How are geodes formed?
Photo: oldbones
… and how do you open a geode without damaging the crystals inside?
You see geodes displayed in gift shops – sliced down the middle like a melon. They’re dull on the outside, but hollow and glittering with crystals on the inside.
Volcanic geodes are formed by cooling lava. Sedimentary geodes are formed underwater – possibly when sediments collect around the lifeless body of a sea animal. When the animal decays, it creates a cavity.
Both sedimentary and volcanic geodes need just the right combination of water, chemicals and pressure – to produce the crystals inside.
One way to open a geode – to reveal the crystals – is with a chisel and hammer. Score the geode completely around the outside where you want it to crack – usually in two equal halves. Keep going until it cracks and breaks apart. This will almost always work and won’t damage the crystals.
Trickier than opening a geode is recognizing one outdoors. Uncut, they look like your average rock. It helps to know where to look – a geodiferous outcrop of rocks. With practice, you can learn to identify a geode – they’re usually round or egg-shaped, and the weathered ones look like cauliflower on the outside.
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