THE TERRESTRIAL PEKIDOTITES. — PICRITE. 140 



and have the cleavage of hornblende, garnet, olivine altered to serpentine in part, biotite 

 strongly dichroic and containing little opaque needles, diallage, and iron ore.* 



A siniihir serpentine was described by Datlie from Crossen, near Mittweida, in 

 Saxony ; but it appears to be a somewhat more altered rock {I. c, p. 245j. 



Variety. — Picrite. 



Austyia. 



Picrite, according to Tschermak, when in a fresli or little changed state, has a dark 

 green color, and varies from a finely crystalline to a plainly crystalline character. 



That from Sohle has a blackish groundmass containing a large number of olivine 

 crystals. Microscopically the groundmass holds granular feldspar, grains of magnetite, 

 scales of black mica, and little hornblende crystals. 



The Freiberg and CHlmhelherg picrite shows a dark groundmass holding olivine 

 crystals traversed by numerous fissures filled by a serpentinous mineral; also blackish- 

 green grains of diallage. The groundmass is similar to that of the Stihle picrite: gi-anu- 

 lar feldspar, biotite scales, magnetite grains, and a few hornblende crystals, with here and 

 there thin strings of serj)entine. 



The picrite from Schonau has a blackish-green groundm^ass holding olivine and dark- 

 green mica. The mica forms aggregations of scales. Much serpentine also occurs in the 

 rock. The groundmass consists of a granular feldspathic mass, grains and octahedrons 

 of magnetite, blackish-green augite crystals, rarely some needles of apatite, also calcite 

 grains, and some serpentine. 



An altered picrite from Solde is a dark greenish-gray rock flecked with pistacite 

 green spots. It contains altered diallage and olivine crystals, hornblende prisms, dark- 

 green mica plates, magnetite grains, and silicates like gymnite and palagouite. 



Another altered picrite from Bystryc, has a clear gray very fine-grained groundmass, 

 holding inclusions of bluish-gray to apple-green and blackish-green colors. Pseudo- 

 morphs after diallage and olivine occur, while the rock further contains magnetite and 

 fine fissures filled with calcite. 



The above picrites are stated to be eruptive in the Cretaceous. 



Steierdorfy Banat. 



A blackish rock resembling basalt, and containing porphyritically enclosed olivine and 

 quartz. It is somewhat porous, and holds calcite amygdules. The section shows that 

 the principal minerals are olivine, augite, and hornblende. Calcite occurs as an alteration- 

 product, and quartz as an inclusion, while an isotropic base was seen. The olivine is in 

 large, well-defined crystals, and in smaller rounded forms. It is for the most part fresh, 

 but it shows here and there along its edges and the borders of its fissures an alteration to 

 a dark brown radiated fibrous aggregate. The olivine contains inclusions of glass, augite, 

 hornblende, and picotite. The latter is in large brown isotropic sharply defined octahe- 

 drons. The augite is of a light-reddish color, and the crystals are fresh with a ft'eble 

 pleochroism. It contains inclusions of glass and picotite. The hornblende is of a dark 

 brown color, with strong pleochroism, and contains glass particles. Tlie hornblende is 



* Ncues Jain-. Miii., 1S76, pp. 244, 245. 



