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, 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.
