248 



Figure 1. — Distribution of the most favorable areas for some potential mineral re- 

 sources off the Atlantic coast of the United States. The dashed line denotes the 

 position of the edge of the continental shelf, about 80 m deep in the south and about 

 140 m in the north. The area indicated for manganese nodules corresponds to the 

 surface of the Blake Plateau. 



PHOSPHORITE 



Phosphorite nodules occur in many surface samples from beyond the edge 

 of the continental shelf. They appear to be most abundant between depths 

 of about 200 and 500 m on the East Florida Escarpment, a 1° slope that 

 leads downward from the continental shelf to the Blake Plateau (fig. 1). They 

 are present but probably less abundant on the top few hundred meters of 

 the continental slope between the Blake Plateau and the vicinity of New 

 York City, and they are still less common on the continental slope east of 

 New York City. The nodules are brown dense masses as large as 8 cm in 

 diameter, and they have the X-ray and optical characteristics of apatite. 



