sedimentary (silicified fossiliferous chalcedony)

Turritella Agate (Elimia Agate)

Silicified Elimia tenera (formerly misidentified as Turritella)

Hardness: 6.5-7 (Mohs scale); Color: Dark brown to black matrix with white/cream fossil inclusions; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.60-2.65

Hardness: 6
Luster: Vitreous to waxy

Identified March 24, 2026More sedimentary (silicified fossiliferous chalcedony) →

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Physical properties

Formation & geological history

Formed during the Eocene Epoch (approx. 50 million years ago) in freshwater lake environments of the Green River Formation. The shells of Elimia tenera snails were replaced by silica-rich groundwater through a process of permineralization.

Uses & applications

Primary use is in lapidary arts for cabochons, beads, and bookends. It is highly valued as a decorative collector specimen and in holistic jewelry as a 'stone of connection to the past'.

Geological facts

Despite its common name, the fossils aren't actually Turritella (a marine snail) but Elimia tenera (a freshwater snail). The rock is famous for its 'frozen in time' appearance, capturing mass mortality events of ancient snails.

Field identification & locations

Identify by looking for spiral-shaped fossil cross-sections embedded in a dark, hard chalcedony matrix. It is found almost exclusively in the Green River Formation of Wyoming, USA. For collectors, look for high fossil density and high-polish potential.

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Silicified Elimia tenera (Fossiliferous Chalcedony)

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Fossiliferous Limestone (Chertified Limestone)

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