You can't know what magic is inside these rough, dusty rocks until you reveal its secrets!
Geodes form in inside empty pockets of other rocks. In volcanic rock, geodes form inside lava bubbles. In sedimentary rocks, they may form in the space left by a burrow, tree root and such. Minerals dissolved in ground water are deposited in the empty space over thousands of years. Shiny crystal formations are often amethyst, quartz and calcite.