eozoön

Century Dictionary and Cyclopedia

1. n. A name given in 1865 by the geologists of the Canada survey to a certain aggregate of minerals, viewed by them as a fossilized organic body, belonging to the Foraminifera. The best-characterized specimens of so-called Eozoön exhibit on the polished surface to the naked eye alternating bands of grayish and greenish color. These bands, which are generally from one to four tenths of an inch in thickness, vary considerably as regards the regularity of their occurrence, and between them are frequently seen layers of a mineral mȧde up of fine parallel fibers. The whitish mineral is usually calcite; the greenish, serpentine; and the fibrous bands are the variety of serpentine called chrysotile. Microscopic examination has shown that the whole is an alteration-product of various minerals. The calcite has frequently running through it, and grouped in a great variety of ways, branching forms, which were supposed by the advocates of the foraminiferal nature of the Eozoon to represent the canal-system of that form of organisms. This same structure has, however, been frequently observed in minerals forming part of rocks of undoubted igneous origin, as well as in those occurring as veinstones, and there can no longer be any doubt as to the inorganic nature of the Eozoon. This supposed foraminifer, having been found in rocks called at that time Azoic, and later Archæan, was believed to be the oldest recognized organic form, and to represent the “dawn of life”; hence the generic name. The supposed species was called E. canadense by J. W. Dawson.

Wiktionary

1. n. paleontology, dated A pseudofossil with banded structures of coarsely crystalline calcite and serpentine.

GNU Webster's 1913

1. n. (Paleon.) A peculiar structure found in the Archæan limestones of Canada and other regions. By some geologists it is believed to be a species of gigantic Foraminifera, but others consider it a concretion, without organic structure.