STRUCTURES COMMON TO CRYSTALLINE SPHERULITIC FORMS 401 



ular aggregate of the silicates, as in figure 4, plate 2, where the appear- 

 ance at once suggests a metamorphism of the glassy base in a porphyritic 

 chondrule. Nowhere do I find any true undifferentiated glass, and there 

 is but little maskelynite. The observations hold true of the stones {Ccl^) 

 of Djati, Pengelon, Kernouve, Long Island, and others of this group. 

 That these were derived from the tuffaceous forms would seem to be defi- 

 nitely settled by the facts stated, and particularly by the presence of the 

 slightly altered and often more or less fragmental chondrules, which are 

 so obviously foreign to their present position. 



Structures common to crystalline Forms 



The so-called crystalline chondrites consist of a firm, holocrystalline 

 ground in which are imbedded occasional chondroidal forms. The most 

 striking feature of the last mentioned is their lack of symmetry or per- 

 fection of outline, as compared with those in the tuffaceous varieties. 

 (See figure 5, plate 2, and figure 1, plate 3, from the crystalline chondrite 

 of Eenazzo, Italy, and Estacado, Texas.) Another feature which is also 

 found in the white, gray, and intermediate forms, yet to be noted, is the 

 rarity of glass in the chondrules themselves and the obliteration of their 

 apparent original outlines. In figure 2, plate 3, from the Ensisheim 

 stone, it will be noted that the porphyritic chondrule merges gradually 

 into the ground-mass, and that, further, the interstices of the phenocrysts 

 are occupied not by glass, but by fine granular matter — a condition to at 

 once suggest the crystallization of the glass base of a porphyritic chon- 

 drule during the general process of metamorphism which the stone as a 

 whole has undergone.^'' Maskelynite and merrillite are almost universal 

 characteristics of this group, as of the other altered forms described. 



Structures common to white, gray, and intermediate Forms 



Passing to consideration of the white, gray, and intermediate groups, 

 one finds the same strongly marked differences in internal structure with- 

 out change in mineral composition, though whether these differences are 

 due to metamorphism or original crystallization is not always easily ap- 

 parent. They show a gromid distinctly cataclastic for the most part — a 

 structure which is certainly in part due to crushing, as argued by Eenard. 



ic The views thus above expressed are apparently fully in accord with those of Wahl, 

 where he says : "Die Verfestigung und die Bntstehung der kristallinen Struckturen der 

 Chondrite Hifst slch auf eine Erhitzung (Thermometaraorphosel zuriickfiihi-en. durch 

 welche die INlineralsplitter und Chondreu, je nach der Intensitilt der Hitzewirkung, mehr 

 Oder weniger kriiftig aneinander geschweifst werden und die urspriinglich vorhandene 

 Tuffstruktur verwischt wird." 



