162 PERIDOTITE. 



Strand, Timor. 



Another porodite of similar character was described by Wichmann as a greatly decom- 

 posed fragmental rock, composed of rounded and angular fragnieuts of dirty-brown and 

 brownish-green serpentine, cemented by a sometimes lighter, sometimes darker, dirty- 

 brown and greenish-brown mass. Microscopically this serpentine is similar to the pre- 

 ceding, but is more altered. The interior portion of some of the grains is filled with a 

 dirty-brown hydrated oxide of iron. 



Another porodite from Fatu Lnka, Timor, was described by the same author as a dirty 

 light- brown and brownish-green tufaceous rock with numerous serpentine and phrestine 

 (enstatite) fragnieuts. The rock effervesces feebly with acid. The serpentine shows 

 under the microscoj)e a network structure especially of the iron ore, while the interior 

 grains are greenish. A somewhat altered bronzite containing ore grains occurs. Tlie 

 cement is of a brownish shade, homogeneous and isotropic* 



Section V. — Pcridoiite. — lis Macroscopic Characters. 



The meteoric forms show in general a fine, more or less granular ground- 

 mass of some shade of gray — varying from a light gray or grayish-white to 

 a bluish or dark gray. Often they are porphyritic from enclosed chondri, 

 pyrrhotite, and metallic iron. Again they are apt to show brownish-yellow 

 spots of ferruginous staining, owing to the oxidation of the iron ores. The 

 grayish color appears to be mainly due to the finely divided state of the 

 component silicates, as well as to the natural color of the base and the en- 

 statite. The olivine is in too minute grains to show its characteristic 

 color, except in rare cases. The chondri frequently appear as gray, brown, 

 bluish, and white grains in the groundmass, giving the appearance of a 

 fragmental structure to the rock. 



The completely or coarsely crystalline forms, like those from Estherville 

 and Chassigny, present a gray to pale yellow crystalline mass closely 

 resembling that of the least altered terrestrial peridotites if not identical 

 with it. 



The iron ores occur as irregular masses, sometimes of a semi-sponge-like 

 structure, and in the form of metallic iron, pyrrhotite, chromite, and 

 magnetite. 



While the silicates are not usually sufficiently distinct to be determined 

 macroscopically, yet they sometimes are, and olivine in such cases shows in 

 pale green or yellowish grains, having a conchoidal fracture and the 

 same general characters this mineral has when it is of terrestrial origin. 



* Jaarb. Mijuw. N. 0. I., 1882, pp. 216-222. 



