Banded Onyx Egg — Layered Chalcedony, Natural Banding, 254g — Field Find

THE FIND
A polished banded onyx egg, 254g — layered chalcedony with contrasting bands that shift as the egg turns. The polished form brings out the contrast between the layers while preserving the natural character of the stone. The larger of two banded onyx eggs currently in the Found in the Field collection.

WHAT WE KNOW
Onyx is a variety of banded chalcedony — microcrystalline quartz — in which the banding runs parallel and straight (distinguishing it from agate, where banding can be curved or irregular). The banding develops through successive deposition of silica-rich mineral fluids in rock cavities, with each layer representing a depositional event. Onyx in the trade is a frequently misapplied name: much commercial “black onyx” is actually dyed agate or chalcedony, and many stones sold as “onyx” (particularly Mexican and Pakistani “onyx”) are actually banded calcite or travertine rather than true chalcedony onyx. This specimen is presented as banded onyx chalcedony based on its appearance and catalog identification; material identification has not been independently laboratory verified. The exact locality and provenance of this specimen have not been independently confirmed. This specimen weighs 254g.

THE STORY
The banding in chalcedony onyx is a geological record of repeated mineral deposition — each layer represents a period when silica-rich groundwater moved through the cavity and deposited material on the cavity wall. The color variation between bands reflects differences in mineral impurities or iron content in the fluid at the time of each deposition. In a polished egg, those layers become a cross-section through that depositional history — a record of how many times the conditions were right for another layer to form.

WHY WE CHOSE IT
The banding is natural and clearly visible, and the polished finish brings out the contrast between the layers. At 254g it has substantial presence as a display object — the larger scale gives it more weight and visual authority than the smaller companion piece. A grounding, architectural piece for a mineral or lapidary collection.

ABOUT THIS PIECE
Type: Banded onyx egg (polished chalcedony carving, presented as onyx based on appearance; not independently verified)
Weight: 254g
Locality: Not independently verified
Condition: Polished carving — please review photographs for banding, polish, and natural variation.
Quantity: 1 — one of a kind.