Light brown, ferrugenous, crumbly concretionary bodies ranging in size from 5 to more than 70 mm., with an overall mean size of about 10-15 mm. These bodies have not been positively identified but are apparently of volcanic origin.
Cite the IMLGS database as: Curators of Marine and Lacustrine Geological Samples Consortium. The Index to Marine and Lacustrine Geological Samples (IMLGS). National Geophysical Data Center, NOAA. doi:10.7289/V5H41PB8 [date of access].