1914—15] Fjeldbygningen mellein Sørfjorden og Samnangerf jorden. 239 



Here as elsewhere in the crystalline schists the minerals of the 

 smallest molecular volume have thus been formed. 



That the serpentines and the soapstones are gonetically in 

 elose connection with one another seem beyond all doubt. The 

 process has been the folio wing: First, olivine and other Mg Fe- 

 silicates, eventually present, have been metamorphosed into serpentine, 

 which, by the presence of carbonic acid, have later on been altered 

 into tale and magnesite. This metamorphism of the serpentines 

 seems to have tåken plaee according to the following form ula: 

 2 H 4 Mg, Si 2 O y -I- 3 C 2 = H 2 Mg 3 Si 4 J2 -f 3 Mg C0 3 + 3 H 2 0. 

 That this process did not occur simultaneously to the serpentinisation 

 of the olivine but not till this was terminated, may be concluded 

 from the fact that as long as remains of olivine are still to be 

 found, tale and magnesite do not as a rule occur in the rock. 

 The chemical difference between the two processes mentioned, is 

 this: by the first one comparatively much water is absorbed, by 

 the latter one some water is emitted, whereas somc carbonic 

 acid is bound. As for the molecular volume, both the new-formed 

 minerals, tale and magnesite, belong to the group of the h- mi- 

 nerals; especially the magnesite shows a great difference between 

 the calculated molecular volume and the real one. 



The chemical composition may be seen from the analyses and 

 from the calculations bascd on the former (pages 135 — 137). The 

 analysis I is of a dark green serpentine with numerous remains of 

 olivine from a domeshaped hill east of Haga (at the road between 

 Haga and Tveit). The analysis II is of a soapstone essentially 

 consisting of tale and serpentine from the occurrence at the high- 

 way between Hisdal and Aadland. 



The Saussurite-Gabbro-Areas at Aldal and Haga. 



(Pages 152—154.) 



These areas have probably once been adjacent. Already 

 at a distance, owing to their dark weathering-colours and their poor 

 vegetation, avc see that we have to do with saussurite-gabbros. As 

 is commonly the case with flaser-gabbros. and as may be seen from 

 figs. 73 and 74, coarse-grained parts interchange with fine-grained 

 ones. Fig. 73 exhibits a normal-grained saussurite-gabbro, a part 



