Agate's geodes form when gas bubbles are trapped in solidifying lava. Agate is the most common variety of chalcedony which is a form of quartz.
These are then coloured and polished to give a beautiful and unique appearence, no two geodes are alike.
PLEASE NOTE: Due to the nature of this item, appearence and shape WILL differ to what is pictured. All sizes and weights given are approximate. No returns will be accepted based on the items appearence and colour