Calcareous

Calcareous is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.

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 about 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. Note that not all tests are calcareous; diatoms and radiolaria have siliceous tests.

The molluscs are calcareous, as are calcareous sponges (Porifera), that have spicules which are made of calcium carbonate.

Calcareous grassland is a form of grassland characteristic of soils containing much calcium carbonate from underlying chalk or limestone rock. Species of algae such as the green-segmented genus Halimeda are calcareous.

The term is used in pathology, for example in calcareous conjunctivitis, and when referring to calcareous metastasis or calcareous deposits, which may both be removed surgically.

The term calcareous can be applied to a sediment, sedimentary rock, or soil type which is formed from, or contains a high proportion of, calcium carbonate in the form of calcite or aragonite.

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