148 PERIDOTITE. 



grains, colorless pyroxene (diopside), colorless mica, and chromite. Tlie olivine is fresli, 

 and with the pyroxene is almost free from inclusions. The chromite is brownish on the 

 edges, and is often surrounded or accompanied by the mica* 



This rock is said to be associated with schists, and to be a concordant part of 

 them. 



Varallo, Sesia Valley. 



Prof. A. Stelzner described a fine-grained greenish-black rock from Varallo, in Sesia 

 Valley, as composed of olivine, hornblende, and bronzite in nearly equal amounts. Green 

 grains were observed which were isotropic and regarded as probably chlorospiuel. f 



Lepcc, Anstr 



•lU. 



A blackish fine-grained olivine mass with light greenisli-gray foliated diallage having 

 a metallic lustre. 



The section is composed of predominating somewhat serpentinized olivine, whose 

 fissures are filled witli a black powder ; as well as a liglit reddish-colored diallage, which 

 is fibrous and shows a feeble dichroism between light red and light gi-eeu.ij: 



FoiUanapass, Locris, Greece. 



According to Becke the rock from this locality is a light-colored fresh olivinfels, 

 holding porpliyritic cry.stals of diallage. 



In the thin section it is seen to contain the following minerals : olivine in irregular 

 colorless fresh grains, traversed by numerous irregular fissures ; serpentine in tliin plates 

 along these fissures ; diallage, very fresh, and traversed by cleavage planes, but sometimes 

 this mineral is changed to a rhombic fibrous alteration-product ; and picotite, in little 

 reddish-brown, translucent quadratic or hexagonal sections. 



A somewhat similar rock comes from Pyrgos, at the foot of Hymettus, in Altica. 

 This has a black and green spotted groundmass holding large crystals of enstatite which 

 are much altered (bastite). 



In the section tlie rock shows the ordinaiy network of serpentine, to which the 

 olivine has been entirely changed. Picotite and magnetite occur.§ 



Mohsdorf, Saxony. 



This rock, Dathe states, contains as its most prominent mineral diallage. Sometimes 

 along the fissures are alteration-products of calcic carbonate and iron. The olivine 

 which is held by the diallage is generally altered to serpentine, which is filled with a 

 powder of iron ore. Some garnet occurs. || 



Gillsberg, Saxony. 



According to Dathe, this is a dark green rock composed of dark brown to black 

 elongated crystals, which in the thin section are dichroic from light brown to dark brown, 



* Geol. Foreu. Forh., 1877, iii. 250; Neucs Jalir. Miu., 18S0, ii. 197. 

 \ Zeit. Deut. geol. Gescll., 1876, xxviii. 023-025. 

 % C. V. John, Jahr. Geol. Reiclis., ISSO, xxx. 4i7. 

 § Mill. Mitth., 1878 (1), i. 475-477. 

 II Neues Jahr. Min., 1870, pp. 233. 



