eaglestone

Century Dictionary and Cyclopedia

1. n. A variety of argillaceous oxid of iron, found in masses varying from the size of a walnut to that of a man's head. In form these masses are spherical, oval, or nearly reniform, or sometimes resemble a parallelopiped with rounded edges and angles. They have a rough surface, and are essentially composed of concentric layers. The nodules often embrace at the center a kernel or nucleus, sometimes movable, and always differing from the exterior in color, density, and fracture. To these hollow nodules the Greeks gave the name of eaglestones, from a notion that the eagle transported them to her nest to facilitate the laying of her eggs. Also called aėtites.

Wiktionary

1. n. mineralogy A concretionary nodule of clay ironstone.

GNU Webster's 1913

1. n. (Min.) A concretionary nodule of clay ironstone, of the size of a walnut or larger, so called by the ancients, who believed that the eagle transported these stones to her nest to facilitate the laying of her eggs; aëtites.