident from field- 

 and microscopical relations, that the granulite is a crushed variety of the common fine- 

 grained granite of the district. 



The petrographical examination shows, that the »Dyneboda» gneiss of De Geer is 

 not one homogeneous rock but two genetically different, one gneiss and the other a gra- 

 nulite, quite similar to the one just deseribed. The granulite is completely crushed and 

 recrystallized, and of its minerals only some of the plagioclase grains show effects of pres- 

 sure (Figs. 5 and 6); the other minerals and the rest of the plagioclase häve been recry- 

 stallized. — The chemical composition of a specimen of this granulite, from Kastagropen, 

 west of Lake Bäen, is as follows 



SiOa Ti02 ALOs Fe20s FeO MnO MgO CaO Na 2 K2O H2O Sum. 



Granulite: 75,44 10,99 2,33 0,93 0,47 0,25 1,24 2,72 4,98 1,06 100,41. 



Granite: 73,38 0,20 14,36 0,3i 0,79 0,22 0,46 1,33 2,85 4,98 0,37 99,so. 



For comparison the composition of the granite from the shore of Raslången, 6 km. 

 NE. from the former locality, on the other side of the quartzite band, is given beneath. 

 — The agreement in chemical composition between the granulite and the granite and the 

 fact, that a quite similar granulitic rock occurs north-west of Hultasjöarna as a facies of 



