1 Answer

ge·ode
noun /?j??d/ 
geodes, plural

A small cavity in rock lined with crystals or other mineral matter

A rock containing such a cavity

Web definitions

(mineralogy) a hollow rock or nodule with the cavity usually lined with crystals
wordnetweb.princeton.edu/perl/webwn

Geodes (Greek γε?δης - j?-?ds, "earthlike") are geological rock formations which occur in sedimentary and certain volcanic rocks. Geodes are essentially rock cavities or vugs with internal crystal formations or concentric banding. ...
en.wikipedia.org/wiki/Geode

Geode is a series of x86-compatible system-on-a-chip microprocessors and I/O companions produced by AMD targeted at the embedded computing market.
en.wikipedia.org/wiki/Geode_(processor)

GEODE is a trade association that represents independent energy distribution and distribution-related companies, as well as other organisations in gas and electricity, privately or publicly owned, in Europe. ...
en.wikipedia.org/wiki/Geode_(trade_association)

A nodule of stone having a cavity lined with mineral or crystal matter on the inside wall
en.wiktionary.org/wiki/geode

A hollow rock cavity usually containing some form of one or more gemstones. Amethyst and Peridot are examples of gemstones found in geodes.
https://www.sanjuangems.com/learn-more/glossary/

a cavity, usually in a sedimentary rock, lined with crystals or other mineral matter; a rock containing such a cavity. [AHDOS]
https://www.memphisgeology.org/glossary_gh.htm

a round rock that has a hard "skin" on the outside and that usually is hollow on the inside, often lined or filled with mineral crystals, most common type is the quartz geodes
https://www.rocksforkids.com/RFK/glossary.htm

A sphere or oval shaped hollow or solid rock cavity containing crystallized minerals. Mineral crystals which may be found in Geodes are Quartz, Agate, Calcite, Peridot, Celestite, and many more.
https://www.rocksinmyheadtoo.com/Glossary.htm

Cavities in clay or other formations which have been incrusted with a wall of quartz or other mineral and which (later) separate as a hollow mass, the interior walls of which are usually studded with crystals.
www.krystallinegems.com/glossary.htm 

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