148 PERIDOTITE. 



grains, colorless pyroxene (diopside), colorless mica, and chromite. The 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 chlorospinel. f 



Lepce, Austria. 



A blackisli 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 with a black powder ; as well as a liglit reddish-colored diallage, which 

 is fibrous and shows a feeble dichroism between light red and light greeu.| 



Fonlanapass, Locrisy Greece. 



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

 holding porphyritic crystals of diallage. 



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

 colorless fresh grains, travei'sed by numerous irregular fissures ; serpentine in tliin plates 

 along these fissures ; diallage, very fresh, and traversed by cleavage planes, l)ut sometimes 

 this mineral is clianged 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 Hyraettus, in Attica. 

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

 are much altered (bastite). 



In the section tlie rock sliows the ordinary network of serpentine, to which the 

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



Mohsdorf, Saxon?/. 



This rock, Dathe states, contains as its most pi'ominent mineral diallage. Sometimes 

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

 wliich 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. Porcn. Forh., 1877, iii. 250; Neues Jahr. Min., 18S0, ii. 197. 

 t Zeit. Deut. geol. GeselL, 1870, xxviii. 623-G25. 

 % C. V. Joliii, Jahr. Geol. Reiclis., 1880, xxx. 447. 

 § Min. Mittli., 1878 (1), i. 475-477. 

 II Neues Jahr. Min., 187G, pp. 233. 



