The Truth About Man-Made Geodes: How to Identify Them Like a Pro (2023)

All About Fake Geodes

One of the main concerns for any rock collector is coming across fakes. Learning how to spot them is one of the basics of the hobby, and it’s not as hard as you’d think. If you’re still learning, however, it always helps to have just a bit of guidance.

That’s what I’m here for. We’re going to dig into the world of fake geodes and answer some of your questions, beginning with are there fake geodes?

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Are There Fake Geodes?

The Truth About Man-Made Geodes: How to Identify Them Like a Pro (1)

Well, yes. But there’s fake everything out there, the question is whether or not it’s meant to fool collectors or just to be an interesting object in its own right.

In the world of rock collecting, few things are more frustrating than running across fakes. Trickery is rather common in the mineral collecting world, unfortunately, so learning how to source and identify fakes is one of the first things you should do.

There’s more than one sort of fake. They range from plastic piles of junk that kind of look like the real thing, all the way to entirely synthetic stones created through complicated chemical procedures.

Fake geodes, those that are entirely constructed, are a thing.

But they’re unlikely to be sold to you directly as a geode, they’re often made of resin and parts of larger sculptures. They can easily be identified: they’ll readily scratch with any kind of steel tool and feel wrong in the hand.

I’ve seen anecdotes of entirely synthetic geodes grown that can be identified by a lack of internal flaws, but this is unlikely. It’s most likely someone who misheard people talking about synthetic gemstones and transferred the property to geodes.

Geodes vs Vugs

Now, not everything sold as a geode is actually a geode. The ones labeled as a geode are often vugs found in basalt, with the outer edges trimmed down to create a vague geode shape. They’re not strictly a spherical or semi-spherical formation with a hardened outer layer, but instead a pocket of crystals filled inside of a hard rock.

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The difference is minor for a collector, but an important distinction for a geologist.

These are sometimes labeled as fake by those who are prone to jumping the gun. It’s easy to see why: they don’t have the typical outer geode layer and if you’re not familiar with the stone you’ll find cut-down basalt looks quite a bit like concrete.

The vast majority of amethyst “cathedrals” are in the same boat. They’re from the inside of a basalt flow and when the vug is found the miners cut around it and then trim down the exterior to reduce the weight for handling and shipping.

The Truth About Man-Made Geodes: How to Identify Them Like a Pro (2)

Like many stones, faking geodes really isn’t a profitable affair. They’re already cheap and many of them end up in countries like India where stone cutting is a big industry.

That said, there is one common type of “fake” geode we need to discuss.

Dyed Geodes

Quartz or calcite geodes can be dyed using the same process as that used to color agate slices. Strongly colored geodes are invariably dyed unless they happen to be amethyst.

These dyed geodes are cut and then soaked in the dye for weeks or months. The dye works its way through pores and cracks in the material in order to create the illusion of a strongly colored geode.

The Truth About Man-Made Geodes: How to Identify Them Like a Pro (3)

The vast majority of these are labeled as dyed. Remember what I said earlier about geodes being cheap? Those that end up dyed will experience a price increase for being dyed since they’re mostly decorative objects meant for casual fans of rocks.

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Dyed geodes can be identified the same way as any other dyed stone. The color showing up most strongly in cracks and crevices is a dead giveaway, but few geodes have strong color anyways. The strongest colors you’ll find are in high-grade amethyst from Brazil, there are no natural bright green or deep blue geodes.

Whether or not you want to display these is your own choice. I usually don’t place them with other mineral displays but I’ve had a few of them over the years.

How to Detect a Fake Geode

The Truth About Man-Made Geodes: How to Identify Them Like a Pro (4)

If you think you have something fake on your hands, it’s time to get a bit of testing done.

Visual Inspection

Visual inspection is the best spot to start. Dye, as mentioned above, is the most common “fake” that’s done to geodes. They’re sometimes sold at high prices to the unwary as some kind of rare oddity.

Check around the exterior edges of the hardened geode. Does it look like a bunch of little layers of compact, hard stone? This exterior chalcedony found in the majority of quartz geodes is hard enough to take it simply wouldn’t be worth the effort.

I’ve never seen anyone attempt a fake geode, even in an art piece, that wasn’t simple quartz or amethyst crystals. Take a look, they should be hexagonal in structure and often tightly packed together. Amethyst may have color zoning, but the color won’t gather in the cracks.

Hardness Testing

Hardness testing is your next best bet. Calcite will scratch with a knife, but it’s not faked very often. Scratching quartz with a knife is borderline impossible due to the hardness difference and it’s a good way to easily check.

Overall Feel

Like any other stone (barring amber), a geode should also feel a bit cool to the touch. If it feels warm or plastic then you don’t have a real geode in front of you.

On occasion, people will make a “geode” by sticking a bunch of crystal points in polymer clay, in which case the exterior will make the fake obvious but the crystals will still feel right.

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Altered vs Fake

Testing may need to be done on rare occasions, but the truth of the matter is that geodes are far more likely to be an altered stone rather than something truly fake.

However, dyed geodes do serve an important purpose even for those who only want natural stones. You can use their description to vet a seller, anyone who sells a dyed geode as natural is already up to some shady business and should be avoided.

So, there you have it. Fake geodes are rare and easily tested, while the majority of dyed specimens are labeled correctly.

Still, as a beginner in the hobby, it’s always important to keep asking questions and expanding your knowledge base. Learning about fake stones is definitely an important part of that.

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Jeremy Hall

(Video) All About Geodes and How They Are Formed

Jeremy is a professional writer, but his real passion lies with stones. With two decades of collecting behind him, as well as a decade of cutting, he loves to share his broad experience and knowledge about rockhounding. These days he can be found in his workshop, setting the stones he dreamed of as a child. You can find his knowledge here, and his handiwork at his Etsy shop.

The Truth About Man-Made Geodes: How to Identify Them Like a Pro (6)

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The Truth About Man-Made Geodes: How to Identify Them Like a Pro? ›

Jiggle your rock around close to your ear and listen for any movement inside. If you hear anything jostling around inside then you can be sure you've found a geode. That sound is a sure sign that there is empty space within the rock for material to move around in.

How do you identify a geode without breaking it? ›

Jiggle your rock around close to your ear and listen for any movement inside. If you hear anything jostling around inside then you can be sure you've found a geode. That sound is a sure sign that there is empty space within the rock for material to move around in.

How do you know if a geode is valuable? ›

A geode can be worth anywhere from $5 to more than $1000, depending on its type and location. The price will vary widely based on whether the rock has been cut open because geodes often contain crystals inside of them which make them more valuable when exposed correctly (e.g., cutting along an axis).

How do you tell if a rock has a geode inside? ›

If the rock feels lighter than that surrounding rocks, it may be a geode. Geodes have a hollow space inside, which is what allows the crystals to form. You can also shake the rock next to your ear to test whether it is hollow. You may hear small pieces of rock or crystal rattling around inside if it is hollow.

What is the rarest geode color? ›

The rarest and most valuable geodes contain amethyst crystals and black calcite. When are you looking to enroll?

How do you tell if a river rock is a geode? ›

Look for a rough and bumpy spherical rock

The first step in identifying a geode is examining its exterior. While geodes are typically rough and bumpy, they should also have a somewhat spherical shape. This is because the minerals and crystals inside have grown in a circular pattern around the air pocket.

How do you pick a good geode? ›

Look for geodes with thin outer walls and a small base. Geodes are sold by weight, so the more crystal, compared to the outer layer of sedimentary rock, the better. As mentioned above, the heavier the geode, the more expensive it will be. Additionally, the size of each crystal point will also determine value.

What to look for when finding a geode? ›

Look for rocks with a bumpy texture.

When you're searching, you want to look for lumpy rocks. Geodes have lots of bumps and texture to them, so steer clear of any rocks with a very smooth surface. Geodes tend to resemble cauliflower in texture.

Where are geodes most commonly found? ›

Geodes are found all over the world, though they are most concentrated in desert regions. Other places where geodes are common are volcanic ash beds and areas containing limestone. There are geode collecting sites all over the U.S. in California, Utah, Arizona, Nevada, and Iowa.

Can diamonds be found in geodes? ›

Bristol Diamonds are quartz crystals found in geodes and geological rock formations which occur in dolomitic conglomerate in the Avon Gorge in Bristol, England. Their origin lies in geological processes of the Triassic period, about 250 to 200 million years ago.

How many years does it take for a geode to form? ›

How long does it take for a geode to form? Over thousands of years, these layers of minerals build crystals that eventually fill the cavity. How long this takes depends on the size of the geode. The largest crystals can take a million years to grow!

What is the most common crystal in a geode? ›

Most geodes contain clear quartz crystals, while others have purple amethyst crystals. Still others can have agate, chalcedony, or jasper banding or crystals such as calcite, dolomite, celestite, etc.

What is the water inside a geode? ›

Enhydro agates are nodules, agates, or geodes with water trapped inside its cavity. Enhydros are closely related to fluid inclusions, but are composed of chalcedony. The formation of enhydros is still an ongoing process, with specimens dated back to the Eocene Epoch. They are commonly found in areas with volcanic rock.

What is found on the inside of a geode? ›

The hollow interior often is nearly filled with inward-projecting crystals, new layers growing on top of old. The crystals are of quartz, less often of calcite or dolomite, and sometimes of aragonite, ankerite, hematite, magnetite, pyrite, chalcopyrite, and sphalerite.

What is the ball inside geode? ›

A geode which is completely filled with small compact crystal formations such as agate, jasper or chalcedony is called a nodule.

What is the most amazing geode? ›

The Pulpi Geode In Spain

It is 26 feet long, 6 feet wide, 5.5 feet high and lined with massive selenite crystals up to 6 feet long. The selenite crystals are incredibly pure, so translucent that you can see your hand through them.

Is a rainbow geode real? ›

They are naturally formed quartz geodes bonded with metal vapours to make their beauty POP! It's hard to resist the allure of a rock that is rugged and weathered on the outside, yet so sparkly and colourful on the inside. A geode typically begins when a cavity forms in a rock.

What is a thunder egg rock? ›

Thunder eggs are spherical objects which form in some types of silica-rich volcanic rocks (e.g. rhyolites). As the volcanic lava cooled, trapped steam and other gases formed an expanding bubble.

How old is water inside a geode? ›

They published the findings in the journal Nature in May, showing that the water is between 1.5 and 2.6 billion years old – meaning it has been totally isolated for that long.

Should you wash geodes? ›

EASY METHOD: Simply wash the geodes in plain water with a bit of laundry detergent (or dish soap), then let them soak in a tub of water with 1/4 cup of ordinary household bleach for two days. This cleans most of the heavy grit off the geodes.

What is the largest geode ever found? ›

A researcher stands inside the Pulpí geode, the largest documented geode in the world, located at a depth of about 150 feet (50 meters) in a former silver mine in southeast Spain. Image via Hector Garrido. The Pulpí geode – discovered in 1999 – is often said to be the biggest geode in the world.

What rocks are best for geodes? ›

Geodes do not form in just any type of rock and are generally only found in a handful of rock types that may be prone to these small air pockets forming, such as basalts and limestones.

Do geodes form in any rock? ›

Geodes are more or less spherical or egg-shaped rocks containing a hollow cavity which is lined with crystals. They form in both igneous and sedimentary rocks.

What rocks carry diamonds? ›

Magmas That Carry Diamonds. Diamonds are known to be carried to the earth's surface in only three rare types of magmas: kimberlite, lamproite, and lamprophyre. Of the three types, kimberlites are by far the most important, with several hundred diamondiferous kimberlites known.

What rock is diamond found in? ›

Diamond is only formed at high pressures. It is found in kimberlite, an ultrabasic volcanic rock formed very deep in the Earth's crust. The extreme pressures needed to form diamonds are only reached at depths greater than 150km.

What do raw diamonds look like in rocks? ›

On the other hand, raw diamonds are uncut and unpolished. In other words, they have not been altered or tampered with after they were discovered. Raw diamonds look like transparent stones with yellowish or brownish tints. There are some that are colorless but these are rare.

What is an egg geode? ›

Eggshell Geode

This simply means that there are suspended particles of alum powder in it, and as the solution cools, these particles of alum begin falling to the bottom. As the alum particles settle on the bottom, they begin crystallizing.

Can you make your own geodes? ›

Place half an eggshell in a small bowl. Fill the small bowl with salt water solution. Let soak for 3-7 days. Observe the salt particles crystallize on the eggshells to create beautiful geodes!

What is the rock that looks like glass? ›

Obsidian doesn't look like your typical rock. In fact, it looks more like dark glass than a rock you'd pick up in your backyard. That's because obsidian is volcanic glass. It forms when volcanic lava cools so quickly, there's no time for crystals to grow.

What is the rarest crystal mineral? ›

Painite : Not just the rarest gemstone, but also the rarest mineral on earth, Painite holds the Guinness World Record for it. After its discovery in the year 1951, there existed only 2 specimens of Painite for the next many decades. By the year 2004, there were less than 2 dozens known gemstones.

What do people do with geodes? ›

Geodes can be used for a multitude of purposes, including assistance with decision-making, facilitating communication between people in the same healing fields or with divine beings, creating good moods and energies, help with meditation, stress relief, and more.

What is the white stuff in geodes? ›

Kaolinite occurs in solid geodes as compacted masses of snow- white, earthy powder, usually surrounded by coarsely crystalline calcite in the lower part of geode specimens.

How do you tell what color a geode will be? ›

Iron will give crystals a red or purple color, titanium will create blue, nickel or chromium leads to green, and manganese produces pink crystals. While geodes can be naturally colorful some are artificially dyed. These dyed stones often have a brighter, more intense color than what appears naturally.

What is the difference between an agate and a geode? ›

In a lot of ways, agates have inclusions, while geodes are inclusions in the host rock. It's an important distinction to make. But the biggest difference is the fact that geodes are a specific form of mineral, while agates are a specific type of mineral. Any comparison between them should take that into account.

Do all geodes float in water? ›

No, because if they form in the ocean, they have seawater inside. Not air. So their density cannot be lower than that of seawater, and they cannot float.

How can you tell if a geode has been dyed? ›

While geodes can be naturally colorful some are artificially dyed. These dyed stones often have a brighter, more intense color than what appears naturally. Why do people dye geodes? Colorful geodes tend to sell well and can be a cheap way to imitate rare stones.


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