@bdattilo, @bmacfadden, @crobins, @john-christian, @rebecca-freeman,
I agree with Jack’s comment, there is no need to make it more complicated. Grabau’s definition is very good and I guess since he was half German he should have known the meaning of Steinkern also very well 😉
Btw: with this section: “… Occasionally the space between the two molds, i.e. that formerly occupied by the shell, may be filled by infiltrations, and a cast of the original shell may thus be produced.” he describes the “Ersatzschalenerhaltung” I explained earlier (ersatz shell).
cheers
Ronny