Echinoids are the fossilized remains of sea urchins, often found as spherical or heart-shaped mineralized tests in marine sedimentary deposits. Collectors look for well-preserved ambulacral pores and distinct five-fold symmetry patterns on the surface of the shell. They are frequently discovered in chalk beds or limestone layers that were once ancient sea floors.

Hardness

3-4

Mohs

Luster

Dull

Streak

White

Transparency

Opaque

fossilcommon

Echinoid

Also: sea urchin fossil

Hardness: 3-4
Luster: Dull
Streak: White
Transparency: Opaque

Is this echinoid?

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 echinoid with a known reference. Echinoid sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Echinoid leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Echinoid typically shows a dull luster.
4
Match the color range
Compare against the expected color range: white, gray, tan, brown, black.
5
Look at form & habit
Typical habit: test (the hard shell or skeleton of the echinoid).

Often found alongside echinoid

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

All properties

Chemical formula: CaCO₃
Mohs hardness: 3-4
Density: 2.6-2.9 g/cm³
Colors: White Gray Tan Brown Black
Streak: White
Luster: Dull
Transparency: Opaque
Crystal habit: Test (the Hard Shell or Skeleton of The Echinoid)
Cleavage: None
Rarity: Common
Uses: Collector, Decorative, Educational
Host rock: Sedimentary Rocks Like Limestone and Chalk
Typical price: $5-50 for common specimens, $100+ for large or rare articulated fossils

Where rockhounds find echinoid

Classic worldwide localities

England
France
Morocco
USA
Germany

Field-hunting tip

Look in sedimentary rocks like limestone and chalk country — that is the host setting where echinoid typically forms. If you start seeing calcite, quartz, pyrite in float, you are in the right ground. Field specimens usually show a test (the hard shell or skeleton of the echinoid) habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify echinoid?+

Mohs hardness is 3-4. It typically shows a dull luster. The streak is white. Common colors include white, gray, tan, brown.

Where is echinoid found?+

Notable localities include England; France; Morocco; USA; Germany.

How much is echinoid worth?+

Typical asking prices fall in the range of $5-50 for common specimens, $100+ for large or rare articulated fossils. Quality, size, and provenance can move individual specimens well outside that range.

What minerals are found with echinoid?+

Echinoid commonly co-occurs with calcite, quartz, pyrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does echinoid form in?+

Echinoid typically forms in sedimentary rocks like limestone and chalk. Working float back to the host body is the standard way to chase a fresh occurrence.

What is echinoid used for?+

Echinoid is used in collector, decorative, educational.

Find echinoid on the map

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