I'F.NTTI F.SKOI.A. M.-N. Kl. 



an cnstatitc-rock lixe from olivine. The cnstatitc occur.s in the form oi' 

 coarse pri.sm.s, one or two centinietei's long. 



Py 1"'^^ pofl i " P ^ i ti e-f) 1 i V i 11 e-r o c k is found at a few points in the 

 central parts f)\' the larger masses of ckinite, where eclogitic segregations 

 also occur. The rounded crystals of red pyi'ope, about 0.5 cm in average 

 (liaiiictci- and surrounded by a kdy phite-shell, and equant cry.stals of 

 emerald-green c h r o 111 e-d i o ps i d e of the same si/e are evenly scattered 

 in the much Hner ground-mass of olivine, and in addition occur some 

 crystals of enstatite. 



In a specimen of pyrope-diopside-oli\"ine-iT)rk from Lien I determined 

 some optical constants of the minerals. 



Olivine: ^ ^ - i .670 + 0.00 1 . 2\' y ^^ 85 appr. 



Composition: Fo,,„Faj^„. 



P y rope: n 1-742 + 0.002. 



Composition: FcjoMgj-^Caj.,. 



Ch rome-d i ops ide : ^ ^^ 1.678 ± 0.002. 



Composition probably nearly identical with the pyroxene from the 



eclogite of Almklo\dalen (cf. analysis p. 28), though with more 



chromic oxide. 



Enstatite: y ^^ ^ .670 ± 0.002. 



Composition apparently nearly identical with that of the enstatite 



from Almkloxdalen with 5.20 ^ ü FeO in which K. Johansson ' 



detei'mined 



«Na=" 1-6607; ^Na "= I-6658; y^.^, - I-6715. 



2Vy - 76' 54'- 



All these varieties of dunite and saxonite are very constant types of 

 rocks, and in various occurrences in many lands their minerals show the 

 same characters and ha\e the same composition. But in the absence of 

 every trace of serpentinization the best preserved dunite in Almklo\dalen 

 is almost unique in the whole world. 



As Reusch points out (loc. cit. 1877), serpentinization occurs in 

 the occurrences in Almklo\'dalen mainly near the boundaries of the masses. 

 The same writer proved by microscopic examination and comparison with 

 surface-specimens exposed to the atmospheric agencies, that this alteration 

 has nothing to do with the weathering. P'rom the faciès theory it is ap- 

 parently a posterior change impressed upon the rock on its way towards 

 the earth's surface. Its character tells us about the conditions of the 

 greenschist faciès. 



' K. Johansson, Bihans till K. Vet. .\kad. handl. Stockholm 17. X:o 4, 1891. Ret", in Zs. 

 Kr. 23, 152. 



