Underclay

• (n.) A stratum of clay lying beneath a coal bed, often containing the roots of coal plants, especially the Stigmaria.
Found on http://thinkexist.com/dictionary/meaning/underclay/

Underclay

Underclay is a stratum of clay lying beneath a coal bed, often containing the roots of coal plants, especially the Stigmaria.
Found on http://www.probertencyclopaedia.com/browse/HU.HTM
No exact match found