Wondering if a crystal is real? Learn the differences between natural, synthetic, treated, and imitation crystals, plus practical clues that can help you recognize dyes, treatments, common fakes, and other warning signs before you buy.

From the outside, a geode often looks like an ordinary rock. Crack it open, however, and you may discover a glittering crystal-lined chamber that has been forming for millions of years. But why are geodes hollow in the first place? Learn how these fascinating formations develop, why crystals grow inside them, and what determines whether they remain hollow or become completely mineral-filled.