116 BÄCKSTRÖM, VESTANÅFÄLTET. 



The constituting minerals are quartz, microcline, orthoclase, oligoclase, brown mica 

 with a little chlorite, iron ore, titanite, allanite, and often epidote, muscovite, sometimes 

 calcite and fluorite. 



Large table-formed microcline crystals, simple carlsbad twins, are a characteristic 

 feature of the fine-grained gråriité (as well as of the »Jemshög»-granite). These microcline 

 crystals give the granite a pofphyritic habit, which is really only pseudoporphyritic, since 

 they are younger than the mica, oligoclase and orthoclase and not phenocrysts of a first 

 generation. — A detailed analysis of the structure of the fine-grained granite — with 

 which the »Jemshög»-granite agrees — is given on the freshest and least pressed material 

 at hand, a granite from 2 km. NE of the southern end of Lake Örlunden. A study of 

 the bonndary between microcline and quartz shows that it is an irregularly curving line. 

 The two minerals send rounded projections into one another. In Fig. 1 is shown an 

 example; here a little area of microcline occurs in the quartz, with the same orientation 

 as the large grain, of which it is no doubt a part. Similarly, small quartzes are seen 

 isolated in the microcline (Fig. 2.) with the same orientation as the adjoining large quartz 

 grains, and not to be confounded with the inclusions of older quartz grains in felspars, 

 exemplified by Fig. 4. — This extremely irregular form of the microcline is probably not 

 due to a contemporary crystallization of microcline and quartz, but is rather the result 

 of some corrosion process; or at least one can say forms like the microclines could have 

 resulted from previous corrosion. 



The form of the oligoclase and the orthoclase against the quartz is also a »corro- 

 sion-form» with the same irregularly curving bonndary between the minerals. The ex- 

 ample, Fig. 3, shows also in the orthoclase one small quartz grain seemingly isolated but 

 -with the optical orientation of the quartz outside. — Against microcline, orthoclase and 

 oligoclase show themselves to be older, but are seldom idiomorphic, the boundary is fre- 

 quently irregular and not smooth as against quartz but indented by newly deposited 

 felspar. 



The structural phenomena exhibited by these (and many other) granites recall the 

 descriptions by the French petrographers of the »deux temps de consolidation» to be seen 

 in granites: — »1'examen attentif de tout granite permet d'y découvrir des cristaux plus 

 anciens, en partie brisés ou corrodés, apatite, zircon, sphéne, biotite, bisilicates, oligoclase, 

 orthose, et une derniére poussée cristalline servant cle ciment aux elements précédents et 

 généralement composée d'orthosé et de quartz, parfois associés ä la muscovite». f — It 

 may well be doubted whether a contrast between an older and a younger generation or 

 »consolidation» may be recognized in every granite. Especially in the fresh, entirely un- 

 crushed granites of the younger formations such a contrast could hardly be proved. — In 

 the granites here studied the »corrosion-form» of the microcline is as evident as that of 

 the older felspars. This we could not explain without dividing the »derniére poussée» of 

 microcline and quartz into two, the last cpmprising the chief part of the quartz. The 

 writer considers the differenees from the hypidiomorphic structure in these granites as 



Michel Levy, Granite de Flamanville p. 17 (Bull. des services de la cavte géol. de France, N:r 26, 

 >3), 



