Conodonts, however, are composed of calcium phosphate, as in the skeletons of vertebrates.
Unlike the shells of its relatives, the lingulids, the obolus shells were composed of calcium carbonate.
These deposits are generally composed of calcium carbonate dissolved from the surrounding limestone by groundwater.
Unlike those of hydroids, hydrocoral skeletons are composed of calcium carbonate and are internal by virtue of being shallowly penetrated by channels of living tissue.
Hard parts of animals, primarily known from Africa and China, are mainly dwelling tubes composed of calcium carbonate and other compounds.
Samples for geochemical analysis are taken by the whole-rock method or by the retrieval of fossils with unaltered shells composed of calcium carbonate.
The hard framework of the colony is composed of calcium carbonate, which formed the closely packed tubelike structures that housed the individual animals in the Prasopora colony.
Stromatoporoids (a type of sponge with a layered skeleton composed of calcium carbonates) such as Amphipora were common rock builders in the mid-Devonian of the Northern Hemisphere.
The blackboard crayon, or chalk, that is used in classrooms is commonly composed of calcium carbonate, kaolin clay, oleic acid, and caustic soda.
Prior to copulation of certain land snails, a dart composed of calcium carbonate is propelled forcefully from the gonopore of each of the mating individuals and lodges in the viscera of the mate.
Chief among the last group are the tests of foraminiferans, pteropods, and coccolithophores that are composed of calcium carbonate and those of diatoms and radiolarians that are made of silicon dioxide.
