limestone

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Related to calcareous rock: carbonaceous rock

limestone

A rock formed of organic fossil remains of shells, composed mostly of calcium carbonate.

limestone

rock which is largely calcium carbonate, used as a livestock feed when ground. Contains 38% calcium and is used as a calcium supplement. See also dolomite.
References in periodicals archive ?
Occurring on calcareous rocks, concrete, and on lignicolous and rarely, corticolous substrates, this species is widespread across western North America and eastward in the northeastern United States and adjacent Canada.
A widely distributed species in the United States, typically occurring on thin soil in pockets and crevices on calcareous rocks.
venustum exhibit considerable variation in both thickness of the thallus and pruinosity, but all collections at OMA had uniformly 3-septate brown spores and occurred on calcareous rocks.
It is an inconspicuous lichen on calcareous rocks in both exposed and shaded sites.
Found on calcareous rocks, this species is also known from North Dakota and Utah and is characterized by a well developed brownish thallus, convex apothecia, and spores lacking endospore thickenings.
Thomson (1991) characterizes the North American populations as lichens of calcareous rocks in the interior western United States.