Calcareous

Calcareous (/kælˈkɛəriəs/) is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky.

Calcareous is used as an adjectival term applied to anatomical structures which are made primarily of calcium carbonate, in animals such as gastropods, i.e., snails, specifically in relation to such structures as the operculum, the clausilium, and the love dart.

The term also applies to the calcium carbonate tests of, often, more-or-less microscopic Foraminifera.

[1] Additionally, reef-building corals, or Scleractinia, are calcareous organisms that form their rigid skeletal structure through the precipitation of aragonite (i.e., a polymorph of calcium carbonate).

[3] These oozes form slowly under low-energy environments, and necessitate higher seawater saturation states or a deeper CCD (see supersaturation and precipitation vs. undersaturation and dissolution).