Turritella Fossil Agate Eocene Green River Wyoming Genuine Specimen Polished Gastropod Shell Fossil 50-100mm with COA

Turritella Fossil Agate – Eocene, Green River Formation, Wyoming, USA

This genuine Turritella Fossil Agate from the famous Green River Formation of Wyoming dates to the Eocene Epoch, approximately 56 to 33.9 million years ago. Combining beautifully preserved fossil gastropod shells within chalcedony agate, this specimen represents one of the most recognisable fossiliferous stones from North America.

You will receive a specimen of the type shown in the photographs, measuring approximately 50–100mm. Each piece has been carefully selected for fossil visibility, structure, and overall display appeal. This is a genuine fossil specimen and includes a Certificate of Authenticity lifetime guarantee generic card. Full sizing is available in the listing photos.

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Geological Age & Green River Formation Context

The Green River Formation is one of the most celebrated Eocene fossil deposits in the world. Spanning parts of Wyoming, Utah, and Colorado, it represents a series of ancient lake basins that developed during the early Paleogene Period.

During the Eocene, this region was dominated by large freshwater lake systems, including Lake Gosiute and Lake Uinta. Fine-grained sediments accumulated in calm water conditions, creating exceptional preservation environments for plants, fish, insects, and molluscs.

The Turritella-bearing agate material originates from sedimentary layers where silica-rich fluids later permeated fossil-rich beds, replacing original shell material and surrounding matrix with chalcedony.

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Fossil Type & Taxonomic Identification

Although traditionally marketed as “Turritella Agate,” many Green River specimens actually contain freshwater gastropods belonging to the genus Elimia, family Pleuroceridae, order Sorbeoconcha (within the class Gastropoda). The historical name Turritella has remained in common usage due to the shells’ elongated, turreted appearance.

These gastropods are characterised by:

• High-spired, tightly coiled shells
• Numerous whorls stacked vertically
• Distinct spiral growth lines
• Conical, tower-like morphology

The preservation within chalcedony allows the shell outlines and internal whorl structure to remain clearly visible, creating a striking contrast between fossil and agate matrix.

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Mineralisation & Agate Formation

Following burial, silica-rich groundwater circulated through the fossil-bearing sediment. Over millions of years, this silica replaced the original calcium carbonate shells through permineralisation and silicification. The result is a fossil embedded within chalcedony, a microcrystalline variety of quartz (SiO₂) belonging to the trigonal crystal system.

The agate component may display:

• Translucent to opaque chalcedony
• Cream, beige, brown, or grey tones
• Subtle banding or cloudy internal texture
• Smooth polished surfaces enhancing fossil detail

This natural silicification process both preserves and stabilises the fossil shells.

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Depositional Environment & Paleoecology

The gastropods preserved in Turritella Fossil Agate lived in freshwater lake environments during the Eocene. These calm, sediment-rich waters supported abundant molluscan populations along lake margins and shallow substrates.

When the snails died, their shells accumulated in large numbers within sedimentary layers. Later silica replacement transformed these shell beds into fossiliferous agate nodules.

The combination of biological abundance and mineral replacement makes these specimens both paleontologically significant and visually distinctive.

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Collecting, Display & Educational Value

Turritella Fossil Agate is highly sought after by fossil collectors, lapidary enthusiasts, and natural history collectors. At 50–100mm, these pieces are ideal for:

• Fossil and mineral collections
• Educational displays demonstrating silicification
• Desktop or cabinet presentation
• Unique geological gifts
• Lapidary appreciation

Each specimen is unique, with variations in fossil density, agate patterning, and shell orientation.

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Authenticity & Presentation

• Genuine Turritella Fossil Agate specimen
• Geological Age: Eocene Epoch
• Formation: Green River Formation
• Locality: Wyoming, USA
• Fossil type: High-spired freshwater gastropods (commonly referred to as Turritella)
• Size range: 50–100mm
• Example shown – you will receive a similar carefully selected specimen
• Includes Certificate of Authenticity lifetime guarantee generic card
• Full sizing available in listing photographs

A remarkable fossiliferous agate from the world-famous Green River Formation, preserving ancient freshwater gastropods in beautifully silicified detail for collectors and enthusiasts alike.