Rock Identifier
Turritella Agate / Fossiliferous Limestone (Elimia tenera (commonly mislabeled as Turritella in chalcedony/calcite matrix)) — fossil
fossil

Turritella Agate / Fossiliferous Limestone

Elimia tenera (commonly mislabeled as Turritella in chalcedony/calcite matrix)

Hardness: 6.5-7 (if silica-rich chalcedony matrix) or 3 (if calcite limestone matrix). Color: Dark brown, grey, to black with pale white or tan coiled snail shells. Luster: Dull to waxy or vitreous. Cleavage: None in agate; rhombohedral in calcite portions.

Hardness
6
Luster
Dull to waxy or vitreous
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Physical properties

Hardness: 6.5-7 (if silica-rich chalcedony matrix) or 3 (if calcite limestone matrix). Color: Dark brown, grey, to black with pale white or tan coiled snail shells. Luster: Dull to waxy or vitreous. Cleavage: None in agate; rhombohedral in calcite portions.

Formation & geological history

Formed during the Eocene epoch (around 50 million years ago) in freshwater lakes (such as the Green River Formation in Wyoming). High concentrations of freshwater snails were buried and replaced or embedded in silica/calcite-rich sediment.

Uses & applications

Used extensively for lapidary work, cabochons, decorative carvings, educational fossil collections, and jewelry.

Geological facts

Despite being traditionally called 'Turritella Agate', the fossil snails contained within are actually 'Elimia tenera', a freshwater species, whereas true Turritella are marine gastropods.

Field identification & locations

Identified by the distinct spiral, spiral-coiled shell cross-sections exposed on dark matrix surfaces. Commonly found in southwest Wyoming, USA. Collectors value specimens with high shell density and complete coils.

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