94 PEEIDOTITE. 



pyroxene minerals. The specimens purchased for the "Whitney Collection from Ward 

 and Howell show an ash-gray groiuidmass, stained witli brownish spots of rust, and con- 

 taining grains of grayish-brown olivine. 



Section : a yellowish-brown and grayish groundmass containing iron. On one side a 

 black band forming the exterior (rind) of the meteorite is preserved. The groundmass 

 is composed of olivine grains with some enstatite. The yellowish-brown color is owing 

 to a ferruginous staining of the silicates, while the rind is composed of the same minerals 

 as the interior, but owing to the heat to which it has been exposed it has been burned 

 black. Clear grains of untouched sihcates (olivine and enstatite) are to be seen both m 

 the interior and in the crust. 



In one corner of the section a small amount of a fine ash-gray semi-base was 

 observed cementuig olivine grains. 



The mixed enstatite and augite with iron, and a ferruginous stained groundmass are 

 shown in figure 4, Plate III. 



Goalpara, India. 



The Goalpara meteorite, according to Tschermak, is a dark-gray granular rock, having 

 a porphyritic structure. In the deep-gray groundmass are inclosed clear colorless and 

 yellowish grains. 



On microscopic examination the meteorite was found to be composed of enstatite, 

 olivine, iron, and pyrrhotite. 



The enstatite shows well-marked cleavage-planes running in two directions, forming 

 an angle of 92° with each other. The olivine has no cleavage, and does not occur in 

 distinct crystals, but in minute grains united together. The groundmass in which the 

 olivine and enstatite are mclosed is very fine-grained. Microscopically it is seen to be 

 composed of minute transparent gi'ains, apparently olivine, and untransparent forms. 

 These last are of three different kinds : iron, pyrrhotite, and coal-like bodies. The iron 

 forms a sponge-like mass, with extremely thin cell-walls composed of cubic crystals. The 

 coal-like bodies are described as being in all their properties similar to soot (graphite?). 

 The groundmass is said to appear in branching, leaf-like, thread-like, and dot-like forms, 

 wmding between and around the grains forming the olivine clusters. 



The student is referred to Tschermak's paper for the complete description and figures 

 illustrating the microscopic structure.* 



Variety. — Lherzolite. 



PuUusJc, Poland. 



The Pultusk meteorite on the fresh fracture shows, according to Werther, as a light- 

 gray rock, part very fine-grained, and part of a somewhat coarser texture. This is 

 interspersed with numerous white and yellowish points, showing metallic lustre, also 

 brownish-yellow spots in the groundmass. He regards the rock as composed of nickel- 

 iron, olivme, enstatite (?), and chromite.f 



This meteorite was further described by Dr. G. vom Eath as composed of a fine 



* Sitz. Wien. Akad., 1S70, Ixii. (2), 8.55-S65. 

 t Scliriften, Kongsberg Gesell., 1S6S, ix. 35-40. 



