fossil

Calamites fossil

Calamites (extinct genus of arborescent horsetails)

Hardness: 3-4 (matrix usually shale or siltstone); Color: Dark gray to black (carbonaceous) or rusty brown; Luster: Dull to earthy; Structure: Distinctive vertical ribbing and horizontal nodes/joints similar to bamboo.

Hardness: 3-4 (matrix usually shale or siltstone)
Color: Dark gray to black (carbonaceous) or rusty brown
Luster: Dull to earthy

Identified July 4, 2026More fossil →

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Physical properties

Formation & geological history

Formed during the Carboniferous period (approx. 300-360 million years ago) in swampy, coal-forming environments. Calamites were giant horsetail trees that grew up to 30 meters tall.

Uses & applications

Predominantly used for scientific study and personal collections; also a major contributor to global coal deposits.

Geological facts

Calamites are ancestors of the modern horsetail (Equisetum). The fossil seen here is often an internal cast of the hollow pith cavity of the stem. The location (Louisville, KY area) is famous for the Falls of the Ohio and similar Paleozoic sedimentary exposures where such fossils are common.

Field identification & locations

Identify by looking for the 'jointed' look with parallel vertical ridges. In the field, look for these in sedimentary layers (shales/sandstones) near coal seams or river banks in the Ohio Valley region.

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