geode

Noun
  1. (mineralogy) a hollow rock or nodule with the cavity usually lined with crystals (synset 109310723)
    referred to in: mineralogy - the branch of geology that studies minerals: their structure and properties and the ways of distinguishing them
    is a type of: nodule - (mineralogy) a small rounded lump of mineral substance (usually harder than the surrounding rock or sediment)

Other Searches