FIgurE 1.—Nodules on the conveyor belt after discharge from nodule/water 
separator during trial mining operations in the Atlantic Ocean in 1970. 
Courtesy : Deepsea Ventures, Inc. 
Surrace TEXTURE 
Ferromanganese nodules exhibit several types of surface texture: 
smooth with black lustrous patches, sandpaper-like or gritty, “goose 
bumps” or numerous small welts, and knobby. Generally two textures 
such as smooth and gritty are found on the same nodule. Many nodules 
have old fractures partly healed with additional manganese material 
and clay. 
STRUCTURE 
Variations in structure of the nodules are common; however, most 
appear to be layered in the form of concentric rings around a small 
nucleus. Each layer represents a compositional or mineralogical unit 
ranging in thickness from rings visible with the naked eye down to 
microscopic structures. The original surface of the layers was honey- 
combed, but the pores were subsequently filled with clay and the 
materials reorganized as the nodule grew by adding new layers. Some 
nodules or portions of nodules are nearly non-crystalline and, con- 
1 Raab, W. Physical and chemical features of Pacific deep sea manganese nodules and 
their implications to the genesis of nodules. In Ferromanganese deposits on the ocean floor, 
Horn, D. R., ed., IDOE National Science Foundation, Washington, D.C., 1972, p. 31—49. 
