The Parklands

Wednesday Wonders – I wonder how geodes form.

At The Parklands, every day brings new opportunities to explore, but my favorite day is Wednesday! Each week, families meet at the PNC Achievement Center in Beckley Creek Park to discover and learn about a new science wonder. This week’s topic was, “I wonder how geodes form?”

First of all, what is a geode?

Geodes are round rocks with a hollow cavity filled with crystals. In order to see the beautiful crystals you must break open the rock! Geodes can range from the size of a golf ball to the size of a basketball.


So are all round rocks geodes?

No, but there is an easy test to figure out if what you’re holding is a geode.

  1. Shake the rock. Do you hear anything bouncing around inside? If so, you have found a geode with loose crystals!
  2. What if I don’t hear anything while shaking the rock? You might still have a geode, but the crystals aren’t loose. Instead ask yourself, “Does the weight of the rock match the size of the rock?” Geodes are never as heavy as you would expect because of their hollow cavity.

In class, we examined examples of geodes; looking at the crystal structure, size and color, we discovered that all geodes look different.

Why is this?  It all has to do with how and where they formed.

Formation of a geode requires the following:

  1. Sedimentary or Igneous rock
  2. Air, mud or trees
  3. Water and sediment
  4. Hollow cavity
  5. Time

How do all of these factors work together to create a geode? It’s simple!

Air bubbles in igneous rocks, animal burrows in mud or old tree roots create hollow cavities. The outer edges of the hollow cavity begin to harden into a spherical shape. Water, usually groundwater, flows through and around the geode. As water flows it picks up sediment, which is deposited into the cavity. After a couple thousand years, this mix of minerals and sediment creates a variety of crystal colors and sizes.  

Once the class had time to learn about these magical rocks, we strapped on our safety goggles and hammered away at some unopened geodes. Opening a geode is easy! All you need is a hammer. If you want a more even break on your geode, I’d recommend a rock saw or using a chisel with your hammer.

Check out more photos!

Geodes can be found all over the world! Floyds Fork is well known for its fossils, but not geodes; however, there are places throughout Kentucky and Indiana where you can search for geodes! Check out the Kentucky Geological Survey website for more information on geodes and a few suggestions on where you might be able to find them in the Commonwealth. 

Wednesday Wonders are interactive programs designed to spark the curiosity of young children. Each week, Parklands Interpretive Rangers explore a new science wonder with a story & related science experiment. 

This program is best suited for early learners (families with children under the age of 7). Each week these events are FREE to Members (but please RSVP below) and $5 for non-members (children and adults). Join us for these fun, early-childhood learning events!

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This is a great perk for Parklands Members with young kids! 

 Story by Olivia Kaiser, Interpretive Ranger

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