Washington- — Study of the Glaucophane Schists. 57 



to a more basic group of gabbros, also occurring in Attica, 

 which furnish serpentine on alteration.* 



The Attic Cretaceous shales, according to Lepsins,f also 

 yield glaucophane schists as products of metamorphism. 

 Unfortunately no analyses are given, but some of them, as 

 that from Yelaturi near Thoriko, must resemble closely the 

 Kyperusa schist, being composed essentially of glaucophane 

 and epidote. Others again are more acid and carry along with 

 glaucophane abundant quartz, feldspar and white mica. 



In this connection it is of interest to note that glaucophane 

 schists are very common in the whole region of metamorphic 

 rocks which runs along the eastern coast of Greece, and extends 

 southward and eastward through the Archipelago. Rocks of 

 this character have been described from Thessaly,J Enboea,§ 

 Attica,|| Thermia,! Tinos,** Siphnos,ff Syra, Milos,jf 

 Samos,§§ Rhodes,! I and Smyrna.^ 



We have already seen that the glaucophane schists of 

 Anglesey are probably derived from diorite (possibly gabbro), 

 since, according to Blake and Harker, gradual transitions are 

 observed from massive diorite to hornblende schist, the glau- 

 cophane schist being locally developed. Serpentine also occurs 

 on Anglesey, though not near the Monument, where diorite 

 occurs.*** Though the whole district has been subject to 

 regional metamorphism,ttf it is uncertain whether the develop- 

 ment of glaucophane schist is due to this or to contact meta- 

 morphism. 



Another instance of derivation from basic igneous material 

 is that given by Rosenbusch in the paper already cited. He 

 describes specimens sent by Palache, labelled " altered tuff " 

 from near Berkeley, Cal., and concludes that these diabase 

 tuffs do in fact alter to true glaucophane schists. 



In his monograph on the Quicksilver Deposits of the Pacific 

 Slope Becker^JJ briefly describes the alteration of diabase to 

 glaucophane schist, and also speaks of the glaucophane schists 

 of Mt. Diablo passing over into slightly altered shales. 



* Lepsius, op. cit., p. 86. 



f Lepsius, op. cit , pp. 133 and 136 ff. 



X F. Becke, Min. Petr., Mitth., vol. ii, p. 49, 1879. 



§ F. Becke, op. cit., p. 71. 



j| Lepsius, op. cit. 



^[Oebekke, Zeitschr. d. d. Geol. Ges., vol. xxxviii, p. 644, 1886. 



**Von Eoullon aud Goldschniidt, op. cit. pp. 24 and 31. 



f+K Ehrenburg. Iuselgruppe von Milos. Leipzig, 1889, p. 101. 



it I. Cheluesi, Giorn. di Min., vol. iv, p. 34, 1893. 



§§ Foullon, Sitzber. Akad. Wiss. Wien, vol. c, p. 176, 1891. 



||j|Oebokke, op. cit.. p. 651. 



*** Cf. Blake, Q. J. G. S., vol. xliv, pi. xiii, 1888. 



•HfSir A . Geikie, Anc. Vole, of Gr. Brit, vol. i, pp. 128, 220, 1897. 



XXX Becker, op. cit, pp. 100 and 102. 



