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scapolite, enclosing roundt'd ci-ystals of brownish \-iolet augitc and greenish 

 brown hornblende, the latter almost opaque from pigmentary inclusions, 

 and frequent euhedral crystals of apatite. The scapolite (wernerite) is gray 

 from minute inclusions, o.oi mm in maximum diameter, showing no polar- 

 izing effect and therefore being probably isotropic. Their réfringence is 

 high, and they may consist of some gai'net mineral. 



The occurrence of scapolite as a primary mineral in normal igneous 

 rocks was described by me in some syenites from Sviatoy Noss, Trans- 

 baikalia'. Considering that the physicochemical conditions must, in solidi- 

 fying magmas, be often nearly alike those at contactmetamorphic processes 

 where scapolites originate, this mineral will probably prove to be rather 

 common in different kinds of igneous rocks whose chemical composition 

 is favourable for the formatioiT of scapolite. 



TJ}c Altcrafiou of the Minerals in the Garnet-labradorite-rock. 



The garnet and pyroxene, in the rocks of the Bergen region, show 

 an alteration interestingly different from what was described from the 

 €clogite of Nordfjord and More. Even with a rather superficial microscopic 

 examination the alteration may be found to be connected with the saus- 

 suritization, often observed in the plagioclase. 



Where the plagioclase has been saussuritized, there the garnet and 

 P3TOxene are alwa3-s surrounded by altered zones, and I could verify an 

 unmistakable correspondence between the degree of saussuritization and the 

 breadth of the seams. 



An advanced stage of this process was studied in a specimen marked 

 ^'Manger field near Bergen". About a half of the rock-mass consists 

 of a plagioclase, changed into a decimillimeter-grained mixture of granular 

 albite (a' <C n of the canada balsam <C_ yO and prisms of zoisite. Crystals 

 of clinopyroxene, a colourless \'ariety, have been changed so far that only 

 a central part, much less than a half of the original grain, has been left 

 intact. In the garnet, on the other hand, alteration has made slow progress 

 and onl\' thin shells of the green minerals surround the large rounded 

 crystals. 



Between this advanced stage of change and the unaltered rock there 

 are all degrees of gradual variation. I have studied a considerable number 

 of thin sections of the labradorite-rocks from M j el dem, Arnevaagen 

 and S. of T u n g e 1 a n d near Bergen, the n o i- 1 h p a r t of 1 1 o 1 s e n i\ 

 Elsfjeld on Hoi sen o, and between Manger and Saebo. A photo- 

 micrograph (fig. 14, pi. Ill) shows a little advanced stage of the alteration. 



At first sight the greenish zones around the garnets show some re- 

 sem.blance to the hornhlendc-kelyphite described earlier, and the zones 



• Op. cit. 



Vid.-Selsk. Skrifter. 1. M.-X. Kl. 1921. No. 8. 



