Horsetail fossils, particularly the genus Calamites, are the segmented, reed-like remains of giant prehistoric plants from the Carboniferous period. Collectors look for the distinct vertical ribbing and nodal joints preserved in sandstone or shale matrices, which clearly show the internal structure of these ancient vascular plants.
Is this horsetail fossil?
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 horsetail fossil with a known reference. Horsetail Fossil sits at Mohs 3-5, softer than the next harder reference, harder than the previous one.
- 2Name the organismDecide what left the fossil before worrying about the rock. Organism: Extinct tree-like horsetails (genus Calamites). Age: Carboniferous to Permian.
- 3Check the preservationPreservation: Casts of the stem, most commonly internal pith casts. That controls the weight, the hardness and how the piece takes a polish.
- 4Read the lusterHold the specimen under a strong light. Luster: dull.
- 5Match the color rangeCompare against the expected color range: gray, brown, black, tan.
Often found alongside horsetail fossil
Minerals reported to co-occur with horsetail fossil. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 3-5
- Density
- 2.0-2.6 g/cm³
- Luster
- Dull
- Transparency
- Opaque
- Rarity
- Common
- Uses
- Collector, Educational, Display
- Host rock
- sedimentary shale and coal measures
- Organism
- Extinct tree-like horsetails (genus Calamites)
- Age
- Carboniferous to Permian
- Preservation
- Casts of the stem, most commonly internal pith casts
Where rockhounds find horsetail fossil
Classic worldwide localities
- Pennsylvania
- West Virginia
- Ohio
- Nova Scotia
- Germany
- Czech Republic
Field-hunting tip
Where it forms: sedimentary shale and coal measures. If you start seeing coal, sandstone, shale in float, you are in the right ground.
Common questions
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Find horsetail fossil on the map
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