A sedimentary rock in which tiger's eye, red jasper, and haematite form alternating layers. It originates from banded iron formation (BIF), roughly 2.2 billion years old—the era when oxygen first began accumulating in the Earth's atmosphere. A record of the Great Oxidation Event, held in stone.

Primarily from Western Australia and South Africa. For all three minerals to deposit simultaneously required iron-rich seawater, a supply of silica, and fluctuations in oxygen concentration. The chemical shifts of a 2.2-billion-year-old ocean, preserved as layers.

A stone that records the history of the Earth's atmosphere. That fact may be grander than any legend.