Oolite

Oolite (Gr., 'egg-stone'), a variety of limestone, composed of spherical granules of calcic carbonate, which have a concentric and often a fibrous radiating structure. In many cases these granules contain a nucleus or kernel of some foreign substance, such as a grain of sand, round which the successive layers or encrusting coats of calcic carbonate have been formed. Granules of this nature are seen forming in the springs of Carlsbad. A similar oolitic structure has been observed occasionally in the coral-rock forming the surface of modern coral-reefs—which seems to owe its origin to the movement to and fro of grains of coral sand in pools or sheltered places in which the water is highly saturated with carbonate of lime, derived from the decomposition of dead coral. The coarser varieties of oolite are termed Peastone or Pisolite.—For Oolite as the name for a group of strata, see JURASSIC SYSTEM.