144 PERIDOTITE. 



my cluirgo. Mr. Diller (wlio collected the specimens) has kiudly consented that I should 

 use his written description of the Assos serpentine rocks, not yet published except in ab- 

 stract,* and it is given below, with a few verbal changes to adapt it to the present work. 



"Serpentine occurs in the Troad at Qara-dagli . . . derived from the alteration of 

 eruptive rocks; also about the summit of Mt. Ida in small lenticular masses in talcose 

 schist, and belongs to the stratified rocks ; also . . . forming low rounded conical hills 

 near the base of Qara-dagh. The rock is usually of a deep green color, but varies, 

 becoming bluish or reddish, often presenting smooth fibrous surfaces like slickensides, 

 and occasionally an imperfect columnar structure. Althougli locally uniform, it is gen- 

 erall}^ made porpliyritic by a fibrous or lamellar mineral, whose cleavage plates between 

 crossed nicols show an acute bisectrix with the plane of the optic axes at right angles 

 to the fibrous structure. The mineral is bastite, and in all probability has been produced 

 by the alteration of enstatite. 



" Under the microscope the composition of the rock is seen to vary greatly. Sometimes 

 it is composed almost wholly of a network of serpentine containing a few grains of unal- 

 tered olivine, bastite, and much iron ore. In other cases the serpentine is a subordinate 

 constituent, and olivine forms the chief mass, in which are imbedded enstatite, for the 

 most part changed to bastite, and also very rarely a colorless mineral, with prismatic and 

 pinacoidal cleavage. It appears to belong to the pyroxene group, but with the few sec- 

 tions present its optical relations could not be determined. It is evident that the 

 serpentine of Qara-dagh is derived from an olivine enstatite rock. 



" In the Kemar Valley, a short distance east of where it opens into the Trojan Plain, 

 loose blocks of serpentine containing numerous very bright silvery crystals of bastite have 

 been observed. In the thin section, besides serpentine, olivine, enstatite, bastite, and 

 irregular dark grains, there occur numerous small black crystals whose square rhombic 

 and hexagonal sections indicate that they may belong either to spinel or magnetite ; but 

 as they are not translucent, they are most likely magnetite. 



" Further up the valley the serpentine is indistinctly porpliyritic, and occurs inti- 

 mately associated with schists and crystalline limestone, through which it appears to peue- 

 ti'ate in the form of irregular dikes. Its specific gravity is 2.593. The microscopical 

 structure of these rocks is strongly contrasted with that of the serpentine from Qara- 

 dagh. Between crossed nicols they appear rather coarsely microcrystalline, and through- 

 out the greater portion of the section are not only uniform, but show no trace of the 

 characteristic reticulated structure of serpentine derived from the alteration of olivine.-j* 

 However, here and there a few meslies of the old net are still preserved, and there 

 appears to be a passage from this porti(m into the other, in which the same structure can- 

 not be traced. The porphyritic crystals, as in the other cases, are bastite, with considerable 

 quantities of carbonates. According to Mr. Frank Calvert the serpentines in the vicinity 

 of tiie Kemar Valley occur as distinct dikes cutting the crystalline limestones, so there 

 can be no doubt concerning their eruptive nature, and they are in all probability derived 

 from olivine enstatite rocks. 



" Near the centre of Mt. Ida the oldest rocks crop out, and among them are talcose 

 schists, which by the addition of olivine pass into small lens-shaped masses composed 



* Papers of the AvcliEcological Institute of America, Classical Scries, i. 201, 203 ; Science, 18S3, ii. 

 255-258. 



t Hussak, after studying? microsonpically a number of Alpine serpentines, concliulcd that in the ser- 

 pentines derived from schistose rocks the characteristic reticulated structure, chroniite, and picotitc are 

 wanting. 



