geode

English Thesaurus

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

hypernym	:	nodule,
definition	:	(mineralogy) a small rounded lump of mineral substance (usually harder than the surrounding rock or sediment) (noun.object)

domain category	:	mineralogy,
definition	:	the branch of geology that studies minerals: their structure and properties and the ways of distinguishing them (noun.cognition)