Turritella Jasper Identification Guide
A practical guide to identifying Turritella jasper, the opaque fossil-snail silica rock, and telling it apart from Turritella agate and fossil limestone.
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What Turritella Jasper Looks Like
Turritella jasper is the more opaque, jaspery counterpart of Turritella agate: a brown, tan, or grayish silicified rock packed with the spiral shells of freshwater snails (the gastropod Elimia tenera). Where Turritella agate is translucent chalcedony, Turritella jasper has an opaque, earthy jasper groundmass. The shells appear as lighter cream-to-white elongated spirals and ring-shaped cross-sections. Luster is dull to waxy unpolished, becoming smooth and slightly glossy when polished.
Step-by-Step Field-ID Checklist
- Spot the snail fossils. Elongated, high-spired coiled shells and circular slices are the defining clue.
- Judge opacity. A solid, light-blocking brown/tan body indicates jasper rather than translucent agate.
- Check luster. Waxy to dull; polished faces take a smooth shine.
- Hardness test. Will scratch glass and resist a steel knife (silica).
- Acid test. Apply a drop of dilute acid - no fizz confirms silica, separating it from limestone.
- Examine fracture on chips - conchoidal, sharp-edged.
Key Diagnostic Tests
- Mohs hardness: 6.5-7. Scratches glass; not scratched by steel.
- Streak: White.
- Fracture: Conchoidal to splintery, no cleavage.
- Acid: No reaction (key separator from carbonate fossil rocks).
- Magnetism: None.
- Density: ~2.6 g/cm3.
Common Look-Alikes
- Turritella agate: Same fossils and origin but translucent; hold to light - agate glows at the edges, jasper stays opaque. The names are often used interchangeably in the trade.
- Coquina / fossiliferous limestone: Soft (Mohs ~3), fizzes in acid, knife-scratchable.
- Ocean jasper or orbicular jaspers: Have rounded orbs, not spiral shells.
- Petrified wood: Shows wood grain and growth rings, not coiled gastropods.
- Plain brown jasper: Lacks fossils entirely.
The pairing of opaque silica hardness, no acid fizz, and packed spiral snails is diagnostic.
Where It Is Found
Like Turritella agate, the prime source is the Eocene Green River Formation of southwestern Wyoming, USA, with related material from other Western US freshwater (lacustrine) basins. Most cabbing rough and tumbled stones come from Wyoming deposits.
Frequently asked questions
What is the difference between Turritella jasper and Turritella agate?
Both contain the same spiral snail fossils from the same Wyoming deposits. Agate is translucent and glows at thin edges, while jasper is opaque. The terms are often used interchangeably.
How can you tell if it's real Turritella jasper?
Confirm hardness near 7 (scratches glass), no fizz in acid, and the presence of high-spired spiral snail shells in an opaque brown matrix.
What does Turritella jasper look like?
An opaque brown-to-tan silica rock densely packed with cream or white coiled snail shells and ring-shaped shell cross-sections.
Is Turritella jasper a real fossil?
Yes. It contains genuine silicified freshwater snail shells (Elimia tenera), preserved when the lakebed sediment turned to silica.
Turritella Jasper identified by the community
Recent Turritella Jasper specimens identified with Rock Identifier.
