Agate vs. Geode: What Is the Difference?

Agates and geodes, no matter how you look at them, are beautiful crystals.  Whether you’re purchasing them for decorative or metaphysical properties, you may be curious as to what the differences are between the two.   While both agates and geodes are considered to be mineral specimens and  hot ticket item amongst collectors, there are differences between the two.

In today’s guide, let’s explore the key differences between an agate and a geode.

What is the difference between an agate and a geode?

Formation

First, let’s talk about how agates and geodes are formed.

Agate is a type of microcrystalline quartz that comes in a variety of colors, such as black, purple, red, and green, to name a few.  It virtually comes in almost every color imaginable.  When an agate forms, it’s inside of a rock cavity, such as volcanic rock or a gas bubble, which is a result of silica precipitation that comes from mineral-rich water.  As water seeps into the rock cavities, the solution that’s rich with dissolved silica, as well as any other minerals, will slowly evaporate.  As this solution seeps out, the deposit will begin to layer, forming the agate layers.  It is the other minerals within that gives the agate its color and unique patterns.  This process is extremely slow, taking millions of years to form the agates you see today.

The key here is that agates are a form of chalcedony, usually with a banded pattern and inclusion of various minerals.

Geodes, on the other hand, will be more of an oval rock that’s hollow on the inside, lined with crystals.  Collectors refer to a potato shape.  These crystals will form as the groundwater seeps into that hollow cavity and leaves behind any dissolved minerals, which are then able to precipitate out of the water.  As this is done so, crystals will form on the wall within the cavity.  Geodes are found on a variety of rocks, including agate crystals; however, you can find them mostly with basalts and limestones.  A majority of the geodes you find will be filled with either quartz or calcite, usually with other minerals growing on the interior.

When you hear the term “geode,” it’s more of a description rather than a type of stone.  The thing to know about geodes is that they are hollow inside with crystals growing within, whereas agates will be solid.

Collecting

If collecting agates or geodes in the wild, some differences will exist.

For example, agates are commonly found on nodules, which means you will find round-like humps inside of a host rock.  The hump is embedded within the rock and will need to be split open to reveal the banding inside.  Oftentimes, you may find agate in larger veins or even in the seams of rock layers.

Geodes, similar to that of an agate, will be found in hollower rocks, and these will also need to be split open to reveal any crystals inside.  Geodes can be small or large, ranging from the size of a small coin to as large as a massive cathedral which can be six+ feet tall.  If you do find a geode on a quartz formation, you can often see forms of silica on the exterior banding.  This is a form of agate, only that it’s a very slim layer, mostly.

If hunting for geodes or agates, you can always tell the differences when exploring the stones around them.  Agates will almost always be heavier than the matrix stone they are held in since it’s commonly found in limestone or other soft rock.  Geodes, though, are much lighter than the stones surrounding them, which makes them easier to find.  Geodes often look like a round, potato-like shape, so they are easier to spot most of the time.

Value

Geodes are considered to be more valuable and rarer than that of an agate because of the crystals you can find within.  Commonly, agates are found throughout the world, which makes their value not as great as you think.  However, geodes are often restricted to certain areas, which makes them harder to find.  While they aren’t extremely rare, it’s just not as common as an agate.  Because of this, the value can be much more than that of a simple agate stone.  Geodes can be as little as a few dollars, whereas much larger, rarer specimens, can yield thousands.  The prices for both greatly depend on the crystal growth, size, clarity, cut, treatment, quality as well as weight.

Size

Quite possibly the biggest difference is the size.  Geodes will form macro crystals when forming, which means you can see them with your eye and no microscope is needed. Agates, as noted, is cryptocrystalline, which means there’s no visible ordered structure and you will need to use a microscope to see its crystalline form.  Agates will almost always form in irregular nodules whereas geodes will not.  As mentioned in the collecting section, agates will almost always be located on a much heavier matrix, whereas geodes are much lighter in weight.

Metaphysically

If you’re into metaphysical properties, there are some slight differences to know about.

Agates are said to be more of a grounding stone that helps bring stability to your life.  These crystals are said to help balance your emotions and energies.  Agates are also said to help improve your concentration as well as make wise decisions.

Geodes, since they have crystals inside, are said to amplify your energy and healing.  They are said to be known for their “stronger powers” and are believed to help you see the whole perspective in life, giving you a different view on things.

Are agates and geodes the same thing?

No, but it can be seen as such.

As mentioned, if the geode is a quartz and it’s blended with chalcedony, it can form bands on the exterior, which can be referred to as agate.  In this case, it’s still referred to as a geode but it will have agate mixed in.  In this case, it will be referred to as an agate geode.

Unlike a geode, which forms along the walls, agate will occupy this void space.  In this scenario, a geode can crystalize within an agate, per se.