Black Zebra Agate Egg — High-Contrast Banded Chalcedony, Polished, 174g — Field Find

THE FIND
A polished black zebra agate egg, 174g — dark bands move through pale stone in high contrast, disappearing and returning as the egg turns. The pattern reads like a tiny geological map. Something ancient-looking, polished into something remarkably quiet.

WHAT WE KNOW
Agate is a variety of chalcedony — microcrystalline quartz (SiO₂) — recognized for its layered or banded appearance. “Zebra agate” is a descriptive trade name for the high-contrast black, white, and gray banding pattern rather than a separate mineral species. Agate forms when silica-rich hydrothermal fluids fill cavities and fractures in volcanic or sedimentary rock and gradually deposit successive layers of chalcedony on the cavity walls. Changes in mineral chemistry, impurity content, and fluid conditions during each depositional event produce the contrasting bands — black bands are typically produced by manganese oxide or organic carbon inclusions, white bands by pure or near-pure chalcedony. The exact locality of this specimen has not been independently verified. This specimen weighs 174g.

THE STORY
The stone wasn’t choosing between opposites. It had learned to hold them together. Each band in this agate is a depositional event — a period when silica-rich fluid moved through the cavity and laid down another layer. The black and white alternate because the fluid chemistry alternated: more manganese oxide one cycle, purer silica the next. The egg form cross-sections through those layers, turning a depositional sequence into a pattern you can hold.

WHY WE CHOSE IT
The contrast is strong and the banding is well-developed and clearly visible. At 174g it has real weight and presence. A graphically immediate piece — the black and white pattern reads from across a shelf in a way that more subtle specimens don’t. A strong addition to an agate or chalcedony collection.

ABOUT THIS PIECE
Type: Black zebra agate egg (banded chalcedony, polished carving — “zebra agate” is a trade name)
Weight: 174g
Locality: Not independently verified
Condition: Polished carving — please review photographs for banding, contrast, polish, and natural variation.
Quantity: 1 — one of a kind.