A geode is a secondary geological structure characterized by a hollow, spherical or sub-spherical cavity within a rock lined with crystals or chalcedony layers. Collectors prize them for their surprise interior contents, which often include sparkling quartz or amethyst points. They are most commonly found in sedimentary strata like limestone or within certain volcanic gas bubbles.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

sedimentarycommon

Geode

Hardness: 7
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this geode?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch geode with a known reference. Geode sits at Mohs 7 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Geode leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Geode typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, gray, brown, blue, purple.
5
Look at form & habit
Typical habit: nodular.

Often confused with

Geode vs. its common look-alikes — and how to tell them apart in the field.

sedimentary

Concretion

Mohs 3-7

How to tell apart: Luster reads vitreous on Geode and dull on Concretion.

Compare →

Often found alongside geode

Minerals reported to co-occur with geode. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: SiO₂
Mohs hardness: 7
Density: 2.6-2.7 g/cm³
Colors: White Gray Brown Blue Purple
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal habit: Nodular
Cleavage: None
Rarity: Common
Uses: Collector, Decorative, Lapidary
Host rock: Limestone or Volcanic Rock
Typical price: $5-200 depending on size and interior crystal quality

Where rockhounds find geode

114 mapped spots

Classic worldwide localities

Keokuk, Iowa, USA
Durango, Mexico
Morocco
Brazil
Kentucky, USA

U.S. states with geode

Each link opens a state-specific list of mapped rockhounding spots that produce geode.

Field-hunting tip

Look in limestone or volcanic rock country — that is the host setting where geode typically forms. If you start seeing quartz, calcite, celestine in float, you are in the right ground. Field specimens usually show a nodular habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Iowa, Kentucky, Illinois — start trip planning there.

Browse 114 U.S. spots for geode →

Common questions

How do you identify geode?+

Mohs hardness is 7. It typically shows a vitreous luster. The streak is white. Common colors include white, gray, brown, blue.

Where is geode found?+

Notable localities include Keokuk, Iowa, USA; Durango, Mexico; Morocco; Brazil; Kentucky, USA.

Can I find geode in the United States?+

RockHoundR maps 114 geode rockhounding spots across 12 U.S. states — the top states are Iowa, Kentucky, Illinois.

How much is geode worth?+

Typical asking prices fall in the range of $5-200 depending on size and interior crystal quality. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like geode?+

Geode is most often confused with Concretion. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with geode?+

Geode commonly co-occurs with Quartz, Calcite, Celestine, Dolomite, Goethite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does geode form in?+

Geode typically forms in limestone or volcanic rock. Working float back to the host body is the standard way to chase a fresh occurrence.

What is geode used for?+

Geode is used in collector, decorative, lapidary.

Find geode on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.