Everything You’ve Ever Wanted To Know About Geodes
The idea of hidden treasure is hard to resist, but buried pirate loot doesn’t hold a candle to the riches of nature. Among the volcanic remnants of Brazil are nondescript rocks with a secret. Cracked open, they reveal a cavity lined with dazzling crystals. Whether you’re fascinated by science or just a lover of unique beauty, we’d like to share everything you’ve ever wanted to know about geodes.
What Is a Geode?
A geode is a hollow rock with a layer of inward-pointing crystals on the inside. They’re naturally occurring, created by forces like water, minerals, pressure, and changing temperatures. You might have seen geodes in textbooks, in gift shops, or even in museums. There’s no way to determine exactly what you’ll find inside a geode from its dull exterior, making it one of the true surprises of nature.
How Geodes Were Formed
The process began about 160 million years ago. As the Atlantic Ocean opened to split Africa and South America, the shifting tectonic plates triggered one of the world’s most significant volcanic events. Igneous rock flowed out of the rift, layering lava thousands of feet thick. It resulted in gas bubbles and lava tubes that hardened into cavities.
Then water entered the equation. Silica-rich water penetrated the cavities and ran through them, leaving behind the start of crystalline growth. The tiny crystals clung to the inner walls of the bubble. Thousands of years passed, then millions. Slowly, layers formed inside. First came agate, and then layers of quartz. Rock crystal grew larger with jagged points. Still buried deep inside the earth, radioactive minerals in the surround basalts began to decay. The geodes were irradiated, producing color centers in the quartz that transformed into colorful crystals like amethysts.
Where They’re Found
There are several places in the world where you can find geodes, although the quality of them can vary. Anywhere volcanic ash has helped form the landscape, you can find large deposits of limestone that are likely prime locations to hunt for geodes. Among the homes of geodes:
- Iowa. In fact, the state pays homage with Geode State Park, although you can’t remove any geodes from the premises.
- Ohio. A large tourist attraction called the Crystal Cave offers tours to educate visitors on geodes.
- Australia. The country also mines “thundereggs,” which are similar to geodes in that they have interesting interiors.
- Mexico. They produce “Las Choyas” geodes, or coconut geodes that are filled with chalcedony.
But the truly breathtaking geodes—the ones that you gawk at, and then take a selfie with—come from Brazil. In southeast Brazil, almost 400,000 square miles make up the Serra Geral Formation, a dramatic after-effect of those prehistoric flood basalts. That’s where the most significant geode deposit ever was discovered, located in the amethyst amygdule basalts of the Rio Grande do Sul region, which is abundantly rich with gems.
How Geodes Are Prepared
Geodes can be as small as baseballs or as large as 15 feet long. The challenge is in removing them intact from the surrounding rock. Every geode is one-of-a-kind, varying in size, color, shape, and crystal formation. Among the kinds of geodes you can buy are:
- Small, nearly round geodes.
- Slices of larger geodes.
- Twin cathedrals, or two sides of a large, vertically-shaped geode.
- Open two-sided cathedrals, which have a hole through the middle.
Depending on their intended use, geodes might be carefully sawn and polished to display their impressive crystal structure. A “cathedral” is usually weighted with a base, so it can be displayed upright. A polished slice of a geode could either be used as a piece of art on a stand, or used horizontally with protective glass on top as a masterpiece of a coffee table.
Many of the Brazilian geodes are also heated in kilns to intensify their natural colors. It’s not considered an “artificial” treatment because the heat is just mimicking a natural process. Geo-thermal heat did the same thing to the geodes before interruption; heat doesn’t change the molecular structure of the geode.
Creative Uses for Geodes
Many collectors think of geodes are ancient art—they are to be admired. You’ll see them on display in homes, at work as book ends, or on desktops as paperweights.
Some lucky kids receive geode kits as gifts or in school. They get to break open their own small geode with a hammer, and many go on to develop a passion for rock collecting. It’s a rewarding way to learn about what nature can do. Adults who love a good reveal enjoy the kits, too. If you want a more professional finish, you can open the geode more evenly with a rock saw.
So many people believe in the power of gems that, increasingly, geodes are placed in home to improve the energy of its surroundings.
- Amethyst Geodes. These gems are associated with love, protection, healing, and more. They are thought to relate to the Crown or Third Eye Chakra. Anyone looking to free themselves from addiction or unhealthy attachments might look for strength from an amethyst geode.
- Citrine Geodes. Some Brazilian geodes contain the amber crystals of citrine, a gemstone associated with passion, creativity, and optimism. Said to relate to the Solar Plexus Chakra, many believe that it can purify negative energy. If you’re seeking career or financial success, this could be the geode for you.
How To Choose Yours
The short answer? When you see a geode that stops you in your tracks—online or in person—that is the geode for you. Because it’s unique, it might not be available if you wait to purchase it. But if you’d like to take a more objective approach to buying a geode, you can take these qualities into consideration:
- Coloration. Deeper violets are considered more valuable in amethysts.
- Clarity. Just as with diamonds, clarity is a positive because of its ability to reflect and refract light.
- Points. You might have a preference for the shape and size of the crystal points.
After learning everything you’ve ever wanted to know about geodes, it’s time to get your own. At Brazil Gems, we select only the highest quality geodes for our inventory. See for yourself on our website, where we show our decorative geode hearts and functional geode tables; you can either start small or go big. Our citrine and amethyst cathedrals for sale represent the absolute best of Brazil—and Brazilian gems represent the best in the world.