Calamites Stem Impression (Horsetail relative)
Calamites sp. (Specific species determination requires better node visibility, cf. Calamites cisti) • Plant body fossil (Impression/Compression) of an arborescent sphenopsid
Geological Period
Carboniferous Period (likely Pennsylvanian subperiod)
Estimated Age
298.9 to 323.2 million years ago
Preservation Type
Impression with residual carbonization; the organic material has largely decayed leaving a physical imprint in the sediment.
Condition Assessment
Fair to Good; the ribbing is distinct, but the specimen is fragmentary and lacks diagnostic nodes (joints) which are critical for species-level ID.
Taxonomic Classification
Kingdom: Plantae; Phylum: Pteridophyta; Class: Equisetopsida; Order: Equisetales; Family: Calamitaceae; Genus: Calamites
Morphological Description
Specimen shows characteristic longitudinal ribbing and parallel grooves representing the external surface of a trunk or branch. The ribs are linear and separated by narrow furrows. Some carbonaceous film remains (black spots).
Rock Matrix
Iron-stained silty shale or fine-grained sandstone. The reddish coloration indicates the presence of hematite or limonite (iron oxides).
Formation & Location
Commonly found in the Pottsville Formation (USA), the Coal Measures (UK), or similar Carboniferous fluvio-deltaic deposits globally.
Size & Dimensions
Approximately 5-8 cm in length; this represents a small fragment of a plant that could reach 30 meters in height.
Value & Rarity
Estimated Market Value
$10 - $25 USD
Auction Estimate
$15 - $40 USD
Rarity Assessment
Common; Calamites fragments are among the most abundant plant fossils found in Carboniferous coal-bearing strata.
Scientific Significance
Provides evidence of ancient swamp forest ecosystems (Coal Forests). Calamites were major contributors to global coal seams and illustrate the evolution of vascular plant size.
Preparation Recommendations
Keep dry; no chemical cleaning needed. Use a soft brush for dust. Iron-rich shale can be brittle, so avoid high humidity to prevent oxidation/fragmentation.
Notable Features
Features distinct parallel longitudinal striations and localized carbonaceous residue showcasing the transition between organic material and mineralized impression.