ON OOLITES AND SPHERULITES 601 
black amorphous form of iron disulphide was described by Doss, 
who called it Melnikowite.’ It is found in the form of small lenses 
and occasional thin incrustations of Pelecypod shells in gray clays 
of Miocene age and especially in solid layers of a pyritic sandstone. 
These consist of a mixture of pyrite and of this amorphous iron 
ENON 
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Fic. 2.—Sketch showing the free ends of the siderite crystals extending into 
odlitic grains. From the same slide as the preceding figure. The large, nearly perfect 
crystal at the contact in the lower right-hand quadrant measures 0.08 mm. in length. 
Notre.—Owing to the extreme softness of the silicate, A. C. McFarlan, one of my students, who 
prepared this and numerous other slides for me, was unable to avoid scratches on the odlitic grains. I 
am also under obligations to P. Scherrer for valuable assistance in the making of microphotographs. 
disulphide and contain abundant sand grains which, however, are 
everywhere seen to be suspended in the groundmass of disulphide. 
This must, obviously, have been in the state of an amorphous 
1B. Doss, “‘Ueber die Natur und Zusammensetzung des in miocaenen Tonen des 
Gouv. Samara auftretenden Schwefeleisens,” VN. Jahrb. fiir Min., etc., Beil. Bd., 
XXXII (t912), 662-713. 
