noun Download 🔗Share A variety of trap or basaltic rock, containing small cavities, occupied, wholly or in part, by nodules or geodes of different minerals, especially agates, quartz, calcite, and the zeolites. When the imbedded minerals are detached or removed by decomposition, it is porous, like lava. Examples : "The old volcanic flow, now visible as a weathered cliff face, was identified as amygdaloids due to the numerous cavities filled with sparkly quartz crystals. " geology mineral material Chat with AIVocabulary GamePractice Reading