Agate, agate geode is a non-uniformly used term from geology and mineralogy,

Agate_Dad on TikTok

Double geode agate cut open! | Taylor’s Rocksmithery

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The Factonaut on Instagram: "This geode is a natural rock cavity formed over millions of years. It begins as an empty space inside volcanic or sedimentary rocks, often created by gas pockets or decayed organic material. Mineral-rich water slowly enters the cavity and leaves crystal deposits on the inner walls. Over long periods, these crystals grow toward the center and create the crystal interior. The colors and patterns depend on the minerals present, such as quartz, amethyst, or calcite. Geod