Calamites Stem Impression
Calamites sp. (cf. C. suckowii or C. cistii) • Plant body fossil; carbonaceous impression or mold of arborescent lycopsid/sphenopsid
Geological Period
Carboniferous (Pennsylvanian sub-period)
Estimated Age
298 to 323 million years ago
Preservation Type
Carbonization/Impression. The organic material has largely been replaced by iron-rich minerals or leaves a thin carbon film, resulting in a detailed surface mold on the sediment.
Condition Assessment
Fair to Good. The ribbing is distinct, but the specimen is fragmentary, lacking nodal junctions or branching points that would increase its value and scientific utility.
Taxonomic Classification
Kingdom: Plantae, Phylum: Pteridophyta, Class: Equisetopsida, Order: Equisetales, Family: Calamitaceae, Genus: Calamites
Morphological Description
The specimen shows characteristic longitudinal ribbing and grooves typical of the external vascular structure or internal pith cast of a Calamites trunk. The ribs are parallel, slightly flattened, and separated by shallow furrows. No distinct nodes (joints) are visible in this specific fragment, but the linear texture is diagnostic of giant horsetail stems.
Rock Matrix
Iron-rich Sideritic Mudstone or Siltstone, identified by the characteristic reddish-orange/rust-colored oxidation (limonite/hematite staining) typical of 'Coal Measures' flora.
Formation & Location
Commonly found in the Mazon Creek formation (Illinois, USA), the Breathitt Group (Kentucky/Appalachia), or the Coal Measures of Northern England and Germany.
Size & Dimensions
Approximately 5-8 cm in length; this represents a small fragment of a plant that could originally reach heights of 30 meters.
Value & Rarity
Estimated Market Value
$10.00 - $25.00 USD
Auction Estimate
$15.00 - $40.00 USD (typically sold in bulk lots or as educational specimens)
Rarity Assessment
Common. Calamites remains are among the most abundant plant fossils found in Carboniferous coal-bearing strata worldwide.
Scientific Significance
Provides evidence of the 'Coal Forest' ecosystems of the Paleozoic. Calamites were significant contributors to carbon sequestration and the formation of modern coal seams, dominating swampy, equatorial environments.
Preparation Recommendations
No invasive preparation needed. It should be kept dry to prevent further oxidation of the iron-rich matrix. Should be stored in a padded box to prevent the edges of the brittle siltstone from crumbling.
Notable Features
The striking iron-oxide coloration provides high contrast for the ribbing. The texture clearly illustrates the inner anatomy of these extinct giant horsetails, which differ from modern Equisetum primarily in their secondary xylem growth.