On a visit to Tucson, relatives took me to a gem and mineral show where we saw a collection of geodes. Ordinary on the outside; beautiful on the inside. Will you please tell us how they are formed and ...

Geode is a type of sedimentary and volcanic rock that is hollow, vaguely circular rock, in which masses of mineral matter (which may include crystals) are sequestered. The term 'Geodes' was derived ...