THE METEOEIC PERIDOTITES. — LHERZOLITE. 95 



granular to compact groundmass, containing nickel-iron, pyrrliotite, spherules, olivine, 

 white crystal grains, and chromite. He states that the nickel-iron occurs in three differ- 

 ent forms : in large grains, in lamina;, aud iu ramifying, pronged grains sprinkled through 

 the groundmass. The surrounding groundmass is sometimes stauied, through the altera- 

 tion of the iron, to a brown color. 



The pyrrliotite occurs in small in-egular grains and granules of a tombac-brown color, 

 which, through a shght alteration, change to a dark steel-gray. 



The chromite is in very small black non-magnetic grains, aud only iu minute 

 amounts.* 



The specuuen purchased from Ward and Howell for the Whitney Collectiou has an 

 ash-gray color and shows a chondritic structure. It contains pyrrliotite and iron. 



Section : composed of a light-gray chondritic mass, containing grains of iron and 

 pyrrliotite. The groundmass is composed of olivine, enstatite, and some diallage. The 

 chondri are formed, m part, of grains and crystals of olivine and of enstatite, cemented 

 by a gray, iibrous base. Like those examined by the writer iu other meteorites he regards 

 these as the product of an arrested crystallization in a rapidly cooling mass — the 

 sohdificatiou taking place before crystallization was complete. Part of the enstatite 

 chondri do not show the usual eccentric structure, but a parallel, or sometimes a very 

 irregular one. 



The arrangement of the pyrrhotite and iron about some of the chondri reminds one 

 of the similar arrangement of the rejected or " pushed out " material about the feldspars 

 in some andesites. 



The iron is in part outside of, and in part entirely surrounded by, the pyrrhotite. 



Figure 1, Plate III., shows a large chondrus at the base of the figure, composed of 

 enstatitic, aggregately polarizing, fibrous material. The form shows the rounded indenta- 

 tions seen by Tschermak in the Tieschitz meteorite, and at its upper portion blends with 

 the groundmass, although distinct from it elsewhere. Under the microscope its boun- 

 daries appear to be those of a crystallizing mass and not those of a foreign inclusion in 

 the groundmass. At the left of this chondrus is another radiating fibrous one, com- 

 posed of enstatite ribs cemented by connective tissue of gray Ijase, holding metallic iron 

 grains. The remaining portions of the figure are composed of mLxed chondri and the 

 constituents of the rock. 



Figure 2, Plate III., shows the structure of a chondrus composed of olivine, enstatite, 

 iron, base, etc., with its blending at the bottom of the figure into the groundmass. 



Figure 3, Plate III., shows the relations of a mass of pyrrhotite (troilite) to an 

 inclosed mass of metallic hon, and the whole suiTounded by the chondritic groundmass. 



JVeio Concord, Gnernse// Co., Ohio. 



A crystalline granular rock containing pyrrhotite and iron, and showing yellowish- 

 brown spots of staining arcund the latter. 



Section : a light-gray crystalline mass of olivine, pyroxene and enstatite, and con- 

 taming u'on and pyrrhotite. The groundmass is stained a yellowish-brown in many 

 places. 



* See further tlie original paper of vom Rath. AbhaiulUingeu aus dem Gcbietc dcr Nat u rwissenschaftcii, 

 Mathematik, uiid Mediciii als Gratiilalioiisschrift dor uioderrhciiiisclieii Gcsellschaft fiir Xatiir-uiid Heilkuiidc 

 zur feier des fiiufzigjalirigen Jubilanms der kbiiighch rheiuisclien Friedrich-Wilhclms-Uuivcrsitiit. Buuu. 

 Am 3 August, 1S68, pp. 135-161, with plate. 



