steinkern
noun
stein·kern
ˈs(h)tīnˌkern
plural -s
: a fossil consisting of a stony mass that entered a hollow natural object (such as a bivalve shell) in the form of mud or sediment, was consolidated, and remained as a cast after dissolution of the mold
Word History
Etymology
German, from stein stone + kern kernel, grain, from Old High German kerno; akin to Old High German korn grain