590 



AV. A. TARE OOLITES IN SHALE AND THEIR ORIGIN 



oolites are rarely larger tlian .26 millimeter and range from .1 to .13 

 millimeter. Those of the larger size comprise about 17 per cent of the 

 slide and the smaller ones probably twice this amount. 



Tlie larger oolites are concentrically banded (plate 21, figures 1 and 3), 

 and this feature is occasionally seen in the smaller ones. There is no 



Figure 2.-~Dist,iljuiion of the Oolites in red Phase of the Shale 

 Slightly enlarged 



variation iji their color, as the rings are due to the variations in the dia- 

 phaneity of the material. The interior is more opaque than the outer 

 zone, due, in part, to included clay. When several rings occur they are 

 always in the outer portion of the oolite (plate 21, figures 2 and 3). The 

 outer edge is not smooth, but irregular. Measurements of the central 



