Ohh! Geodes! Those beautiful rocks filled with colorful, shiny crystals on the inside that look like a miniature sparkly cave. Did you know that many of the crystals of the jewels you own probably were formed inside one of these wonderful rocks? Well, now you know!

Geodes look like a regular rock on the outside, but inside they have a cavity. This is where the crystals will form, and it usually occurs in igneous rocks that are created by cooling lava or magma. When the rock is cooling down, it leaves a space inside kind of like a bubble. They can also be formed in sedimentary rocks such as limestone or sandstone.

Since these rocks are porous, many minerals slowly get inside and form layers in the empty space. Then, thousands of years later crystals are formed and fill the cavity, and in the case of larger crystals it can take up to a million years for them to grow!

What crystals are “born” inside a geode?

The crystals inside geodes can come in assorted colors, depending on the agate layer and the type of crystal. Most of these rocks are brown or white and if you ever see a very bright one, it was probably artificially dyed.

Quartz is a common crystal that is formed inside a geode. It is mostly white or transparent, but you can find it in purple (Amethysts); pink (Rose Quartz); Yellow (Citrine); brown (Smoky Quartz); green (Prasiolite); blue (Blue Quartz); and many more combinations!

Did you know that Cat’s Eye is a Quartz? Well, it is a Quartz with tiny Rutile inclusions which means it was also formed inside a geode. Its chatoyancy (the effect that makes the illusion of the cat eye) comes from fibrous inclusions or cavities within the stone.

Agate also develops inside a geode. Its color will depend on the distribution of several minerals within the stone and it usually appears in the form of concentric bands. For example, a red agate will have been created from iron oxides and cobalt, and a blue color will come from titanium.

Chalcedony is also a Quartz crystal, but it is too small to be seen with the naked eye. They cover the interior wall of geodes with a variety of colors. They can be white, gray, blue, yellow or orange.

Sedimentary rocks can create Silica crystals, and geodes found in central Spain usually contain Hematite which is a rock made of iron oxide used for magnetic jewelry. In the Midwest part of the United States you can find geodes with Dolomite, Calcite and Fool’s Gold.

From raw crystal to beautiful jewel

Jewelry-making is a complete profession that requires technique and creativity. You can make jewelry from several types of materials, but you can also use crystals from a geode.

The process of making jewelry with crystals starts with rock processing. Some geodes can be polished and left for display in, for instance, a museum or a store window, but they can also be broken apart to separate the crystal clusters and work in detail with the smaller pieces.

Once the crystals you want to use have been separated they can be grinded and polished. They can also be turned into different shapes to create any jewelry you want! For example, if you want to create a lapis lazuli anklet, you will need to make round shapes, and this would be the result:

Geodes create crystals small enough to fit in your hand, so the process to convert them into beautiful jewelry is not hard to handle. Still, there are exceptions! There is a cave in Mexico called Naica that has crystals that have grown up to 36 feet long! Can you imagine making a pendant out of those rocks?