THE TERRESTRIAL PERIDOTITES. — LHERZOLITE. 145 



almost exclusively of the latter mineral. According to the nomenclature of Brogger, the 

 rock of these patches sliould he called olivine schist. By alteration it gives rise to ser- 

 pentine with the characteristic reticulated structure which ever marks the serpentine de- 

 rived from olivine.* Occasionally the fibrous serpentine forms veins of considerable size 

 in the adjacent rocks. The olivine schist when purest has no schistose structure. The 

 passage from pure talc schist in which no olivine occurs to that composed almost completely 

 of olivine, takes place sometimes within a short distance. The chief mass of the rock, how- 

 ever, is a middle stage between the two extremes, having a distinct schistose structure and 

 composed for the most part of olivine and talc, besides considei'able quantities of pyroxene 

 as well as other minerals not yet determined." 



Differing in some points from Mr. Diller, although agreeing with him in the main, it 

 has seemed best to add more special descriptions of the individual rocks and sections in 

 question. It is furtlier necessary to do this iu order to point to the gradations and altera- 

 tions which are conspicuous in them. Part appear to belong to the Iherzolite variety, 

 while others are so far altered that it cannot be predicated what was their original com- 

 position as a whole. 



A. E. 324, from Mitylene, is a greenish-black compact rock containing lighter green 

 crystals of enstatite. The section shows a grayish-brown groundmass, holding crystals 

 of enstatite and diallage. This groundmass is formed by a network of grayish-brown 

 serpentine, holding olivine, en.statite, diallage, and iron ore. Much of tlie enstatite is 

 altered to a grayish-brown fibrous serpentine, but some portions remain intact in part 

 of the crystals, while other crystals are entirely unaffected. The diallage is abundant, 

 but in small irregular grains and imperfect crystals. Part of this appears to be an 

 augite-diallage, for it has well developed both the prismatic cleavage of augite and 

 the orthopinacoidal cleavage of diallage, as well as traces of a clinopinacoidal cleavage. 

 Elongated dashes of iron ore are occasionally arranged parallel to 010, forming with 

 the well-developed cleavage parallel to 100 a rectangular grating. Part of the iron 

 ore is secondary, occurring in grains arranged in the centre of the serpentine veins, 

 but part appears to be the product of alteration of picotite, since the interior portion 

 still is of a translucent reddish-brown color. From its general characters the ore is 

 probably chromite with some magnetite. 



A. E. 208, from Qarii-dagh, is of a similar character, but has less enstatite and diallage, 

 and more olivine. In some places the olivine has suffered almost no alteration, while in 

 others the change is complete. The rock is corajjact, greenish-black, containing light- 

 greenish enstatite crystals, and coated with a greenish " slickenside " of serpentine. 



A. E. 209, from near Mt. DayJah by the Plain of Troy, is a grayish-green rock hold- 

 ing enstatite crystals altered into a talcose-like material (bastite) and presenting a 

 greenish to silvery-white appearance. The section is similar to the preceding, but more 

 highly altered, the serpentine predominating. The diallage is abundant, and in its 

 structure closely resembles that of the meteorites, being composed of a series of granules 

 aggregated together into larger masses, and separated by little patches of different 

 material. 



A. E. 481, from the southeast part of the Chiplak, Mt. Ida, is a dark-green rock 

 weathering brown and containing talc scales and grains, and bands of chromite. The 

 section is grayish, and presents a schi.stose appearance, owing to the arrangement of 

 its ii'on ore, etc. It is composed principally of a serpentine network enclosing olivine. 

 A little enstatite and diallage were observed, also iron ore and secondary talc. 



* With tliis statement of Mr. Diller the pi-csent writer is unable to agree. 



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