January 31

Geode Rocks: A Comprehensive Guide


Geodes are rocks that have crystals on the inside. They are usually round and can be found in sedimentary and volcanic rocks.

Minerals can form crystals by precipitation. It happens when fluids like groundwater or hot water come up from the ground and mix with minerals in the soil. The minerals then settle and form crystals around a hollow space. Geodes are rocks that have this kind of crystal inside them. They are often found near areas with volcanic activity because the hot water that helps create the crystals comes from underground volcanoes.

Many people collect geodes because they are pretty. People usually collect them when they are unopened because you can see the crystals inside when they are open. It takes a long time for these crystals to form- sometimes hundreds of years or even a million years! Let’s find out how they form.

Formation of a Geodes

Geodes are usually found in areas with a lot of mineral precipitation.

They are generally located in:

  • Stratified volcanic deposits of basalt and tuff, or
  • Stratified sedimentary carbonate deposits like limestones and dolomites.

Geodes form in particular environments where there are hollow bubbles inside the rocks. These bubbles can form when the air is inside explosive volcanic rocks or when animals and other biogenic activities burrow through the rocks.

The rainwater trickles through the hot bubbles, and the chemicals in the volcanic rocks mix with the water. It creates fluids that are rich in minerals. The fluid slowly builds tiny crystals or micro-crystalline bands inside the bubble.

The minerals found in water can fill up the inside of a geode over time. The water continuously moves over the rocks and leaves more minerals behind. The crystals inside can be different colors and often look like a candy center. Most geodes have an interior of either Calcite (CaCO3) or Quartz (SiO2).

Almost all geodes have quartz in them because quartz is the most common mineral on Earth. Geodes are more likely to form when there are a lot of quartz-containing rocks near each other.

Geodes are usually smaller if they form in Sedimentary rocks like limestones, Dolomites, and calcareous shale. It is because gas-filled voids in these rocks or shells and the burrowing activities of animals often leave a cavity for the chemical precipitation of minerals. These cavities get filled with quartz, opal, agate, or carbonate minerals.

The Secret Behind Their Vibrant Colors

Geodes come in colors like blue, pink, purple, and red. It happens because of the different minerals in the water. Suppose there are traces of elements like iron, sulfur, copper, or magnesium in the water. In that case, it will give the geode a different color.

What Does A Geode Worth?

These pieces of nature’s artwork are collectible and priced from $30 to $500. Geodes are sold at various auctions for art galleries, collectors, museums, and even at different high-end gift shops. The value of a geode is determined by its color saturation, tone, symmetry of its exterior shape, and size.

The crystals with deep tones and intense color saturation are expensive. The better the quality of amethyst, the less it costs. It is not as valuable if an amethyst crystal loses its color due to weathering and becomes dull or has reddish-purple hues. Amethyst can lose its purple color and become soft yellow or citrine when exposed to very high temperatures.


Brazil, Siberia, the USA, and Mexico are the most beautiful geodes. Geodes have unstable rocks inside of them that can easily break away. The rocks are usually calcite, tuff, or basalt. They can be collected when the host rock weathers away. Geodes that are mined from the ground can often be damaged.

Read more: How to Collect Crystals

Frequently Asked Questions About Geode Rocks

Is a Geode Rock Worth Anything?

Geodes can be worth anywhere from $5 to more than $1000, depending on their type and location. The price of a geode can vary depending on if the crystals inside it are exposed.

Where Are Geode Rocks Found?

There are geodes to be discovered in every region of the planet. Some of the best places to find them are desert areas, volcanic ash beds, and areas with limestone. Geodes can also be found in many different places in the U.S., including California, Utah, Arizona, Nevada, and Iowa.

Are Geode Rocks Rare?

Geodes are found worldwide, but some places have more than others. For example, you can find a lot of them in the desert. Geodes also sometimes form near volcanoes or in areas with many limestones. Check out western states such as California, Arizona, Utah, and Nevada if you’re searching for nice spots to hunt.

What Are Geodes Good for?

Geodes have many uses. People use them to communicate with divine beings, to help create better moods and energy, and to help with meditation and decision-making. It is because the different crystals inside geodes can affect people differently.

How Do You Tell if a Rock Is a Geode From the Outside?

Look for rocks that have a bumpy, unique texture on the exterior. Geodes are rarely perfectly smooth. They will usually have a cauliflower-like appearance on the surface. Check for any signs of minerals inside the geode.

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