74 I'ENTTI ESKOLA. M.-X. Kl. 



unterscheiden sich nach l'arlje, I^jlarisationsfarlje und I )o])pelhrechung so 

 wenig \om Ompha/it, dass sie wahrscheinlich noch /n ihm gerechnet 

 werden iiiCissen." 



Ihc k'r/vphilr. 



The kelyphitic mantles around the crystals f)! garnet, in the eclogites 

 under consideration, iinaiiablv consist of green hornblende. Very numerous 

 specimens do nf)t show any kelyphite whatever, but the pyroxene meets 

 the garnet with peif'ectly shai-p lines. Many specimens, e. g. those of the 

 chloromelanite-eclogite, having zones of diopside-plagioclase-symplectite in 

 its little advanced stages, have nevertheless no kelyphite, but all those in 

 which the symplectite has developed farther, contain kelyphite also. 



The colour ot' the kelyphite-hornblende is intensixely green, except in 

 the segregations in olivine-rocks, in which brownish or almost colourless 

 kelyphite was met with. 



At amphiboliti/ation the kelvphitic zones grow thicker and finally the 

 whole crystals may have altered. 



Actually this is the . most essential process in the amphibolitization. 

 Hornblende cannot originate from the garnet alone nor from the clino- 

 pyroxene alone; there must be an interaction of both. Conformably to this 

 expectation the amphibolitization, in the eclogites, is invariably seen to take 

 source from the kelyphite shells. 



The kelyphite found in the garnet-olivine-rock from Almklovdalen, 

 analogous to the original kelyphite of Schrauf, consists of a zone of fine 

 fibrous brown-coloured mineral which from its extinction angles seems most 

 like some clinoamphibole. Grains of green or brown spinel often are found 

 all around this zone. 



All the kinds of kelyphite are, from the facies theory, good indicators 

 of the posterior facies of the rock, i.e. that facies in which the alteration 

 has taken place. In the eclogites and dunites of Nordfjord and Mere the 

 kelyphite, as a rule, means a first stage of am phiboli tization, but in the 

 garnet-bearing segregations in the labradorite-rock in the Bergen region we 

 shall make acquaintance with g r e e n s c h i s t-k e 1 v p h i t e, composed of chlorite 

 and epidote-minerals. 



The formation of kelyphite in garnet-olivine-rocks from Saxony, Bo- 

 hemia and the Forest region of Lower Austria, studied bv Mrha', is mainly 

 an incipient alteration from the eclogite into the hornfels (gabbro) 

 facies. Mrha gave an unusually correct characteristic of the nature of the 

 alteration which may be quoted in extenso, as being no doubt one of the 

 earliest clear applications of the static view-point in petrologv. 



Josef Mrha, Beiträge zur Kenntniss des Kelyphits. T. M. P. M. 19, 1900, p. 11 i. 



