blue mud

noun Geology, Oceanography.
  1. a deep-sea sediment of fine silt and clay that derives its bluish color from organic material and iron sulfide.

Origin of blue mud

An Americanism dating back to 1830–40
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for blue mud

Historical Examples of blue mud