Geode

['dʒiːəʊd]

(noun.) (mineralogy) a hollow rock or nodule with the cavity usually lined with crystals.

Checker: Patty--From WordNet

(n.) A nodule of stone, containing a cavity, lined with crystals or mineral matter.

(n.) The cavity in such a nodule.

Typist: Weldon

n. (min.) a rounded nodule of stone with a hollow interior.—adj. Geodif′erous bearing or producing geodes.

Checked by Hank