Crinoidal limestone is a sedimentary rock composed primarily of fossilized stem segments and plates from crinoids, ancient echinoderms known as sea lilies. Look for characteristic circular or star-shaped fossil fragments embedded within a calcium carbonate matrix, which are often visible on weathered surfaces or polished slabs. This rock formed in shallow marine environments and is commonly found in geologic strata from the Paleozoic era.

Hardness

Mohs

Luster

Dull

Streak

White

Transparency

Opaque

sedimentarycommon

Crinoidal Limestone

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

Is this crinoidal limestone?

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 crinoidal limestone with a known reference. Crinoidal Limestone sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Crinoidal Limestone leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Crinoidal Limestone typically shows a dull luster.
4
Match the color range
Compare against the expected color range: gray, tan, white, brown.
5
Look at form & habit
Typical habit: massive.

Often confused with

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

metamorphic

Marble

Mohs 3-4

How to tell apart: Luster reads dull on Crinoidal Limestone and subvitreous on Marble.

How to tell apart: Luster reads dull on Crinoidal Limestone and dull to earthy on Fossilized Shells.

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Often found alongside crinoidal limestone

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

All properties

Mohs hardness: 3
Density: 2.5-2.7 g/cm³
Colors: Gray Tan White Brown
Streak: White
Luster: Dull
Transparency: Opaque
Crystal habit: Massive
Cleavage: None
Fluorescence: Often Fluorescent Yellow or White
Rarity: Common
Uses: Decorative, Construction, Collector
Host rock: Marine Sedimentary Deposits
Typical price: $5-50 per specimen

Where rockhounds find crinoidal limestone

Classic worldwide localities

USA
United Kingdom
Germany
Belgium
France

Field-hunting tip

Look in marine sedimentary deposits country — that is the host setting where crinoidal limestone typically forms. If you start seeing calcite, dolomite, quartz in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify crinoidal limestone?+

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

Where is crinoidal limestone found?+

Notable localities include USA; United Kingdom; Germany; Belgium; France.

How much is crinoidal limestone worth?+

Typical asking prices fall in the range of $5-50 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like crinoidal limestone?+

Crinoidal Limestone is most often confused with Marble, Coquina, Fossilized Shells. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with crinoidal limestone?+

Crinoidal Limestone commonly co-occurs with Calcite, Dolomite, Quartz, Clay minerals. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does crinoidal limestone form in?+

Crinoidal Limestone typically forms in marine sedimentary deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is crinoidal limestone used for?+

Crinoidal Limestone is used in decorative, construction, collector.

Find crinoidal limestone on the map

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