Crinoids are ancient marine echinoderms whose stalk-like stems are frequently found as stackable, disc-shaped fossil segments in Paleozoic limestone. Collectors often look for complete 'heads' or calyxes, which are highly prized compared to the abundant loose stem segments found in many sedimentary deposits.
Spotting crinoids in the field
Field marks- 1
Stacks of small round or star-shaped discs, which are the stem segments
- 2
Individual discs have a central hole and often a star-shaped canal
- 3
Complete specimens show a cup and feathery arms atop the stem
Most crinoid material you find is disarticulated stem, and loose columnals are among the most common fossils in Paleozoic limestone anywhere in the Midwest and Appalachians. Whole crowns with the cup and arms attached are a different order of rarity and are what serious collectors want. Look in limestone road cuts, quarry spoil and creek beds, and check weathered surfaces where the rock has etched back and left the fossils standing proud.
Straight answers
- Is it worth cutting?
- Crinoidal limestone cuts and polishes into attractive slabs full of cross-sectioned stems. Individual specimens are prepared, not cut.
- What is it really worth?
- Loose stem pieces are worthless commercially and excellent for teaching. Complete crowns, especially prepared ones from Crawfordsville in Indiana, are valuable.
- Can you legally keep it?
- Invertebrates, so ordinary reasonable-amount personal-use collecting applies on BLM and Forest Service land. Most classic localities are private quarries requiring permission.
Where it is worth going
- CrawfordsvilleMontgomery County, Indiana
World-famous for complete crinoid crowns. The productive sites are private and access is by arrangement only.
Often confused with
Crinoids vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Horn corals are single cone-shaped structures with internal radiating septa. Crinoid stems are stacked discs with a central canal.
How to tell apart: Bryozoans form lacy or branching colonies covered in tiny pores, without the disc-stack structure.
Often found alongside crinoids
Minerals reported to co-occur with crinoids. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 3-4
- Density
- 2.7-2.9 g/cm³
- Streak
- White
- Luster
- Dull to Vitreous
- Transparency
- Opaque
- Crystal habit
- Stem Segments, Calyx, Disc-like Ossicles
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Decorative, Paleontological Study
- Host rock
- Limestone, Shale, Marine Sedimentary Strata
- Typical price
- $5-50 for small plates, $100-500+ for large museum-grade specimens
Where rockhounds find crinoids
7 mapped spotsClassic worldwide localities
- USA (Midwest)
- Germany
- United Kingdom
- Canada
- Morocco
Field-hunting tip
Look in limestone, shale, marine sedimentary strata country, the host setting where crinoids typically forms. If you start seeing calcite, pyrite, quartz in float, you are in the right ground. Field specimens usually show a stem segments, calyx, disc-like ossicles habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Ohio, Wisconsin, New York. Start trip planning there.
Common questions
How do you identify crinoids?+
Where is crinoids found?+
Can I find crinoids in the United States?+
How much is crinoids worth?+
What rocks look like crinoids?+
What minerals are found with crinoids?+
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What is crinoids used for?+
Find crinoids on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
