''Calcareous'' is an adjective meaning "mostly or partly composed of calcium carbonate
", in other words, containing lime
or being chalk
y. The term is used in a wide variety of scientific
''Calcareous'' is used as an adjectival term applied to anatomical structures which are made primarily of calcium carbonate, in animals such as gastropod
s, i.e., snail
s, 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
. Not all tests are calcareous; diatoms
s are calcareous, as are calcareous sponge
), 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
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
s are usually deposited in shallow water near land, since the carbonate is precipitated by marine organisms that need land-derived nutrients. Generally speaking, the farther from land sediments fall, the less calcareous they are. Some areas can have interbedded calcareous sediments due to storms, or changes in ocean currents.
Calcareous ooze is a form of calcium carbonate derived from planktonic organisms that accumulates on the sea floor
. This can only occur if the ocean is shallower than the carbonate compensation depth
(CCD). Below this depth, calcium carbonate begins to dissolve in the ocean, and only non-calcareous sediments are stable, such as siliceous ooze
or pelagic red clay
Calcareous soils are relatively alkaline
, in other words they have a high pH
. This is because of the very weak acidity of carbonic acid
. Note that this is not the only reason for a high soil pH
. They are characterized by the presence of calcium carbonate in the parent material and may have a calcic horizon, a layer of secondary accumulation of carbonates (usually calcium or Mg) in excess of 15% calcium carbonate equivalent and at least 5% more carbonate than an underlying layer.
List of calcareous rivers
Man made deposits
Calcareous deposits can form in water carrying pipes.
An example of this is Sunday stone
Calcareous coatings, or calcareous deposits, are mixtures of calcium carbonate
and magnesium hydroxide
that are deposited on cathodically protected
surfaces because of the increased pH
adjacent to the surface.