70 l'KN'ni KSKor.A. M.-.\. Kl. 



stone, (l(t;i(h<(l ^)\ llic l.ihiiicloiitc-i'ock ma,i;iii;i, hiil tlic regular distribution 

 of tin nodules and lin il almost ( cpial size in each band-shapt-d portion ol 

 the rork is very little in ta\oiii- of this supposition. This fjuestic/n must 

 theieloi-c be left open. 



No oli\ ine-rocks wei"e met with in immediate eonneetion with the- 

 eclogite and labi'adorite-roek on Seljenaes, but not tar frf)m this locality 

 such rocks are exposed neai- .Sorpoll. 



As a general summary, it is clear from the a b r) v e ex- 

 amples, that the C) 1 i \' i n e-r o c k, the eclogite and the labradr)rite- 

 rock are in some way geneticall}' connected with one an- 

 othei-. But, while the two first-named rocks are older .segregations in the 

 gneiss, the labradorite-rock no doubt behaves as a rock solidified later than 

 the gneiss-masses. It also shows another mineral development, or another 

 facies, than the eclogite. 



In the case of the eclogites from the Bergen region we shall meet 

 with a similar relation between the labradorite-rocks, the eclogites and the 

 oli\ine-rocks, still more accentuated. All these rocks no doubt have 

 been derixed by a process of differentiation from one and 

 the same magma, but' the details or causes of this process we may at 

 present leave undiscussed. 



Alteration of the Eclogite. 



The Myi'iJifkitc-lihc plciii^ioclasc-diopsidc-syiiiplcctifc foniicd fi'oiii 

 the cliiiopyroixciic. 



The most common posterior change in the eclogites is the breaking 

 up of the eclogite-pyroxene into diopside and plagioclase. 



But eclogites enclosed in the olivine-rocks are entirely free from this 

 kind of alteration. This is what could be expected, as the clino-pyroxene 

 in these is already primarily a diopside, almost devoid of alkalies and 

 alumina. 



In the following we shall make acquaintance with this phenomenon by 

 means of a few examples, beginning from its first appearance. 



In the eclogite from Silden (tig. 4, pi. I) the alteration appears only as 

 extremely narrow dull, as though dusty, boundary zones around the pyroxene 

 grains. Examined with a high power objective this zone is seen to con- 

 tain pigment-like particles. 



The following stage was observed in a coarse-grained eclogite from 

 the island Lille Rodholmen near Har am. The altjered zone is seen 

 to contain thread-like particles arranged at right angles to the boundaries. 



A little farther developed we find the phenomenon in the chloron\elanite- 

 eclogite from Win el ven (analyzed p. 31, hg. 2, pi. II. The altered zones 



