Turritella Agate

Turritella Agate is a translucent brown to dark chalcedony densely packed with the spiral shells of ancient freshwater snails, preserved as pale to white silica casts. The contrast between the agatized matrix and the coiled fossil shells gives the stone a distinctive, fossil-rich appearance.

Despite its name, the fossils are not actually Turritella (a marine genus) but the freshwater gastropod Elimia (formerly Goniobasis), and the material is technically a fossiliferous agate or chert rather than a classic banded agate. It comes from the Eocene Green River Formation in Wyoming, USA.

It is popular as a lapidary and collector stone that combines mineral durability with visible fossils.

Turritella Agate formed in the lake beds of the Green River Formation about 50 million years ago, during the Eocene. Vast numbers of freshwater snails lived and died in these ancient lakes, and their shells accumulated in the sediment.

Over time, silica-rich groundwater permeated the shell-rich mud and replaced and cemented the material with chalcedony, agatizing both the matrix and the shells. The result is a hard, translucent brown stone with the fossil snails preserved in cross-section throughout.

The primary source is the Green River Formation of Wyoming, with notable occurrences in the Wamsutter and surrounding areas.

Identify Turritella agate by its brown to nearly black translucent body filled with elongated, spiral snail shells that appear as light-colored coils and cross-sections. Hardness is 6.5 to 7, luster waxy to vitreous, streak white.

The abundant gastropod fossils are diagnostic; few other agates contain such dense, visible shells. Distinguish it from petrified wood (which shows grain and cell structure rather than coiled shells) and from plain brown jasper (opaque, no fossils).

When held to light, thin sections glow translucent brown, confirming the chalcedony content, and the stone readily scratches glass.

Turritella Agate is cut into cabochons, beads, tumbled stones, spheres, and slabs that display the fossil snails, making it a favorite among both lapidaries and fossil enthusiasts. Its hardness lets it take a good polish and wear well in jewelry.

It has educational and collector appeal as an attractive, polishable fossil rock, and well-preserved or unusually dense shell material is especially sought.

Metaphysically it is associated with grounding, ancestry, and connection to the past, fitting its fossil nature, though these meanings are traditional rather than scientific.