An echinoid geode is a fossilized sea urchin that has had its internal cavity filled with secondary mineral crystals, typically quartz or calcite. Collectors look for well-defined external test (shell) features paired with a hollow interior lined with sparkling druzy crystals. They are most commonly recovered from limestone or marine sedimentary deposits where groundwater infiltration facilitated mineralization.
Is this echinoid geode?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch echinoid geode with a known reference. Echinoid Geode sits at Mohs 7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Echinoid Geode leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Echinoid Geode typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: gray, white, clear, brown, tan.
- 5Look at form & habitCrystal system: trigonal. Typical habit: druzy.
Often confused with
Echinoid Geode vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside echinoid geode
Minerals reported to co-occur with echinoid 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
- 2.65 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Druzy
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Decorative
- Host rock
- Sedimentary Limestone
- Typical price
- $20-200 depending on size and crystal quality
Where rockhounds find echinoid geode
1 mapped spotsClassic worldwide localities
- Florida
- Morocco
- Madagascar
- United Kingdom
Field-hunting tip
Look in sedimentary limestone country — that is the host setting where echinoid geode typically forms. If you start seeing quartz, calcite, chalcedony in float, you are in the right ground. Field specimens usually show a druzy habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Florida — start trip planning there.
Common questions
How do you identify echinoid geode?+
Where is echinoid geode found?+
Can I find echinoid geode in the United States?+
How much is echinoid geode worth?+
What rocks look like echinoid geode?+
What minerals are found with echinoid geode?+
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Find echinoid geode on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
