Washington — Study of the Glaucophane Schists. 41 



Unfortunately he gives no analyses of true glaucophane 

 schists, but it seems worth while quoting the above two 

 analyses of gabbros, which have partially undergone the 

 transformation. Both are composed chiefly of plagioclase and 

 diallage, which has been largely altered to fibrous green horn- 

 blende, with considerable glaucophane in needles. Chlorite 

 and magnetite occur, but no olivine nor serpentine was seen. 

 Lepsius* also describes a blue gray, partially schistose rock, 

 from west of Olimpos in Attica, composed of glaucophane 

 needles lying in a groundmass of quartz and feldspar. A 

 silica determination gave 87'43 per cent, and it is evident that 

 this is a quartz-glaucophane schist, analogous to those of Syra, 

 and, as will be seen later, of the Pacific Coast and elsewhere. 



Croatia. 



In 1887 Dr. Kispaticf described a number of glaucophane 

 schists, which occur chiefly as boulders or pebbles in various 

 streams of Fruska Gora in Croatia. They vary to some extent, 

 but it is of great interest to note that they may all be classed 

 as either epidote-glaucophane schists, to which the majority 

 belong, or as quartz-glaucophane schists, which are represented 

 by only two occurrences. Garnet is sometimes present in 

 abundance, sometimes quite wanting, and mica is rare, even in 

 the more acid group. 



I am indebted to Prof. Posenbusch for one of Kispatic's 

 specimens from the Srnjevacki Potok. It is of very simple 

 composition, being composed chiefly of frayed, pleochroic 

 glaucophane, and colorless or pale yellow epidote, in grains and 

 prismatic crystals. Between these, but in very small amount 

 is a colorless mineral, which occasionally shows multiple twin- 

 ning lamellge, and is referred to plagioclase. There are also 

 rare rutile grains. 



In thin section my specimen corresponds very well with 

 Kispatic's description. The rock is very fine-grained, com- 

 posed of a pale glaucophane, in xenomorphic masses, with 

 abundant grains and stout crystals of colorless or pale yellow 

 epidote. A colorless mineral, apparently a plagioclase, as sug- 

 gested by Kispatic, is rare, in interstitial grains. 



The analysis shows low Si0 2 , and resembles in a general 

 way that of the Kyperusa rock. It differs, however, in having 

 much higher MgO and lower CaO, as well as in the absence of 

 C0 2 . 



*Lepsius, op. cit, p. 104. 



f Kispatic, Jahrb. k. k. geol. Reichsanst., xxxvii, p. 35, 1887. 



